15 ORGANIC CHEMISTRY 2
water grease separates from surface The calcium and magnesium salts o f this d etergent
molecul es m o lecule arc water soluble, so the prob lem o f scum
.-~·······....and isheld in suspension is solved. Very many o f our washing powd ers (and
liquid s) contain this type o f substance.
with • • Ma nufacture of soap less det e rge nts
agitation ••••••••
grease Soa plcss detergen ts arc detergents that can be u sed
Fi gure 15.1 7 Soap dissolves grease like this. m o re cffCctivcly than soap , particularly in hard water
areas (sec C h apter 11 , p. 188 ). They arc fairl y cheap
On the other hand, the hyd rophilic ionic head group to m ake and arc rapidly replacing soaps.
is n ot attracted to the grease but is stron gly attract ed
to the water m olccuks. W hen the water is stirred , the Th e gen eral process involves, initially, the reactio n
grease is slowly released and is completely surrounded o f a lo ng, straig ht-ch ain alkcnc, such as d odcccn c
by the soap m olecules. The grease is, therefore, (C H J( C H 2 )9C H =CH 2) , with ben zene.
'solubiliscd ' and rem oved fr o m th e dish. Th e soap is
able to rem ove the grease because o f the combinatio n benzene + dodecene dodecylbe nzen e
o f th e covalent and io nic bo nds present.
C6H dl) + CH iCH2~CH=CHi{1) ---> C6H s(C H2)11CH3(l)
Soap less det e rge nts
1l1c m olecular formula o f d o dccylbcn zenc is C 18H 30 .
In C hapter 11 , p. 188, we discussed the way in This compound is then reacted with co ncentrated
which , in hard water areas, an insolu ble scum
fo rms when soap is used. This problem has been sulfuri c acid to g ive a com pound th at is kn own as a
overcom e by the d c,,d o pmcnt o f synthetic soap less
detergents . These new substan ces d o n ot fo rm sulfo ni c acid.
scum with hard water since they d o no t react with
Ca2+ and Mg2+ present in such water. Furth ermo re, dodecylbenzene + sulfuric ---> dodecylbenzene + water
these new soapless deterge nt m o lecules have been
desig ned so that they arc bio degradable . Bacteria acid sulfonicacid
readily break d own th ese new mo lecules so that they
d o n ot persist in the enviro nment. Fin ally, this is reacted with the alkali sodium
h yd roxide, N aOH.
Sodium alkyl ben zen e sulfo n atcs were d evelo ped
in the early 1970s. The stru cture o f sodium dodecylbenzene + sodium sodium + water
3-d odccylbcn zenc sulfatc, C 18H 29S0 3 N a, is given dodecy lbenzene
below. sulfo n i c a c i d hydroxide + H10 {t)
sulfonate
C1~H19S03H(><i) + NaO H(oq) -> Cu H19S03-Na+(oq)
(soapless detergent )
These d ays, soa plcss detergen ts such as thi s arc to b e
found in m ost washing powders and liquids.
Questions
1 What class of organic compound do substances like
glyceryl stearate belong to?
2 What do you understand by the terms:
a hydrophobic?
b hydrophilic?
c saponification?
3 What is the main advantage of detergents over soaps?
Condensation polymers
• Condensation polymers This is the same amide link as fo und in proteins
(p. 24 3 ). It is o ften called the peptide link. This
In Ch apter 14 (p. 226 ) you studi ed th e diffCrcnt type o f polymerisatio n, in which two kinds o f
additio n po lym ers produ ced fro m alkcnes . N ot all m o n om er unit react, results in a chain o f the type :
po lymers arc fo rmed by additio n reactio ns, tho ug h .
Som e arc produced as a result o f a different type - A-B-A-B-A-B-A-B-A-B-
o f reacti on. In 1935 Wallace Carothers discovered
a different sort o f plastic wh en he develo ped th e G en erally, po lyamidcs have the structure
therm o plastic, nylo n. Nylo n is made by reactin g two
different ch emicals together, unlike po ly(cthenc ) 0 00 0
which is m ade o nly fr o m m o no mer units o f ethene .
Po ly(cthcnc ), fo rmed by addition polymerisatio n, II II II II
can be represented by: -C~ C-N----c::::J-N-C~ C-N----c::::J-N-
1I II
HH HH
- A-A-A-A- A- A-A-A-A-A- \.Yh cn nylon is mad e in indu stry, it fo rms as a solid
which is melted and fo rced throu gh small ho les
wh ere A = m on o m er. (Fi gure 15.19). Th e lo n g filam ents cool and solid
The starting m o lecules for nylo n are m o re nylo n fibres arc produced which arc stretched to
complicated than those for poly(cthen c) and arc align the polym er m o lecules and then dried . The
called 1,6-diamino hcxanc and hcxancdio ic acid . resulting yarn can be woven into fabri c to make
shirts, ties, sheets and parachutes o r turned into
1,6 - diaminohexane + hexanedioic acid ropes o r racket strings fo r tennis and badminto n
H,N(CH,), Nf-L, rackets. Th e annu al wo rldwid e productio n o f nylo n
is expected to reach 6 millio n to nnes by 2015.
The po lymer chain is m ade up fr o m the two starting
m o lecules arranged alternately (Figure 15 . 18 ) as
these mo lecules react and therefore link up . Each
time a reacti on takes place a m olecule o f water is
lost.
This sort o f reactio n is called condensation Figure 15.19 Nylon fi bre is formed by forcing molten pla stic through
polymerisation. Thi s differs fr o m additio n hundreds of tiny holes.
polymerisatio n, wh ere there is o nly on e product.
Because an amide link is fo rmed during the We can o btain different po lym ers with different
polymerisatio n, nylo n is known as a polyamide. pro perties if we carry out condensatio n
polym erisatio n reactio ns between o ther m o no m er
mo lecu les. Fo r example, if we react cthan e-1 ,2-dio l
with bcn zcn e-1 ,4-dicarboxylic acid , then we produce
a polym er called Tcrylcnc.
15 ORGANIC CHEMISTRY 2
ethane- 1,2-diol + benzene- 1,4-dicarbm.)'lic acid Alo ng with fats and proteins, th ey arc amo n g th e
H O (C Hz)zOH main constituents o f food .
j H OO C{C 6H JCOO H
Starch occurs in potatoes, rice and wheat. Glucose,
This ester link is the sam e linkage as in fut s. fro m which starch is polymerised , belo n gs to
Generally, po lyesters have th e structure a group o f simple carbo h ydrates known as
monosaccharides. Th ey arc sweet to taste and
0 00 0 soluble in water. Starch belo ngs to the m ore
II II II II complicated group o f carboh ydrates known as
- C~ C- 0----c::::J-0 - C~ C- 0----c::::J-0 - polysaccharides. Starch d o cs no t fo rm a true
solutio n and it d ocs n o t have a sweet taste. W ith
Like nylon , Tcrylene can b t: turned into yarn, which iodine it gives an intense blue colo ur (n early black),
can then b e woven. Tcryknc clo thing is generally which is used as a test fo r starch or iodin e itself
softer than that madt: fro m n ylo n but b oth arc hard ( Figure 15.20).
wearing . Becau se an ester link is form ed during tht:
po lym erisation , Tcrylcnc is kn own as a polyester.
Fats possess the same sort o flinkagc as Tcrylem::
but have different units. Fo r a forthcr discu ssio n sec
p. 238.
Questions
1 Draw the structure of the repea ting units found in :
a nylon b Terylene.
2 Explain the differences between an addition polymer
and a condensation polymer.
• Some biopolymers
St a rch
Starch is a b iopolymer o r nan1ral polymer. It is a Figure 15.20 A darkblue---blackcolourisproducedv.-hendiluteiodine
co ndensatio n po lym er o f glucose, a typ e o f sug ar. It solution is applied to starch, for example in a potato.
is o ften produ ced as a way o f sto rin g energy and is
form ed as a result o f pho tosynthesis in green plants.
carbon + water phorosymh~i, glucose + oxygen
di oxide
, uolig:ht/ Hydro lys is o f st arc h
cblorophyU
(in s ,.eopW>u)
glucose starch + water Starch can be broken d own in two ways, both o f
n H 20 (!) which take place in th e presen ce o f water. H en ce
nC6H 12 0 6(aq) ----> (C6 H 100 5 ),.(s) + th e reactio n s are known as hydrolysis reactio n s.
H yd rolysis o f starch is the key reacti o n that enables
Starch can b e represented by u s to u se thi s en ergy so urce. lf starch is boiled
for about one ho ur with dilute hyd rochloric acid,
- 0---c::::J-O---c::::J-O---c::::J-O- it is broken d own into its m o n om ers, g lu cose
m o lecules.
Bo th starch and g lucose arc carbohydrates, a class
o f naturally occurring o rgani c compo unds which can starch ~ glu cose
be represented by the general formula (CH 2 0 )x. heat
(C 6 H 100 5),.(s) + 11H20 (1) ~ 11C6H 12 0 6(aq)
Some biopolymers
If starch is mixed with sali va and left to stand for ~ \i H
a few minutes, it will break d own to maltose, a H - C' - H
disaccharide (that is two jo ined m o nosaccharid cs) . H 2N - r - cooH H 2N - T - CO O H
The en zym e present in t he saliva, called amylase, I
catalyses this hyd rolysis reaction. HH H 2N - T - C O O H
ge nera l glyci n e H
alanine
starch + water in saliva ~ maltose
En zym es arc very effi cient natural catalysts present Amino acid s arc the building blocks o f proteins.
in plants and animals. TIK')' d o n ot require hig h Similar to nylo n (sec p. 24 1) proteins arc
temperatures to break d own the starch to maltose. In polyamidcs, as they con tain the - C ONH- group ,
humans, a salivary amylase breaks d own the starch in which is called the amid e or, in the case o f
o ur fo od . If you ch ew o n a piece o f bread for several proteins, the peptide link. Proteins arc fo rmed by
minutes, you will n o tice a sweet taste in your m o uth. condensatio n polym erisatio n.
The above hydrolysis reactio ns arc summarised in
Fig ure 15 .21. glyci n e alani ne
starch H H
- 0 ----{=:J- 0 ----{=:J-0 ----{=:J-0 ----{=:J-0 ----{=:J-0 ----c:::J- 0 - H ~N - C' - COO H H 2N - 9' - c o o H
-I CH,
H
·~~ I \ ~'.'.ym, HO H
hydrol/ \ d ro lysis
I II I
H 2N - T - c - ~ - T - cooH + H 2o
HO--c:J- OH HO----c:::J- OH HO--c:J---0 ----c:::J-OH H H CHJ
HO--c:J- OH HO----c:::J- OH HO--c:J---0 ----c:::J-OH
HO--c:J- OH HO----{=:J- OH HO--cJ-0 ----{=:J-OH a dipeptide
glucose maltose (composed of two amino acids joined together)
(~H120 i;) (C12H22 0 11l Protein chains formed by the reaction o f m any
amino acid m o lecules have the general structure
Figure 15.21 Starch produces glucose or maltose depending on the type shown bdow.
of hydrolysis used. Using chromatography it is possible to separate and
identify the products of the different styles of hydrolysis.
HH O R HH O
I I II I I I II
Questions - N- C- C- N- C- C- N- C- C-
1 In the hydrolysis of starch, how, using a chemical 1 I I II I
test. could you tell whether all the starch had been
hydrolysed? R HHO R
2 Describe a method you could possibly use to identify the Further reacti o n with many m o re amino acids takes
products of the different types of hydrolysis. place at each end o f each m o lecule to produce
the final protein (Fi gures 15.22 and 15.23 ). For
Amin o acid s a m olecule to be a p rotein, there must be at least
100 amino acids involved. Below this number, they
There arc 20 different amino acids and they each arc called po lypeptides . Proteins make up so me 15%
possess two fun ctio nal groups. One is the carbo xylic o f o ur body weig ht.
acid group, - C OO H . The o ther is the amin e group,
- NH2 . Th e two amin o acids sh own at the to p o f the - 1N---[J- cTI- N- [J-c- IN---[J-cTI-
n ext column arc glycine and alanine .
1 II
H0
Figure 15.22 Generalstructureof a protein.
15 ORGANIC CHEMISTRY 2
A chain COOH
B chain
10 15
30 25
Figure 15.23 The structure of a prot ein - human insulin (the different coloured circles represent different amino acids in this protein).
Proteins fall broadly into two groups: they can be
fib rou s or g lo bular.
• Fibrous proteins - these have linear m o lecules,
arc insoluble in water and resistant to alkalis and
acids. Collagen (in tendon s and mu scles), keratin
(in nails, hair, ho rn ;md feathers) and dastin (in
arteri es) arc all fib rous proteins.
• Glo bular proteins - th ese have complicated
three-dimen sional structures and arc soluble in
water. Th ey arc easily affected by acids, alkalis
and temperature in crease, wh en they an: said to
be d en atured . Casein (in milk), albumen (in egg
white) and en zym es arc cxampks o f glo bular
p r o t ei n s.
Analysis of the products of the hydrolysis of Figure 15.24 Amino acids can be separated and identified by TLC.
proteins
lf you arc tryin g to sh ow only the presence o f a
H ow can you d etermine which amino acid s arc protein , a quick test to carry o ut is known as the
present in a particular protein ? This in volves Biuret test . A mixture o f dilute sodium hyd roxide
hyd rolysis o f the peptide (amide) bo nd s in th e and 1% coppcr(n) sulfatc solutio n is sh aken with
p rotein so that th e individual amin o acids are a sample o f th e material under test. If a protein is
released. This can o nly be d o n e by h eating present, a purple colo ur appears after abo ut three
the protein with dilute hydrochlo ric acid. Th e minutes ( Fig ure 15.2 5 ).
mixture o f amino acids is then separated by thin
layer ch romatography (TLC) (Figure 15 .24 ) or
elect rophoresis. In b o th cases, a locating agent
(Chapter 2 , p. 2 3), such as ninhydrin, is used. Thi s
en sures that the spots o f amino acid are visible.
Some biopolymers
a Testingfor a protein. bAddingdilute sodiumhydroxide. .-lliilM-..L -
Figu re 15.26 Crick and Watson based this model for DNA on X-ray
studies performed by Rosalind Franklin and chemical anatjsis.
Gen es are th e units o f heredity that contro l th e
characteristics o f organism s. A gene is made o f
DNA. N o t wo individuals have the same DNA
sequence. DNA ' fin g erprintin g' h as becom e a very
powerfol forensic science tool in the im'estigatio n o f
crime (Figure 15.27 ).
c Adding 1% copper(•) sulfate. Figure 15.27 ldenticalpatternssho'NnbyDNAfingerprintingcan
identify the crim inal.
Figure15.25 TheBiuret test.
Questions
DNA
1 Which two functional groups do amino acids possess?
Dem.'.)'ribonucleic acid (DNA) belo ngs to a groui:; 2 How many amino acids have to be involved before the
o f chemicals called the nucleic acid s (Figure 15 .26)
They are also bio po lymers. DNA controls the prate biopolymer is called a protein?
synthesis within your cells. When you eat a food 3 Name the process by which the individual amino acids in
containing proteins, su ch as m eat o r cheese, your
digestive enzymes break down the proteins present a protein are released by reaction with a dilute acid.
into individual amino acids. The DNA in your cells 4 Explain how DNA fingerprint ing may be used in
controls the o rder in which the amino acids arc
rep olym erised to make the proteins you need ! paternity suits.
15 ORGANIC CHEMISTRY 2
• Pharmaceuticals Tabl e 15.4 Commonly available drugs. Fo r the treatme nt of
Pharmaceuticals arc drugs that arc prepared and sold Name and stru ctu re Headaches, mild pain, heart
with the intentio n o f t reating illness . A drug is any disease
substance, natural o r synthetic, which alters the way Aspirin
in which the body works. Th ere arc m an y categories 0
o f drugs . The fo llowing are som e exam ples . II
• An aesth etics - these indu ce loss o f feel ing and/or ( n ' T C- 0 - H
con scio u sness, fo r example flu o thanc.
~ o - c -- CH3
• An algesics - these rel ieve pain, fo r example aspirin. Paracetamol
• Antibio tics - these ;1rc substan ces, fo r exam ple II
0
penicillin , originally produ ced by micro-o rganism s,
which arc u sed to kill bacteria. H owever, m ost Headaches,mildpain
antib iotics are now m ade in ch emical labo ratories,
fo r example carbcnicillin. Ibuprofen Arthritis,fever,mildto
• Sedatives - th ese indu ce sleep , fo r example moderate pain
ba r biturates . II 'I-@O - I'CH3 HH
• Tranq uillisers - th ese will g ive relief fr o m an xiety, C- COOH High blood pressure
fo r exam p le Valium . H- C- C {hypertension)
CH 3 H CH 3
There arc, of course, many other types of drug
availa ble which have very specific u ses. For exam p le, Penicillin A variety of bacterial
mcthyldo pa was d eveloped to relieve hyperten sion infections
( hig h blood pressure ), and antihistamines were 0H
developed to hel p control travel sickness, h ayfever Feelings of anxiety or
and allergic reactio ns. NI S CH 3 depression
Th e pharmaceutical industry is o ne o f the CH3 -c-N1 1 · 'r( CH
most im portant parts o f the ch emical indu stry
and is a major consumer o f the produ cts o f th e )-- N~ l
petrochemical industry. It is a high-profit industry
but with very hig h research and d evelopment costs. 0 C=O
For exam ple, it costs in excess of£ 100 milli on to
discover, test and get a single dru g o n to the m arket. I
H
T oday, th e pharmaceutical in d ustr y could be called
the ' m edicin es by d esig n ' indu st ry. Com panies such Drug abuse
as GlaxoSmithKline h ave team s of chemists and
bioch emists working alm ost around th e clock to Som e o f the very useful dru gs developed by chemists
discover, test, ch eck fo r safety and produ ce dru gs can be habit fo rming . For example, barbiturates (in
that can d eal with almost every known illness. sleeping tablets) and amph etamines (stimulants) fa ll
into thi s category. An o ther drug that h as created
T able 15 .4 shows the structures o f a selectio n problems in the past is Valium , which is no t itself
of som e o f the m o re comm on d ru gs available addicti ve but when u sed in the lo ng term m akes
at the present time, alo ng with their u ses . The people d ependent o n it. Severe p sych o logical and
commo n nam es for th ese d rugs arc used , since their physio logical p roblem s can arise.
system atic, th eoretical nam es arc extremely complex.
Checklist
It sh o uld be n oted , h owever, that it is the o piates Questions
which cau se addiction. Cocaine and heroin arc just
two examples o f such substances . Co nsequen ces 1 Using the data given in Table 15.4, suggest which of the
o f the addictio n include personal neglect , b oth o f
nutritio nal need s and o f hygien e. For a short-term pharmaceuticals contains:
feelin g o f wdl-bcing (' fi x'), the addict is prepared
to d o alm ost anything . Addi cts o ften turn to a a sulfur c an - NH2 group
life o f crime to fulfil their cravin gs fo r the o piates. b an -OH group d an ester group.
Addicts, especially th ose inj ecting dru gs, arc at a
hi gh risk o f HIV (human immuno defi ciency viru s) 2 Drug abuse is a rapi dly growing problem worldwide.
infection as they o ften share needles with o ther drug
addicts, who may be HIV positive. Public awareness Using the information given in this section as well as
campaigns aim to educate everyone on the dangers
in societ y, including dru g abu se and its related risks . your research skills, make a list of the addictive drugs.
(Figure 15 .28 )
Also explain the problems that drug abuse can cause.
L-
Checklist
f
After studying Chapter 15 you should know and understand
~ the following terms.
g • Aerobic respiration Respira tion that takes place in the
E presence of air.
. ,., • Alcohols Organic compounds containing the -OH group.
They have the general formula CnHzn+10H . Ethanol is by far
~ · ~".' .'• ~I the most important of the alcohols and is often just called
'alcohol '.
-.
• Amino acids These naturally occurring organic
Figure 15.28 Increasing public awareness of the risks associated with compounds possess both an -NH2 group and a -COOH
drugabuse isveryimportant . group on adjacent carbon atoms. There are 20 naturally
occurring amino acids, of which glycine is the simplest.
• Anaerobic respiration Re spiration that takes place in the
absence of air.
• Biopolymers Natural polymers such as starch and
proteins.
• Biotechnology Making use of micro-organisms in
industrial and commercial processes. For example, the
process of fermentation is brought about by the enzymes in
yeast.
• Biuret test The test for proteins. A mixture of dilute
sodium hydroxide and 1% copper(u) sulfate solution is
shaken with the material under test. A purple colour
appears after about three minutes if a protein is present.
• Carbohydrates A group of naturally occurring organic
compounds which can be represented by the general
formula(CH 20)_..
• Carboxylic acids A family of organic compounds
containing t he functional group -COOH . They have the
general formula CnHzn+iCOOH . The most important and
well known of these acids is ethanoic acid, which is the
main constituent in vinegar. Ethanoic acid is produced by the
oxidation of ethanol.
• Condensation polymer A polymer formed by a
condensation reaction (one in which water is given out). For
example, nylon is produced by the condensation reaction
between 1,6-diaminohexane and hexanedioic acid.
15 ORGANIC CHEMISTRY 2
• Di peptide Formed by the reaction of two amino acids. • Monosaccharides A group of simple carbohydrates.
• Disaccharide Two monosaccharides joined together, for They are sweet to taste and are water soluble (for example,
glucose).
example maltose.
• DNA Abbreviation for deoxyribonucleic acid. It belongs to • Pharmaceuticals These are chemicals called drugs that
are prepared and sold with the intention of treating disease
a group of biopolymers called the nucleic acids. It is involved (for example, methyldopa).
in the polymerisation of amino acids in a specific order to
form the particular protein required by a cell. • Polyamide A condensation polymer, such as nylon, that
• Drug Any substance, natural or synthetic, that alters the contains the amide link, -NHOC-.
way in which the body works.
• Drug abuse This term usually applies to the misuse • Polysaccharides A group of more complicated
of addictive drugs, which include barbiturates and carbohydrates. They generally do not form true solutions
amphetamines, as well as the opiates, cocaine and heroin. and do not have a sweet taste (for example, starch).
These drugs create severe psychological and physiological Proteins Polymers of amino acids formed by condensation
problems. This leads to a variety of personal problems for reactions. They fall broadly into two categories: fibrous
the user. proteins (for example, keratin and collagen) and globular
• Esters A family of organic compounds formed by the proteins (for example, casein and albumen).
reaction of an alcohol with a carboxylic acid in the presence Saponification A reaction in which an ester is heated
of concentrated H2S04. This type of reaction is known with an alkali, such as sodium hydroxide, producing a free
as esterification. Esters are characterised by a strong and alcohol and an acid.
pleasant smell (many occur in nature and account for the
smell of flowers). • Soapless detergents Soap-like molecules which do
• Fermentation A series of biochemical reactions brought not form a scum with hard water. These substances
about by the enzymes in yeast or, more generally, by micro- have been developed from petrochemicals. Their calcium
orgarnsms. and magnesium salts are water soluble and they are
Functional group The atom or group of atoms biodegradable .
responsible for the characteristic reactions of a compound.
• Genetic engineering The deliberate manipulation of the • Soaps Substances formed by saponification. In this
genes in anorgarnsm. reaction, the oil or fat (glyceryl ester) is hydrolysed by
• HIV Short for human immunodeficiency virus, from which aqueous sodium hydroxide to produce the sodium salt of
AIDS (acquired immunodeficiency syndrome) can develop. the fatty acid, particularly sodium stearate (from stearic
• Hydrolysis A chemical reaction involving the reaction of a acid). Soap will dissolve grease because of the dual
compound with water. Acid hydrolysis usually involves dilute nature of the soap molecule. It has a hydrophobic part
hydrochloric acid, and enzyme hydrolysis involves enzymes (the hydrocarbon chain) and a hydrophilic part (the ionic
such as amylase. head) and so will involve itself with both grease and water
molecules. However, it forms a scum with hard water by
reacting with the Ca2+ (or Mg2+) present.
Q Organic chemistry 2
• Additional questions I4 starch -+ monosaccharide AY~'.~t liquid B + ca rbon dioxide
hyd~ :~~or k hut-+
1 Explain the following.
a The problem of plastic waste has been overcome. potas,lum
b The majority ofdetergents produced today arc d l<hrom ateivd
biodegradable.
c In bread making, yeast is added to the mix and liquid C + water
the dough left to stand for a period of time.
d Poly(cthcnc) is a thermoplastic. ]=··--
2 a A detergent molecule may be represented by the liquid D + water
following simplified diagram.
ionic
head
covalent hydrocarbon tail a Name and give the formula and one use of each
of the substan ces A to D.
Use this representation ofa detergent molecule
in a series oflabdkd diagrams to show how b Write word and balanced chemical equations for
detergents can remove grease from a piece of the reactions involved in the formation of liquids
greasy cloth. B, C and D.
b Explain why detergents do not form a scum with
hard water, whereas soaps do. c Starch is classified as a natural polymer or
c The modern detergents arc biodegradable. 'biopolymer' Explain the meaning of this
(i) Explain what this statement means. statement.
(ii) Why is it necessary for detergents t o be
d Name the processes by which:
biodegradable? (i) starch is broken down
(ii) liquid Bis formed
3 A piece of cheese contains protein. Proteins arc (iii)liquid C is formed
natural polymers made up ofamino acids. There (iv) liquid Dis formed.
arc 20 naturally occurring amino acids. The
structures of two amino acids arc shown below. 5 a Copy the following table and complete it by
writing the structural formulae for methanol and
mcthanoic acid.
Methane Methanol Methanoicacid
glycine alan in e H
H H H-CI -H
I I I
H2N -1-cooH H2N-1-cooH H
H CH, b Describe a simple chemical test that could be
used to distinguish methanol from methanoic
a Name the type of polymerisation involved in acid.
protein formation.
c (i) Name the class of compound produced
b Draw a structural formula to represent the part when methanol reacts with methanoic acid.
of the protein chain formed by the reaction
between the amino acids shown above. (ii) Name the type of reaction taking place.
(iii) Write a word and balanced chemical
c What is the name given to the common linkage
present in protein molecules? equation for this reaction.
(iv) Give two uses related to the class of
d Why is there such a huge variety of proteins?
e Name and describe the features of the two broad compound formed in this reaction.
groups of proteins.
15 ORGANIC CHEMISTRY 2
d The foll owing reactio n takes place when 8 a Name the polym erisatio n process that is used to
methan o l is burned: make both nylo n and Terylen e.
2CH,OH(I) + 302(g) - 2C0 2(g) + 4H20 (g) b Name the starting materials fo r making:
11H= - 1452kJmol- 1 (i) nylon
(ii) Ter ylcne.
(i) H ow much heat energy would be liberated
by burning: c Give the name and formula o f the small
0.5 1110! o f methano l? m o lecule prod uced during the po lymerisatio n
4.0mo l o f m ethano l? reactio ns to produ ce bo th n ylo n and T erylcne.
4 g o f methano l?
d Give the name o f the ch emical link that ho lds
(ii) Calculate th e volume o f carbo n dioxide t o g et h e r:
produced at room temperature and pressure (i) nylon
(rtp ) when 16 g of methanol arc burned. (ii) Ter ylcne.
(A.: H = l ; C = 12; 0 = 16 . On e mole o f
any gas at rtp occupi es 24 dm3 . ) e Give two uses fo r:
(i) nylon
6 Why is it safe fo r us to use vinegar, which contains (ii) Ter ylcne.
cthan o ic acid , o n food while it would be extremely
dangerou s fo r u s to u se dilute nitric acid fo r th e f Explain th e difference between the type o f
sam e purpose? polymerisatio n you have n am ed in pa.rt a and
additio n po lym erisatio n.
7 a Which carbo xylic acids and alco ho ls would you
use to m ake the fo ll owing esters? 9 What arc the advantages and disad vantages o f th e
(i) butyl mcthanoatc two m ethods used to manufacture eth an o l:
(ii) ethyl mcthanoatc a by tCrmentatio n
(iii)propyl propano atc b by the hydratio n o f ethenc with steam ?
b W hich esters would be mad e using the fo llowing
c1rboxylic acids and alco h o ls?
(i) ethano ic acid and butan-1- o l
(ii) methan o ic acid and m ethanol
(iii)propano ic acid and butan-1- ol
c Draw the structures o f the foll owing esters:
(i) ethyl mcthan oate
(ii) propyl ethano ate.
d Give two u ses related to the class o f compound
fo rmed in this reactio n.
@ Experimental chemistry
Objectives for experimental skills and investigations Notes on qualitative analysis
Appearance or smell
Suggestions for practical work and assessment
Safety Flame colours
Red ox Tests for aqueous cations
Tests for aqueous anions
Tests for gases
• Objectives for Safety
experimental skills and
investigations In the suggested practi cal exercises, mate rials arc
u sed w hich , altho ug h famili ar in many cases, arc o f
The IG CS E c he mi stry syllabu s suggest s that stude nts a potentiall y hazardo us nature, and appro priate care
sho uld be able to : and precautio n s sh o uld be taken. We believe that
the exp erimen ts can be carried out safely in school
1 kn ow h ow t o safely u se tcchniqm:s, apparatus laborato ries. H owever, it is th e respo nsibility o f th e
and ma te rials ( including fo llowing a seque nce o f t each er t o make the final d ecision d ep ending o n th e
instruc tio ns w he re appropriate) circumstan ces at the tim e. G oggles sh ould b e worn at
all times . In certain cases disposable gloves and fum e
2 plan expe rime nts a nd investig ation s cupbo ard s will be required.
3 make and record ob ser vatio ns, measure m ents and
Teach e rs must e nsure that they foll ow th e safety
estimates guidelines set d own by their e mployers, and a risk
4 interpret and evaluate experimental o bservatio ns assessm ent must be completed for any experiment
that is carried o ut. Teachers sho uld draw students'
and data atte ntio n t o the hazard s involved in the pa rticular
5 evaluate m eth ods and suggest possible exercise t o be performed.
improvem ents. Red ox
All candidates must take a practical pape r based o n The concept o f red ox, either in its ele m entary form
the criteria above. Yo u must take o ne o f the fo ll owing ( that is, as the loss or gain o f oxygen ) o r as electron
pape rs: transfer, is a con stant the m e th roug ho ut the syllabu s
and the associated practical work. The list su ggest s
• Pape r 5 - Practical Test , or plenty o f varied examples, designated by R, to
• Pape r 6 - Alte rnative t o Prac tical (written paper ). reinfo rce the theor y.
So me examples o f exam style qu estio ns fr o m Pape r 6 Chapter 1 The particulate nature of
arc given o n pp . 26 4-74. The practical assessment is matter
20% o f the available marks.
Solids, liquids and gases
• Suggestions for practical
work and assessment • A simple d e m o nstratio n t o illu strate the three states
o f matte r and their intc rconvcrsio ns - ice, w ater
The foll owing list su ggest s practical exercises that and steam.
could be used to both support the assessment
o bjectives given above and e nrich the study o f • Dem o nstrate the compressibility o f gases and th e
chemistry; in addition, it sho uld suggest plenty o f inco mpressibility of liquids by u sin g a syringe t o
o pportunities fo r the enhancem ent and assessm ent sh ow that the volume of a gas (e .g . air) d ecreases
o f practical skills. The list is neithe r exhau stive nor with pressure w he reas that o f a liquid (e .g. w ate r )
prescriptive: the actual selectio n o f practical work, docs not.
whe th er from this list or fro m elsewhere, has to be
governed by local fact ors such as the facilities available,
safe ty consideratio ns and the ability o f the class.
16 EXPERIMENTAL CHEMISTRY
Changes of state Diffusion
• Brownian m o tio n can be d em on strated using
• Measure the m eltin g points o f bo th a pure
sample and an impure sample o f a solid ; this will po llen or sm o ke . Sm oke cells arc commercially
d em o nstrate that m elting po int is a m eans o f ava ilable.
assessing purity. • Illustrate gaseous diffu sion u sin g a gas jar o f
• M easure th e temperature o f melting ice, then b romin e va pour and a gas jar o f air as described in
repeat after adding salt to the ice. the text ( Fig ure 1.13, p. 6).
• M easure th e melting po int o f octad ecan o ic acid • An additio nal d em o nstratio n o f gaseous diffusio n
u sing a water bath ( Fi gure 1.12, p. 6 ), th en is similar, but uses a gas jar of hyd rogen above a gas
repeat using a sample that is contaminated with a jar of carbon dioxide. Both gas jars can Ix tested for
trace o f salo l (phenyl 2-hyd roxyb cn zoatc ). th e presence of carbon dioxide. It is preferable to
• Use a liquid paraffin bath o r d cctrical heating set up this experiment twice, then , using the second
apparatus to measure the melting point of an set, h yd rogen can b e shown to b e in both jars.
unknown compo und and decide whether it is a • D em o nstrate the ammo nia and hydrochloric acid
pure sample. experiment d escribed in the text (Figure 1.14, p . 7 ).
This also illu strates the dependence of the rate o f
• Bo iling point as a criterio n o f purity. U se a test- diffusio n on the relative molecular mass of a gas, Mr.
tu be and therm o meter to measure the bo iling • An alternative is an arrangement o f mano m eter
point o f a suitable liquid. A simple example would and porous pot which effectively compares th e rate
in volve heatin g calcium chlo ride solutio n in a test- of diffusio n o f a gas with that o f air (Figure 16. l ).
tube with a few anti-bumping g ranules. N o te that This can be u sed to show that carbon di oxide
th e bulb o f the therm om eter must Ix in the liquid diffi.1ses slower than air and hyd rogen diffuses faster.
itself to measure its bo iling po int (typically 102 °C
in this case ) and no t in the vapo ur above the liquid b eake r
(wh ere it would register 100°C).
co lo ured
• The fractio nal distillation o f a mixture o f water and
ethano l ( Fig ure 2 .22 , p. 2 1) illustrates that a pure a The pressure inside the porou s pot rises because hydrogen diffuses in
liquid boils at on e temperature but a mixture o f fasterthanair diffusesout.
liquids b oils over a range o f tem peratures.
carbo n dioxid e
• A liquid will b oil at a lower temperature wh en the gas -+
external pressure is reduced , e .g. by using a water
pump . The variati on o f bo iling po int with external
pressure can be d em on strated with a volatile liquid ,
such as m ethan ol; it is advisable to introdu ce
som e fo rm o f cold trap to redu ce the am o unt o f
vapo ur entering the waste. An alternative is to allow
bo iling water to cool and so sto p b oiling, and then
redu ce th e pressure: it will start to bo il again at a
temperature below 100 °C
• Io dine, ammo nium chloride or dry ice can Ix
used to demo nstrate sublimatio n. H eat the solid
ammo nium chloride or iodine in a test-tube to show
that it disappears fro m the bottom o f the tu be and
condenses higher up the tube, where it is cooler.
Heating and cooling curves po ro us
po t
• Studen ts will already Ix familiar with melting and b The pressure inside the porous pot falls because air diffuses out faster
bo iling, so a m ore profitable approach mig ht be to thancarbondioxidediffusesin.
supply th em with data to con stru ct and interpret
th ese curves. Figure 16.1 Comparing the rate of diffusion of gases with that of air.
Suggestions for practical work and assessment
• Diffusion o f a co lo ured solute in water. A large • lllustratc the use of chromatography as a test of
crystal of copper(11 ) sulfate is added to a measuring purity and an analytical tool. Suitable examples
cylinder o f water and is o bserved over several days. include colo ured inks, food colo uring, pigments
fro m fl owers or grass, metallic catio ns and
Chapter 2 Elements, compounds and id entificatio n of sugars. At least o ne exercise sho uld
experimental techniques involve d eveloping a ch romatogram and at least
on e sh o uld in volve the measurement o f Rr valu es.
Elements
Gels, sols, foams and emulsions
• Display samples of as many elements as possible, • Set up a circus of gels, sols, emulsio ns and foa ms, e .g.
either on information cards or on a copy of the
Peri odic Table. Thi s is an effective o bservati on 'jelly', milk, pumice sto ne, polyurethane foa m , bread ,
e x er cise. emul sion paint, cola , hair cream, aerosol dispenser,
salad cream. A silica gel can be made fro m sodium
• Set up a circus o f activities which includes both silicate and hydrochloric acid. C lassify the examples
collecting data fr om computers or data books according to type of colloidal system.
(e.g. melting and b o iling points and d ensity) • Make a coll oidal sol o fi ron( m ) hydrox id e by
and practical exercises o n comparing electrical adding aqueous iron(m ) chlorid e to boiling water,
condu ctiviti es. These activities will illu strate the o r a coll o idal sulfur sol by adding dilute aqueous
physical differences between m etals and no n-metals. sodium thi osulfate to hydrochloric acid. For both
o f these sols, it can be sh own that th e solid phase is
Compounds and mixtures no t separated by filtrati o n.
• D em o nstrate the combinati o n o f elem ents to form Chapter 3 Atomic structure and
compound s, fo r example magn esium and oxygen , bonding
iron and chlo rine, hyd rogen and oxygen, zinc and
sulfur, carbo n and oxygen , and aluminium and Ionic bonding
iodine.
• Look up the melting and boiling points of io nic
• D em o nstrate the iron and sulfur experiment compounds in data books.
d escribed in the tex t (p. 16).
• Show that most io nic compo und s dissolve in water.
Separating mixtures • Dem o nstrate that an io nic compo und , po tassium
• Filtratio n, d ecanting and centrifu g ing to separate a iodide or lithium chl oride , condu cts electricity in
solid fr o m a liquid (p. 18). the m o lten state but n ot as a solid.
• Evapo ratio n to obtain a solute fro m a solutio n Covalent bonding
(p. 19).
• Look up the meltin g and boiling points of simple
• Crystallisation o f impure bcnzoic acid. Bt:nzoic covalent compo unds in data books.
acid is contamin ated with a trace o f a blue dye
and then dissolved in the minimum amount o f • Show that they arc no t good co ndu cto rs of
boiling water. Allow to coo l and separate crystals electricity in the liquid phase - dem o nstrate this
by filtrati o n. The blue colour will have disappeared with hexane, ethano l o r phospho ru s trichl oridc.
or become fainter, showing that crystalli satio n h as
rem oved the impurity. • Show that graphite is both soft: and a good
conductor o f electricity.
• Simple distillation to separate a solvent fr om a
solutio n (p. 20 ). • Use a glass cutter to illustrate the hardn ess o f
diamond.
• Separatio n o f immiscibl e liquids using a separating
fi.mncl (p. 20). Glasses and ceramics
• Heat a piece o f glass tubing to demonstrate that it
• Fracti onal distillatio n o f a mixture of ethano l
and water will separate two miscible liquids and gradually softens, will bend and can be pulled into
illustrates that an impure liquid d ocs no t boil a fin er tube. These changes sh ow that g lass is a
at a specific temperature but over a range o f supercooled liquid , n o t a solid.
temperatures (p. 21 ).
16 EXPERIMENTAL CHEMISTRY
Metallic bonding that in Figure 5 .2 (p . 7 2 ), but with an ammeter
in preference to the lamp, and m easure the
• Tht: propcrtit:s o f typi cal metals will bt: covered condu ctivity o f a selectio n o f liquids, fo r example
by the practical work on the transitio n dcmcnts in sodium chlo ride solutio n, hyd rochloric acid,
Chapter 9. sodium hyd roxid e solution , water, dilute ethan o ic
acid , aqueou s ammo nia , paraffin and ethan o l.
Chapter 4 Stoichiometry - chemical • Elect rolysis as d ecom positio n , for example of
calculations copper chlorid e soluti o n , zinc b romid e so lutio n ,
hyd rochloric acid and acidified water. Include tests
Moles and gases fo r chlorin e, o xygen and hyd rogen. R
• Elect rolysis o f aqueou s solution s o f th e followin g
• M easure the m o lar volum e at rtp fo r hydrogen. usin g inert electrodes : sodium chlorid e, copper(11 )
U se a fla sk with a delivery tube and coll ect the sulfate, sodium sulfate and sodium hydroxid e.
gas over water in an inverted m easuring cylinder • Elect rolysis o f aqueou s copper(11 ) sulfatc u sing
o r burcttc (Figure 16.2 ). Put an excess o f dilute copper electrod es .
hydrochlo ri c acid, say 100 cm3 of2m o l dm-3 acid , • Examples o f elect roplating, such as nickel plating .
in th e fla sk and add a piece o f magn esium ribbon U se a nickel ano d e, a copper cathode and nickel
wh ose mass is kn own accurately and is abo ut 0.1 g . sulfatc solutio n as the elect rolyte in a cell similar to
(It is useful to measure the mass o f a 1 m leng th o f that in Figure 5 .20 (p. 84).
ribbo n and then th e mass o fa small er length can
be calculated. ) M easure the volume o f hyd rogen Chapter 6 Chemical energetics
collected in the m easuring cylinder or burcttc.
• Simple distillatio n o f a synthetically manufactured
lift the cork slightly hydrogen 'crude o il' o btain ed fr om chemical suppliers.
collects
rgoe,;,mand immediately replace; here • Insp ectio n o f some o f the fra ctio n s o f the primary
falls ;o,o ,c;d distillatio n o f crude o il - colo ur, viscosity, bo iling
po int and flammability.
cotton thread
magnesium • Show examples of exothermic and endothermic
ribbon reactio ns.
• Dissolve ammo nium nitrate in water - an
excess dilute example o fan e nd o thermic change.
hydrochloric • Di ssolve anhyd rous copper(11 ) sulfatc in water -
acid an example of an exothermic change.
Figure 16.2 Measuring the molar volume of a gas at rip.
• D etermination o f the enthalpy o f combustio n o f
• M easure the m o lar volum e at rtp fo r carbon ethano l, as d escribed in questio n 6 o n p. 102.
dioxide. Repeat the experiment above, u sin g a
kn own mass o f a carbo nate and coll ecting the • Sh ow that the reactio n between zinc and coppcr(n )
carbon dioxid e in a syringe. io n s is exo thermic.
• Add zinc du st to copper(11 ) sulfatc so lutio n. N o te
Chapter 5 Electricity and chemistry the temperature of the solution before and after
the additio n o f the zin c. H ere ch emical energy is
• Intro ducto ry practical. Elect ro lytes o nly condu ct transformed into heat energy.
in th e liquid phase, either mo lten or in aqueou s • Set up a zin c/copper cell and n ote its po larity
solution. Exp eriments can be carried out to and vo ltage ( Fig ure 6.23 , p . 98 ). Here ch emical
illu strate th e differe nces between st ron g, weak energy is chan ged into electrical en ergy. Repeat
and no n-electrolytes. U se a circuit similar to using o ther cell s, fo r example C u/ Ag, Fe/Cu
and M g/Cu. This will dem o n strate that the
reactivity series can b e established u sing cells. R
• T o simulate a foci cell, electrolyse water fo r a few
minutes until both electrodes arc covered with
bubbles o f gas. Replace the power supply with a
voltmeter. This will sh ow that th e cell produ ces a
Suggestions for practical work and assessment
voltage when the hydrogen o n o ne electro de reacts • Decompositio n o f sodium chloratc(r), catalysed by
with the oxygen o n the o ther by the t r.i.nsfcr o f a cobalt( n ) salt.
electrons through the external circuit. R
2N,CIO(,q) - 2N,Cl(,q ) + 0 2(g)
Ch apt e r 7 Ch em ica l react io ns
U se the sam e apparatus as in the previo us exercise
• Reaction o f calcium carbo nate and acid to obtain data o n the volume o f oxygen evolved
(Fig ure 7.3, p. 105 ) - the effect o f con centrati on against time. This can be analysed to investigate the
and surface area. eftCct o f concentratio n o n the reactio n rate and o n
the volume of product.
• Reacti on o f sodium thiosulfate and acid
(Fig ure 7 .8, p. 107) - the effect o f con centration. • Identical mixtures o f sodium thiosulfate solutio n
and hyd rochloric acid arc used at different
• D ecompositio n o f hyd rogen peroxide, catalysed b y temperatures in the experim ent d escribed o n
mangancsc(I\-' ) oxid e - th e effect o f concentratio n p. 107 . Th e results illu strate how rate d ep end s
and mass o f catalyst o n the rate and o n the volume on tempcr.i.turc when the concentratio ns arc kept
of product. c on st an t .
First use a mixture o f 2cm 3 o f 2 0 vol hyd rogen • Compare a silver halid e that has bee n ex posed
peroxid e and 4 8cm 3 o f water, with 0 .2 g o f to lig ht with a sample kept in the dark. Prepare a
mangancsc(I\-') oxid e. Then use a mixture o f 4 cm 3 suspensio n o f silver bromide and divide it into two
o f20 ,,o l hyd rogen peroxide and 4 6cm 3 o f water po rtio ns. Wrap on e po rtio n in aluminium fo il and
with 0.2 g o f m anganese di oxid e. Finally use a ho ld the o ther near a brig ht lig ht.
mixture o f2 cm 3 o f2 0vol hyd rogen peroxide and
48 cm 3 o f water with 0.4 g of man ganese dioxide. • Divid e a mixture o f b romine and hexan e into two
Collect th e oxygen over water in an in verted po rtio ns. Expose o ne to brig ht lig ht while the
measurin g cylinder o r burette and o btain sets o f oth er is kept in th e dark. O nly the sample exposed
readin gs o f volume against time. to the lig ht will evolve h yd rogen b romid e, and its
brown colour will fad e.
• Add a 2 cm leng th o f mag nesium ribbon to an
excess o f2m ol dm-3 hyd rochloric acid and m easure • Biology-type ex perimen ts on g reen leaves and
the time taken fo r the metal to react . Repeat, with lig ht. It is p robable that th e stud ents will already be
the same sized piece o f magn esium but a different famili ar with these.
concentration o fa cid. (An other \'crsio n o f this
experim ent is to make tcmper.i.turc the variable and • Th e cftCct o f enzymes on th e d ecompositio n o f
use h ydrochloric acid at different temperatures.) hyd rogen peroxid e. Add a pi ece o f raw liver to
20 vol h yd rogen peroxide.
• Add a 2 cm leng th o f mag nesium ribbon to an
excess o f2 m ol dm -3 ethan oic acid. Measure the • Add a few d rops o f washing -up liquid to 20 vol
time taken for the metal to react and compare thi s hyd rogen peroxid e. Di vide this mixture into t wo
result with th e on e ab ove . po rtio ns and add m anganese(1v) o xide to o ne
portio n. Compare th e rate o f d ecompositio n o f
• Reaction o f m etal and acid - the effect o f hyd rogen peroxid e in the two samples.
con centration and surface area o n the reaction r.i.tc
and o n the volume o f produ ct. Ch apte r 8 Acid s, bases a nd sa lts
Collect the hyd rogen and o btain data o n the Acids a nd a lka li s
volume evolved against time. The appar.i.tus used
could be a fl ask with delivery tube and a gas syringe • With simple indicators, find the acid colour, the
or burcttc. A leng th o f magnesium ribbo n is alkaline colo ur and the neutral colo ur. H o ld the acid
suspend ed above excess acid and is all owed to fall tu be and the alkaline tube up to a light together and
into the acid as the timing starts. look throu gh both to see the neutr.i.l colour.
Th e experim ent could be repeated using different • Diluti o n experiments using universal indicator
leng ths o f ribbon and diffe rent concentratio ns o f and 0.1 m o l dm-3 solutio ns o f hyd rochlo ric acid ,
acid. Also, a mass o f magn esium powd er equal to sodium hyd roxid e, cthan oic acid and amm onia.
that of the ribbon could be suspend ed above the Th ese will esta blish the pH scale and prom o te an
acid in a sm all tube. und erstanding o f the distinctio n between stro n g
and weak elect rolytes.
16 EXPERIMENTAL CHEMISTRY
• D em o nstrate that a solution o f h ydrogen chlorid e • By titration find th e mass o f o ne m o le o f an
in dry h exan e d oes no t exhibit acid properties. It acid, H 2 Y, g iven a solutio n o fH 2Y of kn own
d ocs n ot conduct ckctricity, n or d oes it react with concentration in gdm-3. A suitable acid would
mag nesium. be cthancdioic acid, with pheno lphthalein as the
indi cator.
Formation of salts
Chapter 9 The Periodic Table
• Reactio n s o f a typical acid with metals. Use
hydrochlo ri c and/or sulfori c acid with mag nesium , Group I -the alkali metals
aluminium , zinc, iron and copper. R
• Teach ers can demo n strate that lithium , sodium and
• Reactio n s o f t ypical acids with bases and potassium arc soft metals and good condu ctors o f
carbonates. Use a sckctio n of alkalis, insoluble electricity, and students can find the densities and
bases and carbonates with hydrochlo ric, sulfuric melting po ints o f these metals usin g data books.
and nitric acids.
• The metals arc burnt in air o r oxygen and then
• Small-scak preparatio n o f a salt fr o m a m etal - it is sh own that their oxid es arc alkaline. Using a
mag nesium sulfatc -7 -watcr (p. 123 ). d cfla gratin g spoon , the h ot m etal is placed into
a gas jar o f oxygen , the colo ur o f the flam e is
• Preparatio n o f a salt by titratio n - sodium chl oride no ted and the pH o f the white powder fo rmed is
or sod ium sulfatc -1 0 -watcr (p. 124). measured.
• Preparatio n of a salt fro m an insoluble carbo nate • The reactions of lithium , sodium and potassium
and an acid - nickel sulfatc-7 -watcr (p. 123). with cold water can be demo n strated to sh ow that
alkaline so lutio n s arc formed and to illu strate the
• Preparatio n of a salt fro m an acid and an insoluble difference in th eir rcactivitics.
base - coppcr( n ) sulfatc -5-watcr (p. 124).
• Sodium is burnt in chlorine to dem o nstrate the
• Tests for anions - nitrate, chl o ride, bromide, fo rmatio n o f sodium chlorid e.
io did e, carbo nate and sulfatc (p. 262 ).
Group II -the alkaline earth metals
• Preparatio n ofa number o f insoluble salts by
precipitation on a test-tube scale - an exercise in • Similar exercises as fo r Group I can be conducted
practical skills, observatio n, recordin g and writing with mag nesium and calcium. In addition, it can be
eq uatio ns. demonstrated that magn esium reacts slowly with
cold water but will burn in steam ( Fig ure 10.3,
• One fo rmal preparation o f an insoluble salt, such as p. 151 ).
lead iodid e, to include filtering, washing and drying
(p. 125). Group VII -the halogens
Crystal hydrates • Investigate their physical properties by inspectio n
and u sin g data books.
• Thermal decomposition o f a hydrated salt -
coppcr(n ) sulfatc-5 -watcr. Add water carefull y to • D em on strate their displacement reactio n s. R
th e anhydrous salt ( Fig ure 8.21, p. 128). Add chlorin e water to p o tassium bromide solutio n.
Add chlo rin e water to po tassium iodide soluti on.
• Find x in M gS04 .xH 2 0 or BaC12 .xH20 by thermal Add bromine water to potassium iodide solutio n.
d ecompositio n. Weigh a clean, dry crucible and
lid. Add between 2 g and 3 g o f the h ydrated • D em on strate the fo rmation of halides . Use small
co mpo und and re-weigh, then heat to constant quantities in all o f these reactio n s, which must be
mass. From th e results calculate x. performed in an efficient fi.un c cupboard.
• H eat aluminium turnings in a current o f chlo rine
Titration or add ho t aluminium powder to a gas jar of
chlorine . Add ho t aluminium powder to bromine
• By titratio n find the con centration o f a solutio n o f vapour. Add o ne drop of water to an intimate
an alkali u sing a standard acid, hyd rochloric acid, as mixture o f aluminium powd er and iodin e.
d escribed in the text (p. 129). • Reactio n o f copper ( use Dutch metal ) and
chl orine .
• Using the sam e method ( but a different
calculation ), find the con ce ntratio n ofa solutio n of
an alkali u sing sulfuric acid.
Suggestions for practical work and assessment
• Reactio n o f ph osph o rus and chlorine. Put a small to the aqu eous nitrate o f ano ther m etal. The
pico.: o f white phospho rus o n a spoo n into a g as stud ents look fo r evid ence o f displacem ent and so
jar o f chlorin e . establish an order o f reactivity. Suitable m etals arc
magn esium , zinc, lead , copper and silver. R
• H yd rogen and chlorine . Make a mi xture o f these
gases by elect rolysis and expose it to a bri ght Identifyi ng met al ions
light fro m a pho tographic fla sh or burnin g
magnesium. • Reactions o f catio ns in aqueous solutio n with
sodium h yd roxid e - Al3+ Fe1+ Fc3+ C ul+ Cal+
Met a ls Zn 1 , C r3+,. A,; excess o f ;odim~ hyd,roxid ; solutio n
is added slowly to a small volume o f the solution
• Most metals react with dilute acids. Add a small containing the cation. This is an exercise in
piece o f a metal to dilute h ydrochloric acid and test o bservatio n, organisatio nal and recording skills and
fo r hyd rogen. U se magn esium , aluminium , zinc, in the ability to write chemi cal equati ons - word ,
iron and copper. m o lecular and io nic.
• Differences in the physical p roperties o f the • Reactions o f the sam e catio ns with aqu eo us
transitio n elements, such as melting points and ammo nia. This is essentially a repeat o f the exercise
d ensities , can be establish ed fr om data books. above but with less emphasis o n equation writing.
• Transitio n m etals react with o xygen to fo rm • Identificatio n o f unknown catio ns using sodium
inso luble oxides that arc no t alkaline . Th e reactio ns hyd roxid e solutio n and aqueous ammo nia.
o f these metals with acid s will illustrate their lower
reacti vity. Amp hot eric hyd roxides and oxides
• An o bservatio nal exercise usin g compound s o f • H yd roxides arc classified as basic o r amphotcric .
chro mium , man gan ese, cobalt, nickel and copper Th e qualitative exercises above will p rovid e a
will emphasise that these m etals have colo ured practi cal basis fo r th e und erpinning th eory. A useful
compound s. extensio n exercise is to provide unkn own catio ns
in solutio n and fo r the students to ascertain if their
• Flam e colo urs (p. 2 6 1). hyd roxid es arc basic or amph o teri c.
Ch apt e r 10 Meta ls • Ano ther in fo rmative practical involves adding
dilute acid d ropwise to an aluminatc or zincatc and
Typica l reacti ons of m eta ls o bserving th e changes in reverse.
• Reaction o f m etals with dilute acids (p. 150). R AJ3+ 0C~:- Al(OH ) 0C~:- Al(OH ) -
• Reaction o f metals with air and oxygen ( p. 151 ). R
• Reaction o f metals with cold water o r steam 3 4
(p. 151 ).R • O xid es arc classified as basic, acidic, neutral or
amph o tcri c. An exercise with unkn own oxides is
Competit ion reactions conducted using the fo ll owing tests:
• Docs the ox id e dissolve in water 1 lf so, m easure
• Redu ctio n o f m etal oxides by o ther m etals the pH.
(Fig ure 10.6, p. 154). D em o nstrate th e Th crmit • Do the insoluble o xid es react with 4 m o l dm -3
reactio n and the reactio ns between the m etals nitri c acid 1
mag nesium , zinc, iro n and copper and their oxides. • D o the insoluble o xides react with 4 m ol dm -3
Thi s will establish an order o f reactivity for these sodium hyd roxide?
metals. Some o f these reactio ns arc very vio lent so
the use o f small quantities and a reh earsal before Act ion of heat on met al compou nds
the class d em onstratio n arc essential. R
• Acti o n o f heat on metal o xides .
• Redu ctio n o f m etal oxides by methane/hyd rogen . • Actio n o f heat on hyd roxides . It is easier to use
It is safer to use m ethane, which is passed over
heated copper oxide. R m etal hyd roxid es that have a different colo ur fr om
• Metal/ metal displacement reacti ons in aqu eous
solutio n. C lean pieces o f a m etal arc add ed
16 EXPERIMENTAL CHEMISTRY
th eir oxides, such as the hydroxides o f iron , kad additio n o f dilute nitric acid the h yd roxide will
and copper. reappear, only to dissolve with th e additi on o f mo re
• Actio n o f heat o n nitrates. For safety reason s this nitric acid.
is best d em on strated as the re arc som e seri o us
hazards - mo lten p otassium and sodium nitrates/ OH- OH-
nitrite, dccrcpitatio n with kad nitrate and th e metallic cation W metal hydroxide W metallic anion
emissio n o f the poison ou s gas, nitrogen di oxid e.
• Actio n o f heat o n carbo nates - sec p. 152 . Equilibria
Rusting of iron • k c/water and o ther chan ges o f state.
• Saturated so lutio ns in equilibrium with excess
• E xpe rime nt o n ru sting as d escribed in the t ext
(Figure 10.20 , p. 162). R solute.
• Bismuth chlo ride and water. Prepare a solutio n o f
• Set up a cell with two iron elect rod es conn ect ed
th rough a voltmeter and bubble oxygen onto one bismuth chloride in the minimum o f h yd rochloric
elect rod e. From the po larity o f the cell, stud ents acid and add to a large excess o f water.
can d educe the directio n o f the elect ron fl ow
and an alyse the cell reaction s in terms o f electron Bi C13 + H 20 ;:= BiOC l(s) + 2H C 1
transfer. R
white
• Set up a zinc/iron cell to d em o n strate sacrificial
protection . An alyse the cdl reacti on s as above. R On the additio n o f hydrochloric acid, the white
precipitate will become fainter and then disappear.
Chapter 11 Air and water The additio n o f sodium h yd roxide solutio n will
cause the precipitate to reappear. This illustrates
Air different p ositio n s o f the sam c cqu.ilibrium .
• Iodine will react with chlorine to fo rm iodine
• Find th e percentage o f oxygen in th e air as m on ochlo rid c, and with an excess of chlorine th e
d escribed in the text (Figure 11.6, p . 174 ). fo ll owing equilibrium will be establi shed.
Ammonia gas Cl2 + !Cl(!) cc IC13( , )
• Laborato ry preparatio n o f ammo nia ( Fig ure 11 .16, brown yell o w
p. 179 ).
The rem oval o f chlo rine b y blowing air throu gh th e
• The fo untain flask exp eriment ( Fig ure 11.18, U-tube or by inverting it resul ts in the fo rmatio n
p. 180). o f th e brown liquid, while the additio n o f chlorine
results in th e formatio n o f the yellow solid.
• Sh ow th at ammo nia is a base. N eutralise acid s by
adding 2 mol dm-3 aqueous ammonia to dilute • Fe3+(aq) + Ag(s) ;::! Fc2+(aq ) + Ag+(aq )
acids in the presence o f universal indicator. • FcCl3 + 3 KC NS cc Fc(C NS), + 3 KCI
• Sh ow th at ammo nia is a weak base. M easure the Altho u gh this eqmtio n is n o t strictly correct , at this
pH o fO . l m ol dm-3 aqu eous ammo nia and its level it is preferable to the io ni c equati on involving
condu ctivity. Compare the pH and conductivity FeCN S2+.
with those o fO.l mo l dm-3 sodium hyd roxide.
Alterin g th e temperature using ice -water o r ho t
• Precipitatio n o f m etal hyd roxides - sec C hapter 10. watcr will change the positio n o f cquilibrium
• Test fo r th e amm o nium io n (p . 262 ). and illu strate its d ep end en ce o n the exothermic
o r end oth ermic nature of th e reactio n. Similarly,
Reversible reactions changin g th e pressure by compressing a sample o f
the equilibrium mi xture in a gas syringe will also
• Acid/ base indicators . m ove the positio n of equilibrium.
• Actio n o f heat o n copper(n ) sulfatc-5-watcr.
• Add sodium h yd roxid e solutio n to a solutio n o f a • NH 4C l ;:= NH 3 + H C l
zinc, an aluminium or a lead salt. Th e hyd roxide H eat amm o nium chlo rid e to show the influen ce o f
will precipitate and then dissolve in excess alkali to tempcraturc o n the positio n o f equilibrium.
fo rm an aluminatc, zincate o r plumbatc. On the
Suggestions for practical work and assessment
Water • Preparatio n o f sodium sulfate-10-water by titratio n.
Use the sam e metho d as o n p. 124, using dilute
• Tests to show the presence o f water ll sing cobalt sulfuric acid and dilute aqueous sodium hydroxide.
chloride paper and anhydrous copper( n ) sulfate.
• Preparatio n o f sodium hydrogensulfate by titratio n.
• Tests to show that water is pure: it melts at 0 °C o r Use the resul ts fro m th e previous exercise but add
boils at l 00 °C. do uble th e titre o f acid to the sam e volllme o f
alkali.
Hardness in water
• Comparison o f the salts sodium sulfate and sodillm
• Standard experiments with permanently and hydrogensulfate . Compare their crystal shapes .
temporarily hard water. Measure the number o f Measure the pH of their aqueous solutio ns. Add
drops o f soap solutio n need ed to fo rm a permanent magn esium powder to both salts in solutio n. Add
lather in 10 cm 3 samples o f both types of hard water. excess dilute hyd rochloric acid and barillm chloride
Bo il both types and allow to cool. Then measure the solutio n to both soluti o ns.
number of d rops of soap solutio n needed to produ ce
a perm anent lather in 10cm3 samples o f the treated Concentrated sulfuric acid
samples of hard water. The study can be extended • Reacti ons with copper(11 ) sulfate-5-water and sugar.
to include the addition of sodium carbonate and • Oxidation of metals, such as copper.
treatment with ion exchange resins. • Make nitric acid and sulfuric acid.
• Compare soap and soapkss d etergents. Add soap Chapter 13 Inorganic carbon
solutio n dropwise with sluicing to samples of hard chemistry
and soft water. Repeat usin g a soapless d etergent.
Chapter 12 Sulfur Carbonates
Sulfur and sulfur compounds • Heat a piece o f calcium carbonate. Allow it to
cool and carefull y add water dropwise. Then add
• Burn sulfur in air or oxygen. Show that an acidic excess water and filter. Keep th e filtrate, a solutio n
gas is formed. of calcium hydrox ide. Make carbo n dioxide by
adding an acid to calcium carbo nate. Bubble
• Fo rmation o f m etal sulfides . Dem o nstrate tl1e this gas th roug h the previo llsly prepared calcium
reactio ns o f sulfur with iron, zin c and magn esium - hyd roxide solutio n until no furth er change is
care is needed. observed. Boi l th e resulting so llltio n o f calcium
hydrogen ca rbo nate.
• Preparatio n of sulfur tri oxid e. Pass dry oxygen
and sulfur diox id e over h eated platinised mineral • Actio n of heat, if any, o n sodillm , zinc and copper
wool. Collect sulfur tri oxid e as a solid in a cooled carbo nates.
rece ive r.
• Reaction of acids with a selectio n o f carbo nates.
• Reaction o f sulfur triox ide with water - care is • Formati o n of inso lu b le carbo nates by precipitation.
need ed. Test the solutio n to sh ow that it is acidic
(usin g b o th universal indicator and mag nesium Add aqueous sodium carbonate to solutions of
powder), and th at it contains sulfate io ns (by copper sulfate, calcillm chloride and nickel sulfate.
adding acidified barium chloride solutio n ).
Dilute sulfuric acid Carbon dioxide
• Reaction with mag nesillm and zinc. R • Laboratory preparation o f carbon dioxid e and its
• Reaction with bases - C uO and NaOH (aq ). properties (Figure 13. 16, p. 2 14).
• Reaction with carbonates - NiC03, CoC03 and
• Demo nstrate that carbo n and carbon-containin g
Na2C03'aq). compo unds fo rm carbon diox id e o n combustio n.
• Precipitati on o f insolubl e sulfates o f barium, lead Burn a variet y of materials and test for carbon
dioxide with limcwater. Suitable materials arc a
and calcium. candle, wood shavings, charcoal, paraffin etc.
16 EXPERIMENTAL CHEMISTRY
Chapter 14 Organic chemistry 1 • Reactio n with bases - sodium hyd roxid e
solutio n , coppcr(11 ) oxid e and magnesium oxide.
• Dem on strat e combll stion o f some alkan cs. U se a
Bunsen b urne r t o sh ow co m p le te and incomplete • Reactio n with an indicator - litmus.
co mbu stio n o f m e than e. Burn a range o f alkancs t o • Sh ow that cthan oic acid is a weak acid - a
show the varia tio n in case o f igniti o n - pc ntan c and
hexane arc highly fl ammable but liquid paraffin and comparative study with h yd rochlo ric acid.
paraffin wax n eed pre-heating and/or a wick. • Measure the pH ofO .l mol dm-3 solutio ns of
• Reactio n o f alkcncs with bromine. both acids.
• Cracking of alkan cs as d escri bed in the text • M easure th e conductivity o f 0.1 m o l dm-3
(Figm e 14.11 , p. 224 ). solutio n s o f bo th acids.
• Test fo r un saturatio n u sing bromine in a suitable • M easure the time taken for a short len gth o f
solvent (Figure 14.1 3, p. 225 ). m agnesium ribbon to react with 1.0 m ol dm-3
• D em on stration o f th crmosoftcnin g and solutio ns of both acids.
• Formatio n o f esters ( p. 237 ).
th ermosetting plastics. H eat sm all samples o f
po ly(cthenc ) and melamin e. Soaps and detergents
Chapter 15 Organic chemistry 2 • Making soap fr om vegetable oil and alkali. Bo il a
vegetable o il or animal fat with aqu eou s sodium
Ethanol hyd roxide . Cool and add salt to precipitate the
soa p.
• Combustio n o f ethan o l in a sm all spirit lamp to
d em on strate that it burn s with a sm all blm: fl ame . • Preparatio n o f a soapless d etergent fro m a
vegetable o il.
• Add ethano l to water to sh ow that the two liquids
arc miscible . Amino acids
• Show examples o f eth ano l as a solvent. • Id entificatio n o f amino acids by ch romatography.
• Oxidati on o f ethan o l by th e air. Use a water pump U se a 4 : I : 2 mixture o fbutan o l, ethan o ic acid
and water as a so lvent. Dry the ch romatogram and
to bubble air th roug h dilute aqu eous ethano l. R d evel op with a ninhydrin spray.
• Add eth ano l d ropwisc to a warm mixture o f
• Biurct test fo r proteins. Warm the sample in water,
potassium dich romatc(VI ) and dilute sulforic acid. R add con centrated sodium hyd roxide solutio n and a
• Formation o f esters using eth ano l and high er d rop o f very dilute coppcr( n ) sulfatc solutio n.
alcoh o ls. Mix 1 cm 3 o f ethan o l and 1 cm 3 o f glacial Plastics and polymers
cthano ic acid. Add 2 d rops o f concentrated sulfuric
acid and warm th e mixture fo r a few minutes. Then • The ' n ylo n rope trick' . The diamine,
pour the mixture into a beaker o f cold water. The 1,6-diamin o hcxanc, is dissolved in water to
distinctive smell o f an ester can be d etected. Repeat which some sodium carbo nate has been added. A
th e procedure using high er alco ho ls - p ropano l, solution of a diacid chlo ride, adipoyl chl oride, in
butano l and pentan o l. cycl o hcxanc is add ed and a nylo n thread can b e
• M aking ethano l by ferm entatio n ( Fi gure 15.8 , pulled fro m the interface between the t wo phases.
p. 23 6 ).
• Fractio nal distillatio n o f a mixture o f water and • Making a solid foa m. The ingredients fo r m aking
ethano l, u sin g the apparatus shown in Fig ure 2.22 a po lyurethan e foam can be purchased as a
(p. 21 ). N o te that this procedure may b e illegal in d em o nstratio n kit.
som e countri es.
Starch and glucose
Ethanoic acid
• Tests fo r starch and g lucose . Test fo r starch
• Sh ow th at ethan oic acid is an acid. using dilute aqu eou s io dine and for glu cose with
• Reactio n with m etals - mag nesium and zinc Fchling's solutio n o r Benedict's reagent.
powd ers.
• Reactio n with carbo nates - aqu eous sodium • H yd rolysis o f starch (p . 242 ). Use the tests above
carbo nate and copper(n ) carbo nate. to show that glu cose is fo rmed and starch is used
up wh en aqu eou s starch is bo iled with dilute
hyd rochloric acid.
Notes on qualitative analysis
• Notes on qualitative Fl ame co lo urs
analysis
If a clean nichrome wire is dipped into a m etal
The branch o f chemistry that d eals with the compo und and the n held in the ho t part o f a
identificatio n o f elem ents o r grouping o f elem ents Bunsen flam e, the flam e can beco me coloured
present in a sample is called qualitative chemical (Figure 16 .3 ). Certain metal io ns may be d etected
analysis , or qualitative analysis for short . It docs in their com pounds by o bservin g their flam e colours
n ot d eal with an ything to d o with quantities . (T,blc 16.2).
Th e techniques employed in qualitative analysis
vary in their co mplexity, d epending on th e nature
o f the sample under investigation . ln som e cases it
is o nly necessary to confirm the presen ce o f certain
elements o r groups fo r which specific chemical tests,
or 'sp ot' tests, applicable directly to the sample, may
be available . More o ften, th e sample is a complex
mixture, and a systematic analysis mu st be made in
ord er that all th e compo nent parts may be id entified.
Often, th e first simple stages o f qualitative analysis
require n o apparatus at all. Things like colour
and smell can be o bserved witho ut any need fo r
apparatus.
Th e fo llowing summary collects together
informatio n fro m th rou gh o ut th e book which would
all ow you to carry o ut qualitative analysis.
Appea rance or sme ll
A preliminar y examinatio n o f the substance will g ive
you a start. The appearance o r smell o f a substance
can o ften indicate what it mig ht contain (sec
T,bk 16.1 ).
Tab le 16.1 Deductions that can be made from a !;Ubstance's appearance
or smell.
Observation on substance Ind ication Figure 16.3 Thegreencolourischaracteristicofcopper.
Black powder Carbon, or conta ins 0 2- ions (as in
CuO), ors1- ions(as inCuS) Tab le 16.2 Characteristic flame colours of some metal ions.
Pale green crystals
Dark green crystals ContainsFe2-+ ions(asiniron(1)salts) Meta l Flame co lour
Blue or blue-green crystals Con tainsNi2+ions(as innickel(1) Group I Lithium Crimson
salts) Sodium Golden yellow
Yelk:rw-browncrystals Contains Cu1+ ions (as in copper{1) Group II Potassium Lilac
Smell of ammonia salts) Others Rub idium Red
Caesium Blue
ContainsFe* ions(asiniron(1)salts) Calcium Brick red
Strontium Crimson
Con tains NH/ ion s (as in ammonium Barium Apple green
salts) Lead Blue-white
Copper (as Cu(1)) G=o
16 EXPERIMENTAL CHEMISTRY
A fl ame colo ur is o btained as a result of the electro ns Tabl e 16.4 Effect of adding aqueous ammonia to solutions containing
in the particular io ns being excited when they absorb various metal ions.
energy from the fb.m c which is then emitted as visible
light. The different elect ronic structures o f the different Add eddropwis e To exc ess Cation present
io ns, therefore, give rise to the diftCrcnt colo urs.
Gelatinous blue Precipitate dissolves to give cu2+
precipitate adeepblueclearsolution
,,,.
Dirty green precipitate Precipitate does not dissolve
Tests for aqueous cations
Rustbrovvn Precipitate does not dissolve Fe*
precipitate
Effect of adding dilute sodium hydroxide
solution White precipitate Precipitate does not dissolve Al*
White precipita te
Aqueous sodium hyd roxide can be used to identi fy Precipitate dissolves zn2+
salts o f AI3+ Ca2+ C r3+ C u 2+ Fc2+ Fc3+ Pb2+ and
Zn2+ when ~rcsc,;t in a~u cou: solL1~i o ns.' All m etal No precipitate No precipitate Cal+
catio ns fo rm insoluble hyd roxid es when sodium
hyd roxide so lutio n is add ed to them. The colour of Light green Precipitate dissolves to c,*
the precipitate and its behaviour in excess sodium precipitate
hyd roxid e so lutio n will help id entify the metal
present (Table 16 .3). Tests for aqueous anions
Tabl e 16.3 Effect of adding sodium hydroxide solution to solutions Table 16 .5 sh ows a variet y o f tests fo r aqu eou s
containing various metal ions. ani ons.
Table 16.5 Tests for aqueous anions.
Added dropwise To excess Lik ely cation Anion Test Test result
White precipitate A13+,zn2+orPb2+ Carbonate(co/ - ) Effervescence,carbon
White precipitate Precipitate dissolves Ca2+ Add dilute acid dioxide produced
Chloride(CI- ) White ppt.
Blue precipitate Precipitate does not cu2+ [in solution) Acidifywithdilute
dissolve nitricacid,thenadd Creamppt .
Green precipitate ,,,. Bromide{Bo) aqueous silver nitrate
Precipitate does not ,,,. [in solution) Yellowppt.
Brovvnprecipitate dissolve Acidifywithdilu te
CrJ+ lodide(I-) nitricacid,thenadd Ammonia produced
Light green Precipitate does not [in solution) aqueous silver nitrate
precipitate dissolve Whiteppt.
Nitrate(N03- ) Acidifywithdilu te
Precipitate does not [in solution) nitricacid,thenadd Sulfurdioxide
dissolve aqueous silver nitrate produced will
Sulfa te{so/-J turn acidified
Precipitate dissolves [in solution) Add aqueous sodium aqueous potassium
hydroxide, then manganate(vw)from
( In the case o f ammo nium salts, ammo nia gas is Sulfite(so/- ) alum iniumfoil;warm purple to colourless
p roduced o n warming. The amm o nium cati o n d ocs carefully
n ot fo rm an insoluble hydroxid e. H owever, it fo rm s
ammo nia and water upon heatin g.) Acidify,thenadd
aqueous barium
Effect of adding dilute ammonia solution nitrate or barium
chloride
Ammo nia gas dissolved in water is usually known
as aqueou s ammonia. The solutio n is only weakly Add dilute
alkalin e, which results in a relatively low concentratio n hydrochloric acid,
o f h yd roxid e io n s. Aqueous ammo nia can be u sed warm gently and test
to identify salts o f AJ 3+ Ca1+ C r3+ C u1+ Fe1+ Fe3+ for the presence of
Pb1+ and Zn1+ io n s. Tl~e col~ur o f· the p'recipi~atc ' sulfurdioxi de
or solutio n fo rmed identifies the m eta.I present
(T, bk 16.4 ).
Notes on qualitative analysis
Tests for gases
Table 16.6 sh ows the co mmo n gases which may be
produ ced d uring q ualitative an alysis and tests which
can be used to idcntif)1 them. These tests arc u sed in
conjun ctio n with the tests sh own above.
Tabl e 16.6 Tests for gases.
Gas Colour(odour) Effect of moist indicator paper Test
Hydrogen (H1) Colourless (odourless) No effect - neutral 'Pops' inthepresenceofalightedsplint
Oxygen (02) Colourless (odourless) No effect - neutral
Carbon dioxide (C01) Colourless (odourless) Pink - weakly acidic Relights a glowing splint
Ammonia (NH 3) Colourless (very pungent smell} Blue - alkaline Turns limewater a cloudy white
Turns moist indicator paper blue - it is the only
alkaline gas
Sulfur dioxide (SO) Colourless (very choking smell) Red - acidic • Tums acidified potassium dichromate(~) from
orange to green
• Tums acidified potassium manganate(w) from
purple to colourless
Chlorine(Cl1) Yellow-green (very choking smell) Bleaches moist indicator paper Bleaches moist indicator paper
afterit initiallytumspalepink
Nitrogen(1V) oxide (N01) Brown (very choking smell) Pink-weakly acidic • Brown colour
• Tumsmoistindicatorpaperpink
Colourless(odourless) No effect-neutral • Tumsbluecobaltchloridepaperpink
• Tums anhydrous copper(1) sulfate from white
to blue
Questions to help your
understanding
1 For each of the following pairs of substances, describe a
chemical test you would carry out to distinguish between
them.
a potassium sulfate and potassium sulfite
b ammonium chloride and aluminium chloride
c zinc nitrate and calcium nitrate
d sodium chloride and sodium iodide
e iron(•) sulfate and copper(u) sulfate
2 Sodium carbonate hydrate contains water of crystallisation.
When it is heated strongly it gives off the water of
crystallisation, which can be collected.
a The substance left behind is anhydrous sodium sulfate.
Describe a chemical test to show that this substance
contains sodium (cation) and carbonate (anion).
b Describe two chemical tests to show that the colourless
liquid produced and collected is indeed water.
c Describe another test to show t hat the colourless liquid
given off in this experiment is water.
Q Revision and exam-style questions
Do not write in this book. \Vhcrc necessary copy Vo lume of acid C Thermometer Temperature/"(
drawings, tables or sentences. I~ :diagrams
added/cm3
• Alternative to 25
practical paper
I~:30
1 A student investigated the reaction of aqueous [2]
sodium hydroxide with two diffCrcnt acids, acid C Experiment 2
and acid D. The burette was emptied and rinsed with water.
Two experiments were carried out. Experiment l was repeated using acid D.
.Experiment 1 b Use the thermometer diagrams to record the
By using a measuring cylinder, 20cm3 ofaqueous
sodium hydroxide was poured into a conical flask and temperatures in the table of results.
the initial tcmpcranm:: ofthe solution was measured.
A burettc was filled with acid Cup to the O.Ocm3 mark. Tnbleofresu/ts
5 cm3 of acid C was added to the sodium
hydroxide in the flask. The temperature of the Vo lume of acid D Thermometer Temperature/"(
mixture was measured.
Further 5 cm3 portions of acid C were added to the added/cm3 I~:diagrams
0
mixture in the flask, stirring with the thermometer
until a total volume of 30 cm 3 ofacid Chad been I5 iji:
added. The temperatures after each 5 cm3 portion
had been added were measured.
a Use the thermometer diagrams to record the
temperatures in the table of results.
Table of remits I~:10
Vo lume of acid C Thermometer Temperature/"(
added/cml I~:diagrams 15
0
II~~:[20
5 I~:25
I~:30
II~:10 ij::
I~I:15
I~:20
[2]
Alternative to practical paper
c Plo t the results for Experim ents l and 2 o n the 2 Solid E was analysed. E was an aluminium salt.
g rid and draw two sm ooth line graph s. Clearly The tests o n the solid and som e o f th e o bservatio ns
label your graphs. arc in the following table . Complete the
o bservatio ns in the table.
Tests Observations
Tests on soli d.E.
a Appearance of solid E white crystalline solid
b A little of solid E was heated in colourless drops of liquid formed
a test-tube. at the top of the tube
30 c A little of solid E was dissolved
in distilled water.
The solution was divided
intofourtest-tubesandthe
following tests were carried out.
(i) To the first test-tube of [3)
solution, drops of aqueous
sodium hydroxide were added.
Excess sodium hydroxide was
then added to the test-tube.
(ii)Test(i)wasrepeatedusing [2)
aqueous ammonia solution
10 instead of aqueous sodium
hydroxide.
(i ii) To the third test-tube of no reaction
solu t i o n , d i l u t e h y d r o c h l o r i c
acid was added, followed by
barium chloride solution.
0 (iv)Tothefourth test-tube of effervescent pungent gas given
0 10 15 20 25 30 solution,aqueoussodium off turned damp litmus paper blue
vol ume of acid added/c m 3 hydroxide and aluminium
powder were added.
The mixture was heated.
[6] d What d ocs test (b) tell you about solid E ? [ l J
d From your graph, dedu ce the temperature of e ldcntifythegasgiven off intest(c)(iv). [l]
th e mixture when 3 cm 3 of acid C reacted with
f VVhat conclu sio ns can you draw about
sodium hyd roxide in Experiment l. solid E ? [2]
Show clearly on the graph how you worked out {Total: 9/
your answer. [2J (Cambridge /GCSE Chemistry 0620 Paper 61
e (i) Which experim ent produ ced the larger Q5 June 201 O)
temperature chan ge? [l ] 3 H ydrated co balt chlo ride crystals, CoC12 .6H2 0 ,
were heated in the apparah1s sh own below.
(ii) Suggest why th e temperature chan ge is
g reater in this experiment. [2]
f Why was the burcttc rin sed with water in
Experim ent 2? [l ]
g Predict the temperature of th e reactio n mixture w
in Experiment 2 after l ho ur. Explain your
[2]
[Total: 18]
(Cambridge /GCSE Chemistry 0620 Paper 61
Q4June2010)
REVISION AND EXAM-STYLE QUESTIONS
a Ind icate o n the d iagram , u sing an arrow, 6 Th e fo llowing in stru ctio ns were u sed to prepare
where heat is applied . [l] magnesium sulfate cr ystals, M gS04 .7H 20.
Step 1 M easure 50 cm 3 o f dilute sulfori c acid into
b The crystals ch an ge colo ur fr om _ _ to
[l] a beaker and warm the solutio n.
c W hat is the purpose o f tlu:: ice? [l] Step 2 Using a spatula , add som e m agn esium
d Why is the tube o pen at point W ? [l] oxid e and stir the mixture. Continu e adding the
[Total: 4} magnesium oxide until excess is present.
(Cambridge !GCSE Chemistf'f 0620 Paper 61 Step 3 Separate the excess m agn esium oxid e fr o m
Q6 June 2010) the solutio n o f m agn esium sulfate.
Step 4 H eat th e solution until crystals fo rm.
4 Malachite is a n aturally occurrin g fo rm o f copper Obtain the crystals and dry them .
carbon ate. O utlin e how a sample o f copper metal a W hy is the sulfuric acid warmed ? [ 1]
could be o btained fro m large lumps of malachite in b H ow would you know when excess magnesium
th e laboratory. oxide is present in Step 2 ? [ 1]
Cop per is o ne o f the least reactive m etals. Yo ur c W hat metho d is used in Step 3 1 [ 1]
answer sh ould includ e any ch emicals u sed and d W hy must care b e taken when drying the crystals
conditi o n s. [6] inStep4? [l]
[Total: 6} e E xplain how th e m eth od would differ if
(Cambridge !GCSE Chemistf'f 0620 Paper 61 magnesium carbo nate was u sed instead o f
Ql June 2010) magnesium oxide. [2]
(Total: 6}
5 Eth cn c can be prep ared by passing ethan o l vapour (Cambridge /GCSE Chemistry 0620 Paper 61
over ho t aluminium oxide.
Q2 November 2010)
7 A con centrated solutio n o f sodium chlo rid e was
elect rolysed u sin g th e apparatu s below.
ethene
mineral wool p o siti ve negative
electrode e lect ro d e
a Com plete the boxes to show the co ncentrated
aqueo us sodium chlo ride
ch emicals u sed . [l] and Universal Indicato r
b Show on the diagram with two arrows
where the h eat is applied . [2 ] One o b servati o n no ted was that the Universal
c W hy must the d elivery tu be be rem oved fr o m Indicator turned pmplc at th e negative electrode.
the water before th e heating is sto pped ? [2] a W hat o bservatio n would be mad e at both
(Total: S} elect rodes? [l]
(Cambridge !GCSE Chemistry 0620 Paper 61 b W hy did the indicato r turn purpl e at the negative
Q1 November 2010) elect rode? [ 1]
c (i) N am e the product fo rmed at the positive
electrode. [ 1]
(ii ) Su ggest th e effect o f this product on the
Universal Indicato r. [l]
(Total: 4}
(Cambridge /GCSE Chemistry 0620 Paper 61
Q6 November 2010)
Alternative to practical paper
8 E nllmbcrs idcnti f)1 chemicals which a.re add ed to Test O bservat ion
Test s on soli d .S.
foods .
a E2 10 is bcnzoic acid. H ow could yoll sh ow a Appearance of solid S black solid
slow effervescence
that a sollltion o f bcn zoic acid is a weak acid? b Hydrogen peroxide was added
to solid S in a test-tube.
t es t
res u l t [2] Aglowi ngsplint w asinserted splint relit
into the tube. blue solution formed
b E2 l l is sodillm ben zoatc. N am e a suitable
c Dilutesulfuricacid w asadded
substan ce that would react with a so lutio n o f to solid Sin a test-tube. The
mixture was heated to boiling
ben zoic acid to fo rm sodium bcn zoatc. [ 1] point .
c El 10 is Sunset Yel low. O utlin e a m eth od you
could use to show the presence o f E 11 0 in a
foo d colo uring. A space has been left if you Thesolution w asdividedinto
threeequalportionsintotest-
want to d raw a diagram to help answer tl1c tubes.
qu estio n . [4 ] (i) To the first portion of the [1[
solut ion,excesssodium [2[
(rota/: 7/ hydroxide w as added.
(Cambridge /GCSE Chemistry 0620 Paper 61 (i i) Tothesecondportionofthe
solution,about lcmofaqueous
07 November 2010) ammonia solution was added.
9 Describe a ch emical test to di stinguish between Excess ammonia solution w as [2[
then added. [2[
each of tl1e fo llowing pairs o f substances.
(i ii) Tothethirdportionofthe
An exam ple is g iven. solution, dilute hydrochloric
acid w as added folkmed by
Example: hyd rogen and carbon dioxide barium chloride solution.
test lighted splint
result with hyd rogen gives a pop
result with carbo n d ioxide splint is extinguished Test s on soli d V
a zinc carbonate and zinc chlo ride d Appearance of solid V black solid
rapid effervescence
t es t e Hydrogen peroxide w as added
tosolid V inatest-tube.
result witl1 zin c carbo nate
result witl1 zin c chlo ride [2] Aglow ingsplintwasinserted splint relit
into the tube.
b amm onia and chl o rine
t es t f (i) Compare tl1c reactivity of soli d S and
result witl1 ammo ni a solid V with h ydrogen perox ide. [l ]
result witl1 chlo rine [3] (ii) Identify the gas given off in test (e). [ l ]
c aqu eous iron ( n ) sul fu. tc and aq u eous iron( m ) g VVhat conclusio ns can you d raw about
sul fa te solid V1 [2]
t es t (rota/: 11/
result witl1 aqueous iron( n ) sulfa tc _ _ (Cambridge /GCSE Chemistry 0620 Paper 06
result witl1 aqu eous iron (m ) sulfa te _ _ [3] 05 June 2009)
(rota/: 8/
(Cambridge /GCSE Chemistry 0620 Paper 06 11 Acid base in d icators
03 June 2009) Indicators are used to id entify acid s and bases .
Ind icators can be obtained fr o m berri es and oth er
10 Two solids, S and V , were an alysed. S was fruits.
coppcr( n ) oxide.
The tests on th e solids, and som e o f tl1e a Plan an experiment to o btain an aq LJ cous
o bservations, arc in the fo llowing table.
Com plete the o bservati o ns in tl1e table. D o not solutio n ofan indi cator fro m som e be rries . [3]
write any con clusio ns in tl1c table.
b Plan an experiment to use the indi cato r
solutio n to show that it is an effective
indi ca t o r. [3]
(rota/: 6/
(Cambridge /GCSE Chemistry 0620 Paper 06
06 June 2009)
0
REVISION AND EXAM-STYLE QUESTIONS
12 The apparatus below was used to make oxygen. 14 Dilute hydrochloric acid was added to excess
The tube of manganese oxide was added to the calcium carbonate in a beaker as shown.
hydrogen peroxide solution by releasing the
cotton. cottoowool
calcium carbonate
hydrochloric
acid
balance
a Complete the boxes to idcntif).1 the pieces of The beaker was placed on a balance and the
mass of the beaker and contents recorded every
apparatus. [2] minute.
1l1e results arc shown in the table.
b Why was the tube of manganese oxide
suspended in the flask? [ 1] Mass of beaker 184.0 178.0 175.6 174.6 174.0 174.0
andcontents/g
c Give a test for oxygen.
Time/min
test
result [2] a Plot the results on the grid and draw a smooth
(Total: 5/ line graph.
(Cambridge /GCSE Chemistry 0620 Paper 06 Q1
November 2009)
13 Three unlabelled bottles of chemicals each
contained one of the following liquids:
• sodium nitrate dissolved in water;
• pure water;
• hcxcnc.
a Give a test by which you could identify sodium
nitrate solution.
test
result [2]
b Give a test by which you could identify pure
water.
test
result [2]
c Give a ti:st by which you could idmtify hexene.
test
result [2]
(Total: 6/
(Cambridge /GCSE Chemistry 0620 Paper 06 Q3
November 2009)
[5]
b Use your graph to determine the mass of the
beaker and contents after 30 seconds. Show
clearly on your graph how you worked out
your answer. [2]
Alternative to practical paper
c Why docs the mass of the beaker and contents a (i) Clearly label the electrodes on the
decrease? [ 1] diagram. [ 1]
d Suggest the purpose of the cotton wool. [ 1] (ii) Suggest a suitable material to make the
e After how long did the reaction finish? [ 1] electrodes. [1]
f A second experiment was carried out using b Give two observations expected when the lead
hydrochloric acid at a lower temperature. bromide is heated to melting point. [2]
On the grid sketch a curve to show the c State two different safety precautions when
expected results for this experiment. carrying out this experiment. [2]
Label this curve C. [2] (rota/: 6/
[Total: 12] (Cambridge /GCSE Chemistry 0620 Paper 06
(Cambridge /GCSE Chemistry 0620 Paper 06 Q2 June 2008)
Q6 November 2009)
15 Leaves from trees contain a mixture of coloured 17 Sulfur dioxide gas is denser than air and soluble in
water. A sample of sulfur dioxide can be prepared
pigments which arc not soluble in water. A by adding dilute hydrochloric acid to sodium
sulfite and warming the mixture. Study the
student was given these two instructions to diagram of the apparatus used.
investigate the pigments in the leaves.
1 Crush some leaves to extract the coloured
pigments.
2 Use the liquid extract to find the number of
coloured pigments in the leaves.
a VVhat would the student need in order to
effectively carry out instruction l? [3]
b Describe an experiment to carry out instruction 2.
A space has been left below ifyou want to draw a
diagram to help answer the question. [4]
(rota/: 7/
(Cambridge /GCSE Chemistry 0620 Paper 06
Ql November 2009)
16 The diagram shows an experiment to pass a Fill in the boxes to show the chemicals used. [2]
electricity through lead bromide. Electricity has
no effect on solid lead bromide. b Show by using an arrow, on the diagram, where
d .c. power supply heat is applied. [l]
D c Identify and explain two mistakes in the
LEAD diagram. [2]
BROMIDE
(rota/: 5/
TOXIC
(Cambridge /GCSE Chemistry 0620 Paper 06
t
Q3 June 2008)
heat
18 A student investigated the reaction between
potassium manganatc(v11) and a metallic salt
solution.
Two experiments were carried out.
Experiment 1
a About 1 cm3 of aqueous sodium hydroxide was
added to a little of the salt solution A and the
observation noted.
observation green precipitate formed
REVISION AND EXAM-STYLE QUESTIONS
b A burcttc was fill ed with potassium Table ofremits
m anganatc(vn) solution up to the 0. 0 cm 3 mark. Burcttc rcadings/cm 3
By using a measuring cylind er, 2 5cm 3 of
solutio n A of the salt was placed into a conical Exp eri men t 1 Experi men t 2
flask. The flask was shaken to mix the conten ts.
The potassium manganatc(vn ) solution was Final reading
added to the flask, and shaken to mix thoroughly. Initial read ing
Ad ditio n o f potassium m an gan atc(vr1 ) solutio n Difference
was continu ed until there was a pale pink colour
in the contents of the fl ask. [4]
Use th e burcttc d iagram to record th e volume
in the table and complete th e column . e ( i) In which experiment was the greatest
fi nal reading volume o f potassium m anganate(vn )
Experiment2 solutio n u sed ? [lJ
c E xperiment lb was repeated using a d ifferent
( ii) Compare th e volumes o f potassium
solutio n B o f th e salt, instead o f so lutio n A .
Use th e burcttc di agram s to record the man gan ate(vu ) solutio n used in
volum es in the table and co mplete the table.
Experiments l and 2. [2]
( iii )Su ggest an ex planatio n for the difference in
the volumes. [2]
f Predict the volume of potassium
m angan ate(v11 ) solutio n whi ch would be
n eed ed to react completely with 50cm 3 o f
solution B. [2]
g E xplain o n e chan ge that could be m ad e to the
experimental m ethod to obtain m ore accurate
results.
change _ _
explanatio n_ _ [2]
h W hat conclu sio n can you draw abo ut the salt
solution fr o m
(i) experiment la, [l]
(ii) experiment 2d? [l]
[Total: 15]
(Cambridge /GCSE Chemistry 0620 Paper 06
Q4 June 2008)
19 This label is fr o m a contain er o f 'Bite Relief'
solution .
BITE RELIEF
FOR FAST RELIEF FROM INS ECT BITESAND STI NGS
Acti ve in gredient : Amm o ni a
A lso contains wa t er and alco ho l
DIRECTIONS FOR USE: Use cotton wool t o dab the
so luti o n on the aff ect ed area of t he skin
a Give a chemical test to sh ow the presence o f
initial rea ding fin al read ing amm o nia in Bite Reli ef solutio n.
t es t
d About l cm 3 of aqu eou s sodium h yd roxid e was result [2]
add ed to a little o f the solution in the fl ask and
th e o bservatio n n oted . b W hat practical m ethod could be used to
o bservatio n red-brown precipitate
separate the mi xture o f alcoho l ( bp 78 °C) and
wotcc (bp l OO "C)? [2]
Alternative to practical paper
c Give a chemical test to show the presence o f 21 Ethcn c gas was fo rmed by th e crackin g o f a li quid
alkan c . The diagram sh ows th e apparatu s u sed.
water.
t es t
res u l t [2] liquid alkane
onmineral aluminium
d What would be the effect of touching the fibre oxid e
alcoh o l with a lighted splint? [ 1]
(rota/: 7/
(Cambridge /GCSE Chemistry 0620 Paper 06 /
Ql June 2008) ve ry stro ng
heat
20 The colou rs present in som e blackcurrant sweets a Identify two mistakes in the diagram . [2]
can be separated by chrom atography. The co lo urs
arc water- solu ble d yes. The diagram s sh ow h ow
the colo urs can be extracted fro m the sweets.
b D escribe a test to sh ow th e presen ce o f ethen c.
test
res u l t [2]
(rota/: 4/
(Cambridge /GCSE Chemistry 0620 Paper 06
Q3 November 2008)
a Complete the empty b oxes to nam e the pieces 22 An experiment was ca rri ed o ut to d etermine
th e solubility o f po tassium chl orate at diffe rent
of apparatus. [3] temperatures. The solu b ility is the m ass of
p o tassium chl o rate that dissolves in 100 g o f
The apparatus below was used to carry o ut the water. The resul ts o btained arc sh own in the
chrom atography. tab le below.
Temperature/" ( 0 10 20 30 40 50 60
So lubility in g/ 100gwater 12 17 20 24 29 34 40
a O n the grid , d raw a sm ooth lin e g raph to sh ow
the solubili ty o f potassium chlo rate at different
temperatures. [4 ]
40
b (i) Nam e the solvent used. [l ] t 20
(ii) Label, with an arrow, the o ri gin o n the :g
diagram . [l ] "§ 10
c Sketch the ch rom atogram you would expect 0
0
if two different colou rs were present in the
sweets. [l ] 10 20 30 40 so 60 70
(rota/: 6/ temperature/"(
(Cambridge /GCSE Chemistry 0620 Paper 06
Q1 November 2008)
REVISION AND EXAM-STYLE QUESTIONS
b Use your graph to dctr:rminc the solubility of b What is the purpose of D? [ 1]
potassium chlorate at 70 °C. Show clearly on c How could the purity of the ethanol collected
the graph how you obtained your answer. [2] be checked? [ 1J
c What would be the cffCct of cooling a saturated (Total: 5/
solution of potassium chlorate from 60 °C to (Cambridge /GCSE Chemistry 0620 Paper 06
20 "C? [2] Q1 June 2007)
(Total: 8/
(Cambridge /GCSE Chemistf'f 0620 Paper 06 25 Concentrated hydrochloric acid can be
electrolysed using the apparatus shown.
Q6 November 2008)
23 A solution of magnesium sulfatc can be made by
reacting magnesium oxide with warm sulforic
acid.
a Describe how you could make a solution of
magnesium sulfatc starting with magnesium
oxide powder and dilute sulfuric acid. [3]
b Describe how you would obtain pure dry
crystals of hydrated magnesium sulfatc,
MgS04.7H20, from the solution of [3]
magnesium sulfatc in a. (Total: 6/
(Cambridge /GCSE Chemistf'f 0620 Paper 06
Ql November 2008)
24 A mixture of ethanol and water can be separated
by fractional distillation. The apparatus below
can be used to carry out such a separation in the
laboratory.
a Label the position of the electrodes on the
diagram. [l]
b Give two observations when the circuit is
switched on. [2]
c (i) Name the product at the positive [ 1J
electrode.
(ii) State a test for this product and the result
of the test.
test
result [2]
(Total: 6/
(Cambridge /GCSE Chemistry 0620 Paper 06
02 June 2007)
a Name each piece ofapparatus. [3]
Alternative to practical paper
26 C h romatogr.i.phy can be used to id entify amino 28 Seawater contains sodium chlo ride and o ther
acids fro m a sample o f protein.
The diag ram shows the ch rom atogram obtained salts.
wh en four samples o f amino acids were analysed.
The pa per was sprayed with ninhydrin. Plan an experiment to find the mass o f salts in
1 dm 3 o f seawater.
solvent fro nt
You will be provid ed with a sm all bo ttle o f
seawa t er.
Yo u sho uld incl ude d etails o f the m eth od and an y
apparatus used. [6]
(1 dm 3 = 1000cm3)
(rota/: 6/
• (Cambridge /GCSE Chemistry 0620 Paper 61
•
Q6 October/November 2011)
ch ro mat ography 29 T wo different salts, D and E , were analysed .
p aper D was an aqu eous solution ofi ron(lll ) chloride
and E was a solid.
origin The tests o n the salts and som e o f the
o bser vations arc in the fo llowing table .
Complete the o bservati o ns in the table .
---- level of solvent Tests Observat ion s
o rigin al p ositions of a (i) Appearance of solid D [1)
samples of amin o acid s
(ii) Appearance of solid E w hite crystals [1)
[2)
Tests on solution D [2)
[1[
a Why is the origin line drawn in pencil ? [l ] b The solution w asdividedinto
four equal portions in test-
b Which amino acid s could possibly be tubes,andthefollowingtests
carried out.
thcsamd [l]
c VVhich amino acid sample contains m o re than (i) Dilutehydrochloric acid w as
added to the first portion
on e amino acid ? Explain your answer. ofthesolution andthen
sample _ _ aqueous barium chloride.
explanatio n _ _ [2] (ii) Dilutenitricacidwasadded
to the second portion and
d Su ggest why it is necessary to spray the then aqueous silver nitrate.
chromatogr.i.m with ninhydrin. [l ]
(rota/: 5/
(iii) An excess of aqueous
(Cambridge /GCSE Chemistry 0620 Paper 06 sodiumhydroxide w as
added to the third portion
Q3 June 2007) of the solution .
2 7 \V:h cn cem ent powder is add ed to water a reacti on (iv) Anexcessofaqueous
ammonia w as added to the
takes place. fourth portion.
:i D escribe an experiment to sh ow that this [4 J Testonso lidE
reactio n is exothermic.
c (i) Solid E w asheatedina limewater turned milky
b H ow could you show that the solution test-tube.
co ntains calcium ions? [2] Thegasgivenoff wastested .
(rota/: 6/ (ii) Dilute nitric acid w as added rapid effervescence,
(Cambridge /GCSE Chemistry 0620 Paper 06 to solid E in a test-tube. limewater turned milky
Q7 June 2007)
REVISION AND EXAM-STYLE QUESTIONS
d Identify th e gas g iven off in tests (c)(i) [tJ • Theory
and (c)(ii).
Papers 21 and 22 arc Core theory papers; Papers 3 1,
e W hat conclusion s can you draw abo ut 32 and 33 arc E xtended th eory papers.
solid E ? [2] D o no t write in this boo k. Where necessary copy
drawin gs, tables o r sentences.
(rota/: 10/
Physical
(Cambridge /GCSE Chemistf'f 0620 Paper 63
QS October/November 2011)
30 Three diffCrcnt liquid s P , Q and R were analysed. 1 Th e diagram below shows the elements in a period
P was an aqueou s solutio n of sulfuric acid . o f th e Periodic Table .
The tests on the liquids and some of the
o bservatio n s arc in the followin g table. I L, I ,, I B I C I N I O I F I N, I
Complete the o bservatio n s in th e tabk.
Tests Ob servations :i To which p erio d o f the Perio dic Table d o these
a (i) Appearanceof theliquids [2)
Q colourless, smell of vinegar elem ents belon g? [ 1J
R colourless, no smell b Answer these qu esti on s using o nly the elem ents
Q pHS
{ii} The pHof theliquidswas R pH7 [2) shown in th e diagram. Each clement can be u sed
tested using Universal Q sloweffervescence [2)
indicator paper. R noreaction o nce, m o re than o nce or n ot at all.
[2)
b A piece of magnesium ribbon temperature= 100°( Write d own the symbol for the clement which
was added to a little of each
liquid. (i) has six elect ron s in its o uter shell.
Thegasgivenoffby liquid P
was tested. (ii) is a halogen.
c Toalittleofliquid P, (iii)is a metal which reacts rapidly with cold water.
hydrochloric acid and aqueous
barium chloride were added. (iv) has two fo rms, graphite and diamo nd.
d Liquid R was heated to boiling (v) is in G roup II o f the Perio dic Table.
in a test-tube. A thermometer
wasused torecordthe (vi) makes up abo ut 80% o f the air. [6]
constant temperature of the
vapou r produced. c Complete the fo llowing sentence u sing word s
fr om the list below.
:itmns electrons molecules
neutrons protons
e W hat conclusion s can you draw abo ut The o f the elem ents in the Periodic
liquidQ? [2] T able are arran ged in ord er o f in creasing number
of [2]
f Identify liquid R [l ]
(rota/: 9/
(rota/: 9/
(Cambridge /GCSE Chemistry 0620 Paper 2 1
(Cambridge /GCSE Chemistry 0620 Paper 61
Q1 November 2010)
QS October/November 2011)
2 Abo ut 4000 years ago the Bron ze Age started in
Britain. Bron ze is an alloy o f copper and tin .
a (i) Su ggest a reason why a b ron ze a.xc was
better than a copper axe . [ 1]
(ii) Brass is an oth er copper alloy. Nam e the
oth er m etal in brass. [ 1J
Theory
b The diagram shows the arrangement of particles 3 Soluble salts can be made using a base and an acid.
in a pure metal.
a Complete this method of preparing dry crystals
of the soluble salt cobalt(n) chlorid c -6-water
from the insoluble base cobalt(n ) carbonate.
Step 1 Add an excess of cobalt(n) carbonate to
hot dilute hydrochloric acid.
Step 2
Step 3
Step 4 [4]
(i) What is the name given to a regular b 6.0g ofcobalt(n) carbonate was added to 40cm3
of hydrochloric acid, concentration 2.0moJ/dm3.
arrangement of particles in a crystalline
Calculate the ma..'l;:imum yield of cobalt(n)
solid> [l ]
chloride-6-watcr and show that the cobalt(n)
(ii) Draw a diagram which shows the
carbonate was in excess.
arrangement of particles in an alloy. [2]
CoC03 + 2HCl-----+ CoC~ + C02 + H 20
(iii)Explain the term ma/leablc. [l]
(iv) Why arc metals malleable? [2] CoCt, + 6H 20 - CoCt,.6H 20
c The common ore of tin is tin (rv) oxide and an
ore of copper is malachite, CuC03.Cu (OH)i. Maximum yield
(i) Write a word equation for the reduction of
Number of moles of H Cl used=
tin(1v) oxide by carbon. [ 1] Number of moles of CoC12 formed = _ _
Number of moles ofCoC12.6H 20 formed
(ii) Malachite is heated to form copper oxide
and two other chemicals. Name these
chemicals. [2] Mass of one mole ofCoC12 .6H2 0 = 238g
Maximum yield ofCoC12 .6 H 20 = _ _ g [4]
(iii)Coppcr oxide is reduced to copper which To show that cobalt(n) carbonate is in excess
is then refined by electrolysis. Label the
diagram of the apparatus which could be Number of moles of H Cl used= _ _ (use
used to refine copper. [ 3] value from above )
power Mass of one mole of CoC03 = 119 g [l ]
supply Number of moles of CoC03 in 6.0 g of
cobalt(n) carbonate = _ _
Explain why cobalt(11 ) carbonate is in excess. [ l ]
[Total: 10]
(Cambridge /GCSE Chemistry 0620 Paper 31
QB November 201 OJ
4 The list describes five types of chemical structures.
(iv) Give one use of copper, other than making giant covalent
giant ionic
alloys. [l ] metallic
[Total: 15] simple atomic
simple molecular
(Cambridge /GCSE Chemistry 0620 Paper 31
a The diagrams below show four types of chemical
Q2 November 201 OJ structures.
A
REVISION AND EXAM-STYLE QUESTIONS
(i) Use the li st to match these structures with b The only difference in the two experiments was
the method used to hold down the magnesium.
the diagrams. The results arc shown.
Structure A is [l ]
Structure B is [l ]
Structure C is [l ]
Structure D is [l ]
(ii) Which two of the structurt:sA, B , C and D
have low melting points? [I]
b Sodium ch loride is an ionic solid. Complete the
following sentences using words from the list. magnesium held
down by plastic
electrons ionic molecular molten solid
Sodium ch loride docs not conduct electricity
when it is a because the ions cannot
move. When it is sodium chloride docs time/s
conduct electricity because the ions arc fo::c to
[2] (i) In which experiment did the magnesium
(Total: 7/
react faster? [l]
(Cambridge /GCSE Chemistf'f 0620 Paper 22 (ii) Suggest a reason why the experiment chosen
Q2 June2010) in (i) had the faster rate. [l]
c The experiment was repeated using l .OmoJ/dm3
5 A diagram of the apparatus which cou ld be used to propanoic acid instead of l.OmoJ/dm3
investigate the rate of reaction between magnesium
;md an excess of an acid is drawn below. hydrochloric acid. Propanoic acid is a weak acid.
(i) H ow would the graph for propanoic acid
differ from the graph for hydrochloric
volume of hydrogen hydrogen collects acid ? [l]
measured every
15seconds (ii) H ow would the graph for propanoic acid be
the same as the graph for hydrochloric
acid? [l]
d Give two factors which would alter the rate of
graduated tube this reaction. For each factor explain why it alters
the rate. [4]
[Total: 10]
(Cambridge /GCSE Chemistry 0620 Paper 31
Q3 June2010)
110 cm3 ofacid 6 Iodine reacts with chlorine to form dark brown
1.0mol/dm3 (excess) iodine monochloride.
small piece of 12 + c1,_ -21c,
magnesium
This reacts with more chlorine to give yellow
a The magnesium kept rising to the surface. In iodine trichloridc. There is an equilibrium between
one experiment, this was prevented by twisting these iodine chlorides.
the magnesium around a piece ofcopper. ln a
second experiment, the magnesium was hdd IC/(!) + Ci,(g) ;=: IC/3(s)
down by a plastic net fastened to the beaker.
(i) Suggest a reason why magnesium, which is a Explain what is meant by equilibrium. [2]
denser than water, floated to the surface. [ 1]
(ii) Iron, zinc and copper have similar densities. b When the equilibrium mixture is heated it
Why was copper a better choice than iron or
zinc to weigh down the magnesium? [ 1] becomes a darker brown colour. Is th e reverse
reaction endothermic or exothermic? Give a
reason for your choice. [2]
Theory
c The pressure on the equilibrium mixture is around the negative ion.
decreased. Use o to represent an electron from an
(i) How would this affect the position of atom of C.
equilibrium and why? Use x to represent an electron from an atom
It would move to the [l] of F. [3]
[l] (ii) Predict two properties of this
(ii) Describe who.t you would observe. [l] compound. [2]
{Total: 7/ {Total: 10/
(Cambridge /GCSE Chemistry 0620 Paper 31 (Cambridge /GCSE Chemistry 0620 Paper 31
Q6 June 201 O) Q3 June 2009)
7 Some grass is crushed and mixed with the solvent, 9 Quantities of chemicals, expressed in moles, can be
propanone. The colour pigments arc extracted to used to find the formula of a compound , to establish
give a deep green solution. an equation and to determine reacting masses.
a (i) Dro.w a labelled dio.gram to describe how a A compound contains 72% magnesium and 28%
you could show that there is more than one nitrogen. What is its empirical formula? [2]
coloured pigment in the green solution. [3] b A compound contains only aluminium and
(ii) Given a pure sample of chlorophyll, how carbon. 0.03 moles of this compound reacted
could you show that the green solution from with excess water to form 0.12 moles of
the grass contained chlorophyll? [2] Al(OHh and 0.09 moles ofCH4 .
Write a balanced equation for this reaction. [2]
b Explain the role ofchlorophyll in green
plants. [3] c 0.07 moles of silicon reacts with 25g of bromine.
{Total: 8/ Si + 2Br2 ---> SiBr4
(Cambridge /GCSE Chemistry 0620 Paper 31 (i) Which one is the limiting reagent? Explain
Q1 June 2009) your choice. [3J
8 The following is a list of the electron distributions (ii) HowmanymolcsofSiBr4 areformed? [l]
of o.toms of unknown elements. {Total: 8/
(Cambridge /GCSE Chemistry 0620 Paper 31
Element Electron d istribution Q9 June 2009)
A 2,5
2,8,4
2,8,8,2 10 a Link the terms in the boxes on the left with the
2,8,18,8
2,8,18,8,1 definitions on the right. The first one has been
2,8,18,18,7
done for you. [4]
a Choose an clement from the list for each of the a substance containing
following descriptions. different atoms or ions
( i) It is a noble gas.
(ii) It is a soft metal with a low density. bonded together
(iii)It can form a covalent compound with
element A. a substance made up of
(iv) It ho.s a gio.nt covalent structure similar to one type of atom
diamond.
(v) It can form a negative ion of the type X3- . thesmallestpartofan
[5] element which takes part
b Elements C and F can form an ionic compound. in a chemical reaction
(i) Draw a diagram that shows the formula of
this compound, the charges on the ions and the smallest group of
the arrangement of the valency electrons covalently bonded atoms
whichcanexistonitsown
a charged atom or group
of atoms
REVISION AND EXAM-STYLE QUESTIONS
b Which two of the following arc mixturcs1 b The energy released by the burning ethanol
Tick two boxes. raises the temperature of the water in the
air
D copper calorimeter.
graphite D (i) Which one of these words best describes
sodium chloride the energy change when ethanol burns?
D Put a ring around the correct answer.
steel D electrolytic electronic endothermic [ 1J
exothermic
[l ] (ii) When 4.6g of ethanol is burnt, 5.4 g of
c (i) Draw a labelled diagram to show the water is formed. Calculate the mass of
atomic structure ofan atom of helium. In water formed when 13.S g of ethanol is
your diagram include the structure of the burnt. [l]
nucleus. [4] (iii)Compkte the equation for the combustion
(ii) State a use for helium. [ 1] of ethanol.
(iii)Which one ofthese statements about
helium is correct? [l ]
helium is in Period 2 of the c The calorimeter is made of copper. Copper is
Periodic Table
D a transition metal. State two properties which
Dhelium is a liquid at room temperature distinguish transition metals from Group I
metals. [2]
D d \iVhen copper is left exposed to the air for some
helium is unrcactivc time, a coating of copper carbonate forms on
helium has an incomplete outer D its surface. The equation shows how copper
shell of electrons carbonate reacts with hydrochloric acid.
[l ] CuC03( , ) + 2 Hq,q) - CuC~(,q) + C02(g) + H20 (!)
(rota/: 11]
(Cambridge /GCSE Chemistry 0620 Paper 02 (i) Describe two observations that can be
Q2 November 2009) made as this reaction happens. [2]
(ii) State the meaning of the symbol (aq). [ 1 ]
e The calorimeter lid is made ofpoly( ethene ).
11 A student used the apparatus shown to calculate Complete these sentences about poly(ethene )
the energy released when ethanol burns. using words from the list.
thermometer acids addition condensation ethane
poly(ethene) lid -...,~---++--~ ethene monomers polymer
Poly(ethcne) is a _ _ formed by the _ _
copper ofethene molecules.
calorimeter
In this reaction the ethene molecules can be
clamp
described as [3]
(Total: t2/
(Cambridge /GCSE Chemistry 0620 Paper 02
Q3 November 2009)
ethanol
a Draw the structure of ethanol showing all
atoms and bonds. [ 1]
Theory
12 Caesium is a metal in Group I of the Periodic Table. 13 The table shows the concentratio n o f som e ions
a State two physical properties o f caesium. [2 ] present in seawater.
b State the number o f electro ns in the o uter ~Nam-e of-ion~Fo-rmu-la o-f ion~C-once-ntr-atio-n of-ion-in -g/ dm~3
shell o f a caesium atom. [l] bromide Br 0.07
calcium (aH 0 .4
c An isotope of caesium h as a mass number o fl 3 3. chloride 19.1
magnesium er 1.2
(i) What do you und erstand by the term
Mgi+
iso t ope? [l]
(ii) Calculate the number o f neutro ns in this
isoto pe o f caesium. [ 1] potassium K' 0.3
d Complete the fo llowing table to estimate sodium Na' 10.6
0.8
the b oiling point o f caesium and predict the so/-
reactivity o f caesium with water. a Which negative io n has the high est
Group I Density/ Boili ng Reactivity with water con centratio n in seawater? [ 1]
meta l g/ cm 3 pointl°C
sodium 0.97 883 fiu esquickly,disappearsgradually b State the name o f th e io n with the formula
0.86 760 and does not burst into flame
potassium so ,2 -. [l l
1.53 686 fiues veryquickly,disappears
rubidium quicklyandbursts intoflame w ith c Which two ions in the ta.bk arc fo rmed fro m
1.88 a little spitting
Group I elements? [ 1]
fiuesextremelyquickly,bursts
intoflamethenspits violently and d VVhcn seawater is evaporated a number o f
may explode
diftCrcnt compo und s arc fo rmed. State the
name o f the co mpound which is present in the
g reatest quantity. [l ]
e State the names o f two io ns in the tabl e
[2] which m ove to the catho de when seawater is
e The diagram sh o ws th e structure o f caesium
e lect r olysed . [2 ]
c hl o rid e.
f When concentrated seawater is elect rolysed ,
chlorin e is fo rm ed at on e o f the electrodes.
(i) To which Period in the Perio dic Table d ocs
chlo rine belo ng? [ 1]
(ii) Draw the electronic structure o f a chlorine
mo lecule. Sh ow only the outer electrons. [2 ]
g Drinking water can be o btained by purif)1ing
seawa te r.
Explain why distillatio n rath er than filtrati o n is
used to purify seawater fo r drinking . [2]
[Total: 11]
(Cambridge /GCSE Chemistry 0620 Paper 02
Q3 June 2008)
U se this diagram to work out the simplest 14 Fo r each o f the fo ll owing select an clem ent fro m
Perio d 4 , po tassium to krypton , that match es the
fo rmula fo r caesium chloride. [l ] d escription.
a It is a brown liquid at room temperature .
f Cai:sium chloride dissolvi:s in water to form b It form s a compo und with hydrogen having th e
fo rmula XH4 .
a neutral solutio n. State the pH o f a neutral c A m etal that reacts vio lently with cold water.
d It has a complete o uter energy level.
solutio n. [l ] e It has oxidatio n states o f2 and 3 o nly.
g D escribe a test for chl oride io ns. [2]
[Total: 11]
(Cambridge /GCSE Chemistry 0620 Paper 02
Q4 November 2009)
REVISION AND EXAM-STYLE QUESTIONS
f It can form an ion of the type x - 17 The following techniques arc used to separate
mixtures.
g One of its oxides is the catalyst in the Contact A simple distillation
Process. B fractional distillation
(Total: 7/
(Cambridge /GCSE Chemistry 0620 Paper 31
Q1 June 2008)
15 a Complete the table which gives the names, C evaporation
symbols, rdativc masses and rdativc charges of D chromatography
the three subatomic particles. E filtration
F diffusion
Nam e Symbol Relative mass Relative charge
electron
proton
From this list, choose the most suitable technique
[3] to separate th e fo llowing.
b Use the information in the table to explain the a methane from a mixture of the gases, methane
following. and ethane [ l]
(i) Atoms contain charged particles but they b water from aqueous magnesium sulfatc [ 1]
arc ckctrically neutral because they have no c glycine from a mixture of the amino acids,
overall charge. [2] glycine and lysine [ l]
(ii) Atoms can form positive ions. [2] d iron filings from a mixh1rc of iron filings
(iii)Atoms of the same clement can have and water [l]
different masses.
[2J e zinc su lfatc crystals from aqueous zinc
(iv) Scientists arc certain that there arc no sulfatc [l]
undiscovered elements missing from f hexane from a mixture of the liquids,
the Periodic Table from hydrogen to hexane and octane [l]
(Total: 6/
lawrencium. [ 1]
(Total: 10/ (Cambridge /GCSE Chemistf'f 0620 Paper 31
(Cambridge /GCSE Chemistf'f 0620 Paper 31 Q1 June2011)
Q2 June 2008)
16 Copper is purified by electrolysis. 18 1l1c apparatus shown below can be used to
a Complete the following. measure the energy released when a liquid foci
The positive electrode (anode ) is made from is burnt. The amount of energy released is
calculated from the increase in temperature of a
known amount ofwater.
The negative electrode (cathode ) is made from
The electrolyte is aqueous__ [3]
b Write an ionic equation for the reaction at the iron can
positive electrode (anode). [2]
c (i) Give two reasons why copper is used
in electric wiring, [2]
in cooking utensils. [2]
(ii) Give another use ofcopper. [l ]
(rota/: 10]
(Cambridge /GCSE Chemistry 0620 Paper 31
Q3 June 2008)
Theory
a (i) Explain how this experim ent shows that (ii) Diam o nd has a similar structure and
th e burning o f ethan o l is an exothermic consequ ently similar properti es . G ive
reactio n. [l ] two physical p roperties comm on to both
(ii) Complete the word equation fo r th e d iam o nd and silicon(1v) oxide. [2]
complete combu stio n o f ethanol. (Total: 14/
ethan o l + oxygen ----> _ _ + _ _ [2] (Cambridge /GCSE Chemistry 0620 Paper 31
Q2 November 2008)
b Ethan ol is a fu d containing carbon . State
th e nam es o f two oth er comm only used fu ds 20 The elect rolysis o f concentrated aqu eous sodium
containing carbon. [2] chl o rid e produ ces three commercially important
c Give th e fo rmula of the fun ction al group ch emicals: hyd rogen , chlorine and sodium
present in eth an ol. [ 1] hyd roxid e.
d The can contains water. Describe a ch emical a The ions present arc N a+(aq ), H +(aq ) ,C/(aq)
test for water. [2] and O H~ (aq ).
e The iron can used in this experiment rusts easily. (i) Co mpl ete th e ioni c equ ation fo r the
(i) D escribe a m ethod which can be used to reactio n at the negative elect rod e
prevent iron fr om rustin g . [ 1] (cathode ).
(ii) Rust contains h yd rated iron (m) oxide. What __ + __ -H, [l ]
d o you understand by the term hydrated? [ 1]
(iii ) Iron is a transition metal. State two properties (ii) Com plete th e io ni c equ ation fo r th e
which arc typical oftransition metals. [2] reactio n at the positive electrode (anode ).
(Total: 12/ __ + __ - et, [l ]
(Cambridge /GCSE Chemistry 0620 Paper 02
Q5 November 2008) (iii) Explain why th e solutio n chan ges fr om
sodium chloride to sodium hyd rox ide. [1]
19 There arc three types o f g iant stru cture -io nic, b (i) Why d ocs the water su pply industry use
metallic an d macrom olecular. chlo rine? [ 1]
a Sodium nitride is an io nic compo und. Draw (ii) N am e an impo rtant chemical that is m ade
a diagram th at sh ows th e fo rmula o f the fr o m hyd rogen. [ 1]
compo und , the charges o n the io ns and the (iii) H ow is sodium hyd roxide used to m ake
arran gement of the valency elect rons around soap? [2]
the negative io n. (Total: 1/
Use x to rqJrcscnt an electron from a sodium atom. (Cambridge /GCSE Chemistry 0620 Paper 31
U se o to represent an electro n fr o m a nitrogen Q5 November 2008)
atom . [3]
b (i) D escribe m etallic bonding . [3] 21 H elium and argon arc noble gases.
(ii) Use the above ideas to ex plain why: a State oneuscofh elium. [l ]
metals arc good conductors o f b The atomic structures ofhd ium and argon arc
el ectricity, [l ] sh own below.
metals arc m alleable. [2]
c Silicon (w ) oxide has a m acrom o lecul ar
structure . ( Y x ~\ _-:,
(i) D escribe the structure o f silicon (w ) oxid e
(a diagram is no t acceptable). [3]
heli u m argon
REVISION AND EXAM-STYLE QUESTIONS
(i) State th e name o f the cen tral part o f the 22 H ydrogen chl oride can be made by burning
hydrogen in chlo rin e.
atom , labelled X. [ 1] a Complete the eq uatio n for this reaction.
(ii) Which statement about helium and argon
is correct? Tick one box. H2 + __ - __ HC/ [2]
Argon has an in complete inner sh ell o f b Draw a dot and cross diagram for a molecule of
h ydrogen chloride . Sh ow all the electrons.
Dck:ctro n s. Use o fo r an electron from a hydrogen atom.
Use x for an electron from a chl orine atom. [2]
An atom of argon has 16 electro ns. D
c H ydrochlo ric acid is formed when hyd rogen
Helium has a complete outer shdl of D chloride gas dissolves in water. Su ggest the pH
o f hydrochloric acid. Put a ring around the
electrons. correct answer.
Helium has an incomplete outer shell o f pHl pH7 pH9 pH13 [l]
Delectro n s.
[l ] d Complete the equatio n for the reacti o n o f
hydrochloric acid with zin c.
(iii )How many protons arc there in an atom o f
argon? [l ]
(iv) The symbol for a particular isotope o f zinc+ hydrochloric acid ----,. zin c chloride + _ _
[l ]
helium is written as j H c.
Write a similar sym bol for th e isotope o f e Describe h ow dry crystals of zin c chl oride
argon which has 16 n eutrons. [ 1J can be obtained from a solutio n of zinc
c Argon is a liquid at a temperature o f - 188 °C. chl o ride . [2]
Complete the diagram below to sh ow h ow the f A student electrolysed m olten zin c chloride.
atoms of argon arc arranged at - 188 °C. State th e name of the product formed at:
Q represents o ne atom of argon. (i) the anode, [l]
(ii) th e cathode. [l]
[Total: 10/
(Cambridge /GCSE Chemistry 0620 Paper 02
Ql June 2009)
23 Sulfuric acid is a typical st rong acid.
a Change the equations g iven into a different
format.
[2] (i) Mg+ H2S04 ___,. MgS04 + H 2 [l]
Ch ange into a word eq uatio n.
[Total: 7/
(ii) lithium oxid e + sulfuric acid----,.
(Cambridge /GCSE Chemistf'f 0620 Paper 21
Q3 November 2010) lithium sulfate + water
Change into a symbo l eq uatio n. [2]
(iii)CuO + 2H+ ___,. Cu 2+ + H 2 0
Change the io nic equation into a symbo l
eq uatio n. [2]
(iv) Na2C03 + H 2S04 ___,. Na2S04 + C02 + H 20
[l J
Change into a word equation.
b When sulfuric acid dissolves in water, th e
fo llowing reaction occurs.
H 2S04 + H 20 ___,. HS04- + H 30+
Explain why water is behaving as a base in this
reactio n. [2]
Theory
c Sulfuric acid is a strong acid, cthanoic acid is a (ii) Draw a diagram to show the arrangement
weak acid. of the electrons in a molecule of methane,
Explain the difference between a strong acid CH4 .
Use
and a weak acid. [2]
(rota/: tO/ • for an electron from a carbon atom
(Cambridge /GCSE Chemistry 0620 Paper 31 x for an electron from a hydrogen atom. [1J
Q4 June 2008) (iii)Mcthane belongs to the alkanc
24 Three forms ofcarbon arc diamond, graphite and homologous series. [ 1J
Buckminsterfullerene. Name one other alkanc.
[Total: 13]
(Cambridge /GCSE Chemistry 0620 Paper 22
Ql June 2010)
Inorganic
25 Water is an important raw material in industry.
a State one use of water in industry. [ 1J
diamond graphite Buckminsterfullerene b Describe a chemical test for water.
test
a (i) State one difference in structure between result [2]
Buckminstcrfollerene and diamond. [ 1] c A small piece of potassium was placed in a
(ii) State two differences in structure between beaker of water.
graphite and diamond. [2J The equation for the reaction is
b State the type of bonding between the carbon 2K(s) + 2H,0 (1) - 2KOH (,q ) + H2(s)
atoms in diamond. [ 1] (i) Describe a test for the gas given off in this
c Suggest why gra.phitc is used as a lubricant. reaction.
Refer to the layers in your answer. [ 1] test
d State one use for dia.mond. [ 1] result [2]
e Coal is a fud containing carbon. When
(ii) What is the most likely pH of the solution
coal is burnt, carbon dioxide is produced.
Explain how the increase in carbon dioxide in the beaker when the reaction is complete?
concentration in the atmosphere affects the Put a ring around the correct answer.
world's climate. [2] pH2 pH6 pH7 pHB pH12 [l]
f Coal also con ta.ins small amounts of sulfor. d \Yater is formed when propane burns.
(i) Complete the equation for this reaction:
Explain how burning coal \cads to acid rain. [2]
g Methane is a foci. C3H 8 + 502 ---> _ _ C02 + _ _ H 20 [2]
(i) Which one of the following is a natur.i.l (ii) Which of the following best describes this
source of methane? reaction?
Put a ring around the correct answer.
Tick one box.
Dwaste gases from respir.i.tion in plants
Dwaste gases from digestion in animals c.."1rbonisation combustion
dehydration
hydrogenation [1J
gases from photosynthesis in plants D (iii)When 4.4g of propane arc burnt in
gases from forest fires D excess oxygen, 7.2g of water arc formed.
Calculate the mass of water formed when
[l] 22 g of propane arc burnt. [ 1J
[Total: 10]
(Cambridge /GCSE Chemistry 0620 Paper 22
Q3 June 201 O)
REVISION AND EXAM-STYLE QUESTIONS
26 a C h oose fr om the list o f compound s to an swer c W hich t wo o f these elem ents make up most o f
q u estio ns (i) to (v).
th e air1 [I]
calcium carbo na te carbon dioxide d Bromine and flu orine fo rm a com pound
hydrogen chloride
with th e for mula BrFs. Calculate the relative
iron(m ) oxide lead(n) bromide
methane sodium hydroxide m o lecular m ass ofBrF 5. [I]
e The diagram sh ows th e structure o f some
compo unds containing oxygen.
Each com pound can be u sed on ce, mo re than A
o n ce or n ot at all.
Nam e the compo und which
(i) is a tran sitio n metal compo un d, [l]
(ii) produ ces brown fom cs at the an ode when
elect ro lyse d , [ 1]
(iii ) is used to manu facture lim e, [ 1] ( i) W hat type of oxid e is com pound C? [ I ]
( ii) Com pound A is an atmosph eric po llutant.
( iv) d issolves in water to fo rm an alkaline
D escri be the source o f compo und A and
solutio n, [l ] state its effect o n the enviro nment. [2]
(iii) In the presence o f air, com pound D reacts
( v ) is the m ain constituent o f natural gas . [ l ] with water to fo rm nitric acid.
A student u sed the ap parah1s sh own to add
b At a hi gh tem perature iron ( m ) oxide is reduced an aqu eous solutio n of nitric acid to an
aqu eou s solutio n o f po tassium hydroxide.
by carbon. H e ad ded the acid until it was in excess .
Fc20 3 + 3C -----+ 2 Fc + 3CO
(i) Explain how th e equatio n sh ows that
iron( m ) oxide is reduced by carbon. [ 1]
(ii) Complete these senten ces ab o ut th e
extractio n o f iron u sing words fro m the
list .
bauxite blast co n ver ter haematite
lime limestone sand slag
Iron is extracted from _ _ by mixing
the ore with coke and in a
fornacc.
1l1c iron ore is reduced to iron and
imp urities in the ore react with calcium
oxide to for m [4 ]
(rota/: 10]
(Cambridge /GCSE Chemistry 0620 Paper 02
Q1 June 2009)
2 7 The list sh ows som e no n-metallic elem ents.
bromine D escri be h ow th e pH o f the soluti o n in
carbon
fluorine th e fl ask changes as the nitric acid is ad ded
krypto n
nitrogen
oxygen
a W hich two elem ents in the list arc in the sam e until the acid is in excess. [3]
Group of th e Peri odic T ab le? [I]
b W hich clem ent in th e list has the high est
proto n number? [l ]
Theory
(iv) D escribe how you can m easure this pH
chan ge . [l ]
( v) The equatio n for the reaction is burette
hy d roc hlori c
acid
State the name o f the salt fo rmed in this
reaction . [l ]
{To tal: 12/
(Cambridge /GCSE Chemistry 0620 Paper 02 Q 1
November 2009)
28 A solutio n o f calcium hyd rox ide in water is ""A-=-=-=-=
alkalin e.
a Which o n e o f the pH valu es below is alkaline?
Put a ring around th e correct answer.
pH3 pH6 pH ? pH ll [l ]
b Which o f the following is the commo n name solution of
fo r calcium hyd roxide? calcium hydroxid e
T ick one box.
/.
ce m e nt D D escribe how you would carry o ut this
limeston e D titration. [3]
quicklime D
{Total: 10]
(Cambridge /GCSE Chemistry 0620 Paper 21
D Q5 November 201 O)
slaked lime
[] 29 Amm o nia is an important industrial chemi cal.
1
a (i) Give th e electron stru cture of an ato m o f
c Som e farm ers use calcium hyd roxide to contro l
soil acidity. n i tr o g e n. [l ]
( i) Wh y is it impo rtant to co ntro l soil (ii ) U se this elect roni c structure, rather than
acidi ty? [ 1] the valency o f nitrogen, to explain wh y th e
(ii ) Acid rain can cau se soil to become acidic. fo rmula o f amm onia is NH3 no t NH4. [2]
b Ammo nia is mad e b y th e H aber P rocess.
D escribe how acid rain is fo rm ed. [3]
N2(g) + 3H2(g) c= 2NH3(g)
d Calcium hydroxide reacts with hydrochloric acid .
fo rward reaction is exothermic
calcium hyd rox ide + hyd rochl o ric acid ---,.
calcium chlo rid e + water The percentage of ammonia in th e equilibrium
mixture varies with conditio ns.
(i) State the name of this type of chemical
reactio n. [l ] Press ure /atmospheres 100 200 300 400
% ammon iaat300 °C 45 65 72 78
(ii ) A dilute solutio n o f calcium hyd roxide can % ammon ia at soo •c
18 25 31
be titrated with hyd rochlo ri c acid using the
apparatus sh own. The conditio ns actually used arc
20 0 atmosph eres, 450 °C and an iron catalyst.
(i) The orig inal catalyst was platinum. Suggest
a reason why it was chan ged to iron. [ 1]
(ii) Explain why th e hig hest pressure g ives
the hig hest percentage o f ammo nia in the
equilibrium mixture. [2 ]
REVISION AND EXAM-STYLE QUESTIONS
(iii) What happens to the unrcactcd nitrogen 31 C h oose an clem ent which fits each o f the
and hydrogen? [ 1] fo llowing d escriptio ns.
( iv) State o ne advantage and one disadvantage ( i) lt is a yellow solid which b urns to fo rm
o f using a lower temperature. [2] an acidic oxide. [l ]
[Total: 9/ (ii) This clem ent is a black solid which ,
when heated , forms a purple vap our. [ 1]
(Cambridge /GCSE Chemistry 0620 Paper 31 ( iii)Most o f its soluble salts arc blue . [l ]
Q4 November 2010)
( iv) It has a basic oxide o f the t yp e M O
which is u sed to treat acidic soils. [ 1]
30 Lead is a grey metal. (v) It is an unrcactivc gas u sed to fill
a State two physical properties which arc balloon s. [l]
ch aracteristic o f metals. [2] [Total: 5/
b To which Group in the Perio dic Table d ocs (Cambridge /GCSE Chemistry 0620 Paper 31
lead belo ng? [ 1] Q1 June2010)
c An isotope o f lead has the m ass number 20 8 .
Complete the table to sh ow the number o f 32 This questio n is about som e compound s o f
nitrogen.
subatomic particles in an ato m o f this isotope A mixture o f ammo nium sul fa tc and sodium
hyd roxide was warm ed in a test-tube. The gas was
of lead. Use the Perio dic Table to help you. tested with m oist red litmus pap er.
Typ e of particle Number of particles
electrons
protons
[3] ~ red litmus paper
d When lead is hC'.1.tcd in O.\)'gcn, lead(n) o xide is
formed. Write a word equation for this reaction. [ 1]
e When lcad(n) oxide is heated with carbo n, lead
and carbo n m o noxide arc fo rmed.
PbO + C -Pb + CO
( i) W hich substance becom es oxidised during
this reaction ? [ 1] i
(ii) C arbo n m o noxide is a cova lent co mpo und. heat gently
W hich o n e o f th ese statem en ts ab out
carbo n m o n oxid e is correct? a State th e name o f the gas released. [l ]
Tick one box. b State th e colo ur ch an ge o f the litmus paper. [ 1]
DIt is a solid with a high melting po int. c Complete the word equatio n fo r the reacti o n o f
amm onium carbo nate with hyd rochl oric acid .
It conducts electricity when it is D amm o nium + hydrochlo ric ---> _ + _ + _
a liquid.
D ca r b on a t e acid [3]
It is a gas at room temperature. D
d Ammo nium salts su ch as amm o nium nitrate,
It fo rms ab o ut 1% o f the atmosphere.
N H 4N03, and ammo nium chlo rid e, NH 4C l,
arc used as fe rtilisers.
[l ] (i) E xplain why farm ers need to u se
[Total: 9/
(Cambridge /GCSE Chemistf'f 0620 Paper 22 fe rtilisers. [l]
Q6June2010) (ii) Explain wh y ammo nium nitrate is a better
fe rtiliser than ammo nium chlo ride. [ 1]
( iii) Calculate the relative fo rmula m ass o f
ammonium nitrate. [l ]
Theory
e When ammonium nitrate is heated nitrogen(!) 35 a Su lfuric acid is made by the Contact process.
oxide is given off.
Nitrogen (!) oxide relights a glowing splint.
Name one other gas which relights a glowing This is carried out in the presence of a catalyst
splint. [l ] at 450 °C and 2 atmospheres pressure.
f State one harmful effect of nitrogen oxides on (i) H ow is the sulfur dioxide made? [l ]
the environment. [ 1] (ii) Give another use of sulfur dioxide. [l ]
(rota/: tO/ (iii)Namc the catalyst used. [l ]
(Cambridge /GCSE Chemistry 0620 Paper 02 (iv) If the temperature is decreased to 300°C,
04 June 2009) the yield of sulfur trioxide increases.
Explain why this lower temperature
33 a The major gases in unpolluted air arc 79% is not used. [l ]
nitrogen and 20% oxygen. (v) Su lfur trioxide is dissolved in concentrated
(i) Name another gaseous ckmcnt in sulfuric acid. This is added to water to
unpolluted air. [ 1] make more sulfuric acid. Why is su lfur
(ii) Name two compounds in unpolluted trioxide not added directly to water? [ 1]
~r. [2] b Sulfuric acid was first made in the Middle
b Two common pollutants in air arc carbon East by heating the mineral grccnvitriol,
monoxide and the oxides of nitrogen. FcS04 .7H20. The gases formed were cooled.
(i) Name another pollutant in air. [ 1] FeS04.7H20 (s) - FcS04 (s) + 7 H20(g)
(ii) Describe how carbon monoxide is green crystals yel low powder
formed. [2]
(iii) H ow arc the oxides ofnitrogen formcd?[2] 2FcS04(s) - Fe20 3(s) + S02(g) + S03(g)
(iv) Explain how a catalytic converter reduces On cooling
the emission of these two gases. [2]
[Total: 10] S03 + H 20 __, H 2S04 sulfuric acid
(Cambridge /GCSE Chemistry 0620 Paper 31 S02 + H 20 __, H 2S03 sulfu rous acid
01 November 2009)
(i) H ow could you show that the first reaction
34 Oxides are classified as acidic, basic, neutral and is reversible? [2]
amphoteric.
a Complete the tabk. (ii) Su lfurous acid is a rcductant. What
would you sec when acidified potassium
Typ e of oxide pH of solution oxide Ex.ample manganatc(vn) is added to a solution
acidic
containing this acid? [2]
basic
(iii)Suggcst an explanation for why sulfurous
neutral
acid in contact with air changes into
sulfuric acid. [1]
[6] c 9. 12 g of anhydrous iron(n) sulfatc was heated.
b (i) Explain the term amphoteric. [l ] Calculate the mass ofiron(m) oxide formed
(ii) Name two reagents that an: needed to and the volume ofsulfur trioxide, at r.t.p.,
show that an oxide is amphoteric. [2] formed.
(rota/: 9/ 2FcS04(s) - Fe20,(s) + S02(g) + S03(g)
(Cambridge /GCSE Chemistry 0620 Paper 31
02 November 2009) mass of one mok ofFcS04 = 152g
number of moles of FcS04 used= _ _
number of moles of Fe20 3 formed = _ _
mass of one mok ofFc20 3 = _ _ g
REVISION AND EXAM-STYLE QUESTIONS
m ass o fi ro n( m ) oxide fo rmed= _ _ g 3 7 Sele nium and sulfur arc in G roup Vl . They have
number o f m oles o f S03 fo rm ed = _ _ similar p roperties .
volume of sulfur trioxid e fo rmed = dm 3 a O ne o f the main u ses o f selenium is in
[6] pho t oelectric cells. Th ese cells can ch ange lig ht
(rota/: 16/ into electrical e n ergy.
(Cambridge /GCSE Chemistf'f 0620 Paper 31 (i) N am e a process w hich can cha nge light
Q6 November 2009) into che mical e ne rgy.
(ii) Nam e a d evice w hich can chan ge ch emical
36 The diagram shows a wate r tn:atmc nt works. e ne rgy into electrical e ne rgy. [2]
aluminium sulfate b The elect ron distributio n o f a sele nium ato m is
adde d
2+8+ 18 +6.
(i) Selenium forms an io ni c compo und w ith
potassium. Draw a diagram w hich sh ows
th e fo rmula o f this io ni c compo und , the
charges o n the io ns and the arran gem ent o f
sand filter th e valen cy electro ns around th e negative
io n.
a St ate o n e use o f wate r in industry. [ 1J Use o to represent a n electron fr om an
b Explain how th e sand filter helps puri f)1 the ato m o f potassium .
wate r. [2] Use x to represent an electro n fro m an
c The aluminium ions in aluminium sulfatc ca use ato m o f sele nium. [3]
clay particles to clump t ogethe r. (ii) Draw a diagram sh owing the arrangem ent
D escri be a test fo r aluminium io ns. o f the valen cy electro ns in on e m o lecule o f
t es t th e covale nt compo und selenium chlorid e.
result [3] Use x to represent an electro n fro m an
d Why is chlorin e added to th e water? [ 1] at o m o f sele nium.
e Chl orine is in Group Vl I o f the Perio di c Table . Use o to represent a n elec tron fr om an
W hen chlorine reacts with a solution o f ato m o f chlorine. [3]
potassium bromide, the solution turns a (iii) Predic t two diff"ere n ces in the physical
reddi sh- b rown colo ur. properties o f these two compo und s. [2]
(i) Write a word equ ation fo r this reaction. [2 ] c The sclcnide io n react s w ith wate r.
(ii) E xplain why io dine d ocs no t react w ith a Se2- + H 20----, H Se- + OH-
so lutio n o f po tassium bromid e. [ 1] W ha t type o f reagent is th e sd e nide io n in this
f W he n chl o rine reacts w ith sodium to fo rm reactio n ? Give a reason for your ch o ice. [3]
sodium chl oride, energy is released. [Total: 13]
(i) State the name given to a reactio n which (Cambridge /GCSE Chemistry 0620 Paper 31
releases e n ergy. [ 1] Q2 June2011)
(ii) W hat t yp e o f bonding is present in sodium
chlo ride? [ 1] 38 C hlorine reacts w ith phospho rus to fo rm
phospho rus trichloride.
(iii) E xplain w hat happen s in t e rms o f elect ron a Draw a diagram sh owing the arrangem ent o f
th e valency elect rons in o ne m o lecule o f the
transfer w h en a sodium ato m reacts with a covalent compo und, phospho ru s tri chlo ride.
Use x to represent an electro n fro m a
chlo rine ato m. [2 ] phospho rus ato m .
(rota/: 14/
(Cambridge /GCSE Chemistf'f 0620 Paper 02
Q4 June 2008)
Theory
U se o to represent an electro n fr o m a chlo rine 40 O zone is a fo rm o f oxygen. Ozone is p resent in
ato m. [2] the upper atmosphere and it p reven ts dangerous
b Ph osphorus trichloridc reacts with water to solar radiatio n fro m reaching the Earth 's surface.
fo rm two acids. Som e of th e chemicals that d iffu se into the
(i) Balance the equation fo r this reacti o n. upper atmosph ere decompose ozon e. C hemi cals
PCl3 + _ H 20 ---+ _ H Cl+ H 3 P0 3 [l ] that have this effect arc methan e (C H 4 ) ,
chlorom cthanc (C H 3Cl) and an oxid e of
(ii) D escribe h ow you could sh ow th at nitrogen (N02).
(i) Which o f these three ch emica ls di ffuses
phospho ru s acid , H 3 P0 3 , is a weaker acid
th an hyd rochloric acid. [3] the m ost slowly? Give a reason fo r your
(iii) T wo salts of phospho rus acid arc its ch o ice. [2]
sodium salt, which is soluble in water, and (ii) C hl orom cthan c is fo rmed wh en seaweed
its calcium salt which is in soluble in water. decomposes. Name the compounds in the
Su ggest a method o f preparatio n fo r each environment fro m which seaweed might
o f these salts fr o m aq ueous ph osph o rus have o btain ed th e followin g elem ents:
acid . Spccif)1 any o ther reagent need ed and carbo n; _ _
briefl y o utline th e method . hyd rogen; _ _
sodium salt [2] chlo rine. [3]
calcium salt [2] (iii) H ow can chloro mcthan c be m ad e fro m
methan e?
(Total: tO/ reagent _ _
(Cambridge /GCSE Chemistry 0620 Paper 33
conditio n [2]
Ql June2011)
(iv) The oxides o f nitrogen arc atm ospheric
pollutants. Describe how they arc fo rm ed . [2]
39 Steel is an alloy made fro m impure iron . ( v) Com plete the equ ation fo r the
a Both iron and steel ru st. The fo rmula fo r ru st is deco mpositio n of ozone.
Fc20 3.2 H 20 . It is hydrated iron (m ) oxid e. __ o, - __ [2]
(i) N am e the two substances that must be
present fo r ru sting to occur. [2] {Total: 11]
(Cambridge /GCSE Chemistry 0620 Paper 31
(ii) Painting and coating with g rease arc two
Q2 June 201 O)
metho d s o f preventing iron or steel fr om
rusting. Give two o ther m etho d s. [2]
b (i) Na me a reagent that can reduce iron( m ) Organic
oxide to iron . [ 1]
(ii) Write a symbo l equation fo r th e reduction 41 Ethcn c, C2H 4, is m anL1 fach1rcd by cracking
pet roleum fractio ns.
o fi ron ( m ) oxide, Fc20 3 , to iron. [2]
c (i) Calculate the mass o f o ne m o le o f
a (i ) What d o yoll und erstand by the term
Fe20 3 .2H 20. [2] pctro/cu,n fraction? [ 1]
(ii) Use your answer to (i) to calcu late the (ii) Com plete th e equatio n for the
percentage of iron in rust. [2] manufactllrc of cthcnc fr om d o d ecan c,
d Iron fro m the b last forn acc is impure. T wo of C12 H 26·
th e im purities arc carbon and silicon. These C12 H 26 ---+ C2 H 4 + _ _ [I ]
arc rem oved by b lowing oxygen throll gh the
m olten iron and adding calcium ox ide. b T wo fractio ns o btained fro m the d istillation o f
(i) Explain how th e additi o n of oxygen pct ro lellm arc refin ery gas an d gaso line. State
rem oves carbon. [ 1] o ne use o f each o f these fractions. [2]
(ii) Explain how the additio n o f oxygen an d c Ethcnc is an llnsaturatcd h yd rocarbo n. Wh at
calcium oxide rem oves silicon. [2] d o yoll und erstand by the followin g terms?
(Total: t3/ lln sa t u rat c d
(Cambridge /GCSE Chemistry 0620 Paper 31 hyd rocarbon [2]
Q3 November 2008)
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Cambridge IGCSE Chemistry 3rd Edition
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