4 Any gas evolved is passed through the delivery stopped. Otherwise the limewater will be sucked
tube into the limewater. The effect on limewater back into the hot boiling tube.
is recorded (Figure 8.9).
5 When there is no further change, the colour
of the residue when it is hot is recorded. The
colour of the residue when it is cooled to room
temperature is also recorded.
6 Steps 1 to 5 of the experiment is repeated using
other carbonate salts as shown in Table 8.16.
8 Precaution Figure 8.9 Heating test on carbonate salts
Make sure that the end of the delivery tube is
removed from the limewater before heating is
Results
Table 8.16 Heating test on carbonate salts
Carbonate salt Colour of salt Colour of residue Effect on limewater
before heating When hot When cold
Potassium carbonate, K2CO3 White White White No visible change
Sodium carbonate, Na2CO3 White White White No visible change
Calcium carbonate, CaCO3 White White White Limewater turns milky
Magnesium carbonate, MgCO3 White White White Limewater turns milky
Zinc carbonate, ZnCO3 White Yellow White Limewater turns milky
Lead(II) carbonate, PbCO3 White Brown Yellow Limewater turns milky
Copper(II) carbonate, CuCO3 Green Black Black Limewater turns milky
Discussion 4 Note that if excess carbon dioxide gas is passed
1 In this experiment, limewater is used to test for the into the limewater, the white precipitate, CaCO3
formed will dissolve to form calcium hydrogen
presence of carbon dioxide gas. Carbon dioxide carbonate. The limewater will turn clear again.
gas turns limewater milky because calcium
carbonate is formed as a white precipitate. CaCO3(s) + H2O(l) + CO2(g) → Ca(HCO3)2(aq)
CO2(g) + Ca(OH)2(aq) → CaCO3(s) + H2O(l) white precipitate colourless solution
2 When zinc carbonate is heated, zinc oxide and Conclusion
carbon dioxide gas are produced.
1 Potassium carbonate and sodium carbonate will
ZnCO3(s) → ZnO(s) + CO2(g) not decompose on heating.
Zinc oxide is yellow when hot and white when 2 Other metal carbonates decompose on heating to
cooled. produce metal oxides and carbon dioxide gas. A
3 When lead(II) carbonate is heated, lead(II) oxide general equation representing the decomposition
and carbon dioxide gas are produced. of carbonate salt by heat is
PbCO3(s) → PbO(s) + CO2(g) MCO3(s) → MO(s) + CO2(g)
Lead(II) oxide is brown when hot and yellow metal metal
when cooled. carbonate oxide
Salts 244
To study the effect of heat on nitrate salts
Apparatus 4 When there is no further change, the colour of
the residue is recorded when it is hot. The colour
Boiling tubes, litmus paper, test tube holder, wooden of the residue is recorded again when the residue
splint, spatula and Bunsen burner. is cooled to room temperature.
Materials 5 Steps 1 to 4 of the experiment are repeated using
Potassium nitrate, sodium nitrate, magnesium nitrate, other nitrate salts as shown in Table 8.17.
zinc nitrate, aluminium nitrate, lead(II) nitrate and
copper(II) nitrate.
Procedure Figure 8.10 Heating test on nitrate salt Activity 8.8 8
1 One spatula of potassium nitrate is placed in a
dry boiling tube and the colour of the solid is
noted.
2 The nitrate salt is heated slowly and then
strongly.
3 Any gas evolved is tested by a glowing wooden
splint (Figure 8.10(a)) and moist blue litmus
paper (Figure 8.10(b)). The results are recorded.
Table 8.17 Heating test on nitrate salts
Colour of Colour of residue Test on gas
salt before
Nitrate salt When When Colour of Effect on Effect on
heating hot cold gas glowing wooden moist blue
litmus paper
splint
Potassium nitrate, KNO3 White White White Colourless Rekindles No change
Sodium nitrate, NaNO3 White White White Colourless Rekindles No change
Magnesium nitrate, Mg(NO3)2 White White White Brown Rekindles Turns red
Aluminium nitrate, Al(NO3)3 White White White Brown Rekindles Turns red
Zinc nitrate, Zn(NO3)2 White Yellow White Brown Rekindles Turns red
Lead(II) nitrate, Pb(NO3)2 White Brown Yellow Brown Rekindles Turns red
Copper(II) nitrate, Cu(NO3)2 Blue Black Black Brown Rekindles Turns red
Discussion Generally, 2MNO3(s) → 2MNO2(s) + O2(g),
1 The brown gas that changed moist blue litmus metal nitrate metal nitrite
paper to red is nitrogen dioxide gas. where M = K or Na.
2 The gas that rekindles a glowing wooden splint 2 Other metal nitrates decompose to metal oxides,
is oxygen gas. nitrogen dioxide gas and oxygen gas when heated.
A general equation representing the decomposition
Conclusion of other nitrate salts by heat is
1 All nitrate salts decompose on heating.
Potassium nitrate and sodium nitrate decompose 2M(NO3)2(s) → 2MO(s) + 4NO2(g) + O2(g)
metal nitrate metal oxide
to oxygen gas when heated.
245 Salts
Test for carbonate ions, CO32– Test for nitrate ions, NO3–(brown ring test)
1 When dilute acid (hydrochloric acid, nitric 1 When dilute sulphuric acid and iron(II)
acid or sulphuric acid) is added to an sulphate, FeSO4 solution are added to
aqueous carbonate solution (or solid an aqueous nitrate solution, followed by
carbonate), effervescence occurs. concentrated sulphuric acid added slowly
along the side of the test tube, a brown
2 The gas evolved turns limewater milky. Carbon ring is formed in the middle section of the
dioxide gas is produced, indicating the solution mixture.
presence of carbonate ions.
2 The formation of the brown ring (a complex)
CO32–(aq) + 2H+(aq) → CO2(g) + H2O(l) indicates the presence of nitrate ions.
8
Figure 8.11 Acid test for carbonate ions Figure 8.12 Brown ring test for nitrate ions
Tests for the Presence of Anions in Aqueous Solutions SPM
’05/P2
Q8
The presence of anions, CO32–, NO3–, SO42–, and Cl– can be identified
by conducting specific tests on the aqueous salt solution.
Test for sulphate ions, SO42– SPM Test for chloride ions, Cl–
’10/P2 1 When dilute nitric acid is added to an
aqueous chloride solution followed by silver
1 When dilute hydrochloric acid (or nitric nitrate solution, AgNO3, a white precipitate
is formed.
acid) is added to an aqueous sulphate
2 The white precipitate is silver chloride,
solution followed by barium chloride AgCl.
solution, BaCl2 (or barium nitrate solution, Ag+(aq) + Cl–(aq) → AgCl(s)
Ba(NO3)2), a white precipitate is formed.
2 The white precipitate is barium sulphate, 3 AgNO3 solution provides the Ag+ ions
to react with the Cl– ions to produce the
BaSO4. insoluble AgCl salt.
Ba2+(aq) + SO42–(aq) → BaSO4(s)
3 BaNO3 or BaCl2 solution provide the Ba2+
ions to react with the SO42– ions to produce
the insoluble BaSO4 salt.
H2SO4 followed by Ba(NO3)2 or BaCl2 solution is not HCl followed by AgNO3 solution is not a suitable test
a suitable test for the presence of SO42– ions. This is for the presence of Cl– ions. This is because the Cl–
because the SO42– ions in H2SO4 will give a positive ions in HCl will give a positive test with AgNO3 solution.
test with Ba(NO3)2 or BaCl2 solution.
Salts 246
To test for the presence of anions in aqueous salt solution
Apparatus sulphate solution, 2 mol dm–3 hydrochloric acid and
nitric acid, concentrated sulphuric acid and 0.1 mol
Test tubes, delivery tube with rubber stopper, spatula, dm–3 silver nitrate solution.
test tube holder and Bunsen burner.
Materials Procedure
1 mol dm–3 sodium carbonate solution, sodium The steps to test the aqueous salt solutions as planned
chloride solution, sodium sulphate solution, sodium in Table 8.18 are carried out. The observations and
nitrate solution, barium chloride solution and iron(II) inferences are tabulated.
Results Activity 8.9 8
Table 8.18 Tests for the presence of anions in aqueous salt solutions
Test Observation Inference
1 (a) About 2 cm3 of sodium carbonate solution is Effervescence occurs. A gas is evolved.
placed in a test tube.
Limewater becomes Carbon dioxide gas is evolved.
(b) About 2 cm3 of dilute hydrochloric acid is milky. Carbonate ion, CO32–, is
added to the carbonate solution. present.
(c) Any gas produced is bubbled into lime- A white precipitate is Chloride ion, Cl–, is
water.
produced. present.
2 (a) About 2 cm3 of sodium chloride solution is
placed in a test tube. A white precipitate is Sulphate ion, SO42–, is present.
produced.
(b) About 2 cm3 of dilute nitric acid is added to
the chloride solution followed by about A brown ring is formed Nitrate ion, NO3–, is
2 cm3 of silver nitrate solution. in the middle of the present.
solution.
3 (a) About 2 cm3 of sodium sulphate solution is
placed in a test tube.
(b) About 2 cm3 of dilute nitric acid is added to
the sulphate solution followed by about
2 cm3 of barium chloride solution.
4 (a) About 2 cm3 of sodium nitrate solution is
placed in a test tube.
(b) About 2 cm3 of dilute sulphuric acid is added
to the nitrate solution followed by about
2 cm3 of iron(II) sulphate solution. The
mixture is shaken to mix well.
(c) Concentrated sulphuric acid is added care
fully to the mixture along the wall of the
tilted test tube without shaking the mixture.
Conclusion 3 The presence of sulphate ions can be identified
by the addition of barium chloride solution to
1 The presence of carbonate ions can be identified by an acidified solution when a white precipitate is
the addition of a dilute acid where carbon dioxide produced.
gas evolved will turn the limewater milky.
4 The presence of nitrate ions can be identified by
2 The presence of chloride ions can be identified by the brown ring test.
the addition of silver nitrate solution to an acidified
solution when a white precipitate is produced.
247 Salts
Tests for Cations Observation Formula of Cation
metal hydroxide present
1 The cations usually tested are: Al3+, Pb2+, Zn2+,
Brown precipitate Fe(OH)3 Fe3+
Mg2+, Ca2+, Fe3+, Fe2+, Cu2+ and NH4+ ions.
2 An aqueous solution of the cation is prepared White precipitate Al(OH)3, Pb(OH)2, Al3+, Pb2+,
by Zn(OH)2, Mg(OH)2, Zn2+, Mg2+,
(a) dissolving the salt in water (if the salt is Ca(OH)2 Ca2+
soluble in water). No precipitate – Na+, K+,
(b) dissolving the salt in dilute acid and then
NH4+
filtering (if the salt is insoluble in water).
8 The filtrate contains the cation. Some metal hydroxides are soluble in excess
3 The aqueous cation solution is then tested sodium hydroxide or aqueous ammonia to
form complexes.
with 6 Al3+, Pb2+ and Zn2+ ions form metal hydroxides
(a) sodium hydroxide solution, NaOH, which are white precipitates that are soluble
((bc)) aaqsupeeocuifsicamremagoennitaassoaluctoionnfi,rmNHat3o(rayqt)e,st. in excess sodium hydroxide. Furthermore,
4 Sodium hydroxide and aqueous ammonia zinc hydroxide is also soluble in excess
supply hydroxide ions, OH– to produce metal aqueous ammonia.
hydroxide as precipitate with cation solutions 7 Mg2+ and Ca2+ ions form metal hydroxides
which are white precipitates with sodium
except Na+, K+ and NH4+ ions. hydroxide, but only Mg2+ ions will produce
white precipitate with aqueous ammonia.
Generally, Mn+(aq) + nOH–(aq) → M(OH)n(s) 8 Ammonium ion, NH4+ does not produce any
precipitate with sodium hydroxide or aqueous
precipitate ammonia. However, if a mixture of ammonium
ion and sodium hydroxide is heated, ammonia
Example: Pb2+(aq) + 2OH–(aq) → Pb(OH)2(s) gas is produced.
Al3+(aq) + 3OH–(aq) → Al(OH)3(s)
NH4+(aq) + OH–(aq) → NH3(g) + H2O(l)
5 Transition element cations produce specific
coloured metal hydroxide, whereas the other
cations produce white precipitate as shown in
Table 8.19.
Table 8.19 Colours of metal hydroxides SPM 9 All three Cu(OH)2, Fe(OH)2 and Fe(OH)3 do not
dissolve in excess sodium hydroxide solution.
’11/P1 However, Cu(OH)2 (a blue precipitate)
dissolves in excess aqueous ammonia to
Observation Formula of Cation form a dark blue solution.
metal hydroxide present
10 A summary of the sodium hydroxide tests and
Blue precipitate Cu(OH)2 Cu2+
Fe(OH)2 Fe2+ aqueous ammonia tests for cations are shown
Dirty green
precipitate in Table 8.20.
Table 8.20 Hydroxide tests for cations SPM
’10/P1
Cation A little sodium Excess sodium hydroxide, A little aqueous Excess aqueous ammonia,
hydroxide, NaOH(aq) NaOH(aq) ammonia, NH3(aq) NH3(aq)
NH4+ No precipitate forms. Ngaosperveoclivpeistawtehfeonrmhesa. tNedH3 No precipitate No precipitate forms
NH3 gas evolves when forms
heated
Pb2+ White precipitate White precipitate soluble in White precipitate White precipitate insoluble in
Zn2+ White precipitate excess NaOH excess NH3(aq)
Al3+ White precipitate
White precipitate soluble in White precipitate White precipitate soluble in
excess NaOH excess NH3(aq)
White precipitate soluble in White precipitate White precipitate insoluble in
excess NaOH excess NH3(aq)
Salts 248
Cation A little sodium Excess sodium hydroxide, A little aqueous Excess aqueous ammonia,
hydroxide, NaOH(aq) NaOH(aq)
ammonia, NH3(aq) NH3(aq)
White precipitate insoluble
Mg2+ White precipitate in excess NaOH White precipitate White precipitate insoluble in
White precipitate insoluble excess NH3(aq)
in excess NaOH
Ca2+ White precipitate No precipitate No precipitate forms
forms
Cu2+ Blue precipitate Blue precipitate insoluble in Blue precipitate Blue precipitate soluble in
excess NaOH dexacrekssbNluHe 3s(oalqu)titoonform a
Fe2+ Dirty green precipitate Dirty green precipitate Dirty green Dirty green precipitate
insoluble in excess NaOH precipitate insoluble in excess NH3(aq) 8
Fe3+ Brown precipitate Brown precipitate insoluble Brown precipitate Brown precipitate insoluble
in excess NaOH in excess NH3(aq)
Confirmatory tests for Fe2+, Fe3+,NH4+ and SPM (a) an iodide solution (e.g. KI), produces a
Pb2+ ions ’11/P1 yellow precipitate of PbI2.
1 Potassium hexacyanoferrate(II), K4Fe(CN)6 (b) a chloride solution (e.g. NaCl), produces
solution, potassium hexacyanoferrate(III), a white precipitate of PbCl2.
K3Fe(CN)6 solution and potassium (c) a sulphate solution (e.g. H2SO4),
thiocyanate, KSCN, solution can be used to 4 iBoodtihdper,oledaPudbc(IeI2Is)aarcewhhlsoiotreliudpber,leecPipibniCtalht2eoaotnfwdPabtlSeeOrad4a.(nIId)
confirm the presence of Fe2+ and Fe3+ ions. recrystallise when cooled.
5 Nessler reagent is a special reagent to test
The observation is shown in Table 8.21.
the presence of ammonium ion. This reagent
2 Fe2+ ions can also be confirmed by acidified forms a brown precipitate with ammonium
potassium manganate(VII), KMnO4 solution. ion.
If a few drops of KMnO4 solution acidified by 6 A summary of the confirmatory tests for Pb2+,
dpiulurpteleHc2oSOlo4uarreofadthdeedmtoanagsaonlauttei(oVnI,I)aniodnthies
NH4+, Fe2+ and Fe3+ ions is shown in Table
decolourise d, then the solution contains Fe2+ 8.21.
ions.
3 Pb2+ ions can be confirmed by adding
Table 8.21 Confirmatory tests for Pb2+, NH4+, Fe2+ and Fe3+ ions
Cation Specific reagent Observation
KI, NaI Yellow precipitate, soluble in hot water
and recrystallises when cooled
Lead(II) ions, Pb2+ KCl, NaCl, HCl White precipitate, soluble in hot water
and recrystallises when cooled
K2SO4, Na2SO4, H2SO4 White precipitate, insoluble in hot water
Ammonium ions, NH4+ Nessler reagent Brown precipitate
Light blue precipitate
Iron(II) ions, Fe2+ Potassium hexacyanoferrate(II), K4Fe(CN)6 Prussian blue (dark blue) precipitate
Potassium hexacyanoferrate(III), K3Fe(CN)6 Purple colour decolourises
Blood red colour
Acidified KMnO4 Turnbull’s blue (dark blue) precipitate
Greenish-brown solution
Iron(III) ions, Fe3+ Potassium thioc yanate, KSCN
Potassium hexacyanoferrate(II), K4Fe(CN)6
Potassium hexacyanoferrate(III), K3Fe(CN)6
249 Salts
Flowchart for the analysis of cations in salts
Unknown cation solution
Test 1: Add NaOH(aq) solution
8 White precipitate Coloured precipitate No precipitate
Zn2+, Al3+, Pb2+, Ca2+, Mg2+ Blue Green Brown NH4+
Cu2+ Fe2+ Fe3+
Add excess On heating
NaOH(aq) solution Cation solution
Gas turns red litmus
Precipitate Precipitate does not Test 2: Add aqueous to blue. NH3 gas
dissolves dissolve NH3 evolves.
NH4+
Zn2+, Al3+, Pb2+ Ca2+, Mg2+ Coloured precipitate
Blue Green Brown
Cation solution Cation solution Cu2+ Fe2+ Fe3+
Test 2: Add excess Test 2: Add excess
aqueous NH3 aqueous NH3
Add Cation solution
White White White No excess Cation
precipitate precipitate precipitate precipitate aqueous solution Test 2 Add Nessler
dissolves insoluble is formed NH3 reagent
in excess in excess Ca2+ Test 3: Add
NH3 NH3 Mg2+ present KSCN Brown
present precipitate
Zn2+ Al3+ or Dark blue Blood red
present Pb2+ solution colour
Cu2+ present Fe3+ present NH4+
present
Cation solution Cation solution
Test 3: Add KI Test 3: Add K3Fe(CN)6
Dark blue precipitate
No Yellow
precipitate precipitate Fe2+ present
Al3+ present Pb2+ present
Salts
250
Flowchart for the analysis of anions in salts
Unknown solid anion
Test 1: Heating the solid
Gas evolves and turns Gas rekindles glowing wooden Gas evolves and No gas evolves
limewater milky. splint and a brown gas is decolourises acidified SO42– or Cl–
CO2 gas is evolved. evolved.
O2 and NO2 gas evolve. KMnO4 solution.
CO32– ion SO2 or SO3 evolves.
NO3– ion
SO42– ion
8
Solid salt or salt Anion solution Anion solution Anion solution
solution
Test 2 Add FeSO4, dilute Test 2 Add Test 2 Add
Test 2 Add dilute H2SO4 and then HNO3 and HNO3 and
acid concentrated H2SO4 Ba(NO3)2 Ba(NO3)2
slowly
Gas evolves and turns
limewater milky. Brown ring White precipitate No precipitate.
CO2 evolves. SO42– ion is not
present.
CO32– ion
present NO3– ion SO42– ion
present present
Anion solution
Test 3 Add
HNO3
and
AgNO3
White precipitate
Cl– ion present
Qualitative Analysis to Identify the Ions Present in a Salt
1 Two types of salt analysis: compounds. Carry out chemical tests
SPM (A) To confirm the cation and anion present to identify the anion and cation in
’09/P2 in a named salt solid Y and solution Z.
2 An example of problem A, to confirm the
Example Compound X is lead(II) carbonate. cation and anion in compound X, is shown
How do you carry out tests to confirm in Activity 8.10 To confirm the cation, Pb2+ ions
the cation and anion in compound X? and the anion, CO32– ions in compound X.
3 An example of problem B, a planned analysis,
(B) To identify the cation and anion present is shown in Activity 8.11 To identify the cations
in an unknown salt and anions in unknown salt Y and salt Z.
Example You are supplied with solid Y and
solution Z. Both Y and Z are ionic
251 Salts
To confirm the cation, Pb2+ ions and the anion, CO32– ions in
compound X
Apparatus Procedure
Test tubes, boiling tube, test tube holder, delivery
tube with stopper, spatula and Bunsen burner. 1 The steps in the experiment which are supplied
in Table 8.22 are carried out.
Materials
Solid lead(II) carbonate, 2 mol dm–3 nitric acid, 2 The observations are recorded and inferences are
2 mol dm–3 sodium hydroxide solution, limewater made.
and 0.5 mol dm–3 potassium iodide solution.
3 Care is taken to ensure that all test tubes and
spatula are clean to prevent contamination.
Activity 8.10 & 8.11 Results
8
Table 8.22
Experiment Observation Inference
1 (a) A spatula of compound X is heated in a
The residue is brown when Lead(II) oxide is formed.
boiling tube, gently at first and then strongly. hot and yellow when cold. Pb2+ ions may be present.
(b) The gas produced is passed into limew ater
The gas evolved turns lime- Carbon dioxide gas is evolved.
in a test tube using a delivery tube.
2 5 cm3 of dilute nitric acid is added to a quarter water milky. CO32– ions may be present.
spatula of compound X in a test tube. The gas The gas evolved turns lime- Carbon dioxide gas is
evolved is tested with limewater.
3 The mixture in step 2 is filtered. The filtrate water milky. evolved. CO32– ions are
which contains the cation is divided into two confirmed to be present.
portions in two test tubes.
(a) For the first portion, sodium hydroxide A white precipitate is produ Pb2+, Al3+ or Zn2+ ions may be
solution is added gradually until in excess. ced which is soluble in present.
(b) For the second portion, a little potassium excess sodium hydroxide
iodide solution is added.
solution.
(i) A little distilled water is added to the
mixture and then heated. A yellow precipitate is Lead(II) iodide may be
produced. formed.
(ii) The mixture is allowed to cool under
running water. The yellow precipitate The yellow precipitate is
dissolves in hot water to lead(II) iodide.
form a colourless solution.
Upon cooling, golden yellow Lead(II) ions, Pb2+ is
crystals are reformed. confirmed to be present.
Conclusion
It is confirmed that compound X contains lead(II) ions and carbonate ions.
To identify the cations and anions in unknown salt Y and
salt Z
Apparatus Materials
Test tubes, boiling tube, test tube holder, delivery Unknown salt Y and salt Z, 2 mol dm–3 sodium hydroxide
tube with stopper, wooden splint and Bunsen burner. solution, aqueous ammonia, dilute sulphuric
acid, dilute nitric acid, dilute hydrochloric acid,
concentrated sulphuric acid, silver nitrate solution,
barium chloride solution and iron(II) sulphate
solution.
Salts 252
Procedure
(A) Tests on salt Y
Experiment Observation Inference
1 Salt Y is heated strongly.
A brown gas is produced. Nitrogen dioxide gas and
2 The residue formed is cooled and then A gas that rekindles a oxygen gas are produced.
dissolved in dilute nitric acid. The resulting glowing wooden splint is Nitrate ion, NO3– is
solution is divided into 3 portions. also produced. A white present.
(a) Sodium hydroxide solution is added to the residue is formed.
first portion of solution Y until in excess. The solution contains
The white residue cations.
(b) Aqueous ammonia is added to the second dissolves in nitric acid.
portion of solution Y until in excess.
8
(c) Potassium iodide solution is added to the
third portion of solution Y. White precipitate that Pb2+, Al3+ or Zn2+ ions may
dissolves in excess sodium be present.
3 Salt Y is dissolved in distilled water. A little hydroxide is formed.
iron(II) sulphate and dilute sulphuric acid is Zn2+ ions are not present.
added to solution Y. Concentrated sulphuric White precipitate that Pb2+ ions or Al3+ ions may
acid is then added slowly along the side of the does not dissolve in excess be present.
test tube to the mixture. aqueous ammonia is formed.
Pb2+ ions are not present.
No noticeable change. Al3+ ions are present.
A brown ring is formed. NO3– ions are present.
(B) Tests on salt Z
Experiment Observation Inference
1 Salt Z is dissolved in distilled water. The Z dissolves in water. Z is a soluble salt.
Mg2+ ions or Ca2+ ions may
solution is divided into 4 portions. A white precipitate that be present.
2 Sodium hydroxide solution is added to the first does not dissolve in excess Mg2+ ions are present.
sodium hydroxide is formed.
portion of solution Z until in excess. A white precipitate that SO42– ions are not present.
does not dissolve in excess
3 Aqueous ammonia is added to the second aqueous ammonia is Cl– ions are present.
portion of solution Z until in excess. formed.
No noticeable change.
4 Dilute hydrochloric acid is added to the third
portion of solution Z followed by barium A white precipitate is
chloride solution. formed.
5 Dilute nitric acid is added to the fourth portion
of solution Z followed by silver nitrate solution.
Conclusion
Compound Y contains Al3+ ion and NO3– ion.
Compound Z contains Mg2+ ion and Cl– ion.
253 Salts
In qualitative analysis of unknown ions, you should not test for the ions present in the reagents used in
analysis. For example, if the salt is dissolved in dilute hydrochloric acid, do not test for the presence of chloride
ion. In the same way, if aqueous ammonia is added to the salt solution, do not test for ammonium ion.
1 Pb(NO3)2 solution produces insoluble salts as solution is added to Cl– ions solution followed by
ptioernsetsc.ifpoiHrtaetthenecewp, irtehPsbe(CnNOcOe323–o)2f iosnoslu, tiSoOn42i–s ions and Cl– an acid, a white precipitate that is insoluble in acids
not a good
types of will be formed.
the above three 3 Ba(NO3)2 or BaCl2 solutions produce insoluble salts
with both CO32– ions and SO42– ions. However,
8 ions. However, a negative test may indicate the BaCO3 is soluble in acids. Hence, the formation
of white precipitate with Ba2+ ions solution in
2 AprgeNsOen3cesoolfuNtioOn3– ions. insoluble salts with
produces the presence of acids confirms the presence of
both CO32– ions and Cl– ions. However, Ag2CO3 SsoOlu42t–ioinonfso.llIof wBead2+ ions solution iswahditdeedprteocipSOita4t2e–
is soluble in acids. Hence, the formation of white by an acid, a
precipitate with AgNO3 solution in the presence of that is insoluble in acids will be formed.
acids confirms the presence of Cl– ions. If AgNO3
6 ’05
Describe chemical tests that can be used to verify the • Add 2 cm3 of barium nitrate solution to 5 cm3 of
cations and anions in beaker 1 and beaker 2. solution from beaker 1. The formation of a white
precipitate will verify the presence of sulphate
Comments ions.
• Add a little sodium carbonate powder to 5 cm3 of
• Add 1 cm3 of Nessler reagent to 5 cm3 of solution
solution from beaker 1. The evolution of a gas that from beaker 2. The formation of a brown precipitate
turns limewater milky will verify the presence of will verify the presence of ammonium ions.
hydrogen ions in the acid.
• Add a little of iron(II) sulphate and dilute sulphuric
acid to 5 cm3 of solution from beaker 2, followed
by concentrated sulphuric acid added slowly. The
formation of a brown ring will verify the presence
of nitrate ions.
8.2 2 Solid Y is not soluble in water but dissolves in dilute
nitric acid and gives out a gas that turns limewater
1 The formulae of a few salts are given below: milky. The solution produced is yellow in colour and
forms a brown precipitate when sodium hydroxide
CPbuCCll22,, CZunCSOO43,, MFeg((NNOO33))32,, CZnuC(NOO3,3)N2a2CO3, Al2(SO4)3, solution is added.
(a) Give the name of salt Y.
Which of the above salts (b) Write an equation for the reaction between salt
(a) is a solid that is insoluble in water? Y and dilute nitric acid.
(b) is a white solid? (c) Predict the reaction that would occur when salt
(c) is soluble in water to produce a blue solution? Y is heated strongly.
(d) forms a white precipitate with barium chloride (d) Predict the observation that will occur when
potassium thiocyanate solution is added to the
that is insoluble in acid? yellow solution produced from the addition of
(e) forms a white precipitate that dissolves in nitric acid to salt Y.
sodium hydroxide solution?
(f) forms a white precipitate with aqueous ammonia
but is not soluble in excess aqueous ammonia?
Salts 254
(e) Write an equation for the formation of the brown 4 You are given three types of acids: sulphuric acid,
precipitate when sodium hydroxide solution is nitric acid and hydrochloric acid. Using suitable
added to an acidic solution of salt Y. chemical tests, describe briefly how you can identify
the three types of acids.
3 Dilute nitric acid is added to aqueous solutions of
unknown salts P, Q and R respectively. It is found 5 You are given three types of salts: zinc nitrate, lead(II)
that solutions P and Q do not show any noticeable nitrate and calcium nitrate. Using suitable chemical
change, whereas effervescence occurs in solution tests, describe briefly how you can differentiate
R. The gas that is evolved from solution R turns between the three types of salts.
limewater milky. When silver nitrate solution is
added to solution P, a white precipitate is formed. 6 An experiment was carried out to identify the cation
When barium nitrate is added to solution Q, a white and anion present in an unknown salt Z. The tests
precipitate is produced. Identify the anions that are and observations are tabulated below. Fill in the
present in solutions P, Q and R. correct inferences in the table and deduce the
cation and anion present in salt Z.
8
Test Observation Inference
1 NaOH solution is added gradually to a little Z A white precipitate which is soluble in excess
solution until in excess. NaOH is produced.
2 sAoqluuetioounsuNntHil3 is added gradually to a little Z A white precipitate which is soluble in excess
in excess. aqueous NH3 is produced.
3 Solid Z is heated slowly and then strongly. A brown gas and a gas that rekindles a glowing
wooden splint are produced. The residue formed
4 Dilute nitric acid followed by BaCl2 solution is is yellow when hot and white when cooled.
added to a little Z solution.
No noticeable change occurs.
8.3 Practising Systematic and Meticulous Methods when Carrying
Out Activities
1 Correct methods in preparing salt crystals of the test tube towards yourself or
(a) A salt solution is evaporated until towards your fellow students.
saturated so that solid salt may be (c) Gases such as sulphur dioxide, nitrogen
crystallised. The salt is not heated until dioxide, chlorine, hydrogen chloride and
dry to prevent decomposition of the salt. ammonia are poisonous. Use suitable
(b) The salt crystals formed are removed by quantities as instructed. Do not use excess
filtration and then rinsed with distilled chemicals. This will cause wastage of
water to remove any foreign ions present chemicals and require a longer time to
in the salt. carry out the experiment. Making accurate
observations will be difficult. Handle all
2 Correct methods in salt analysis apparatus and chemicals carefully in the
(a) All observations must be recorded carefully laboratory.
and immediately after every test. The (d) Addition of a reagent to a salt solution should
inferences are then recorded as soon as be carried out drop by drop while shaking the
possible. test tube until no further change occurs.
(b) During heating, do not direct the mouth
255 Salts
1 A salt is an ionic compound that is formed when 3 Filtration can be used to separate an insoluble
the hydrogen ion in an acid is replaced by a salt (as the residue) from a soluble salt (as the
2 metal ion or ammonium ion (NH4 +). on the filtrate).
The solubility of a salt in water depends 4 The methods of preparing salts depend on the
types of cations and anions present. solubility of salts.
5 Insoluble salts can be prepared by double
8 Type of salt Solubility in water
Sodium, potassium and All are soluble decomposition reaction. Two aqueous solutions
ammonium and nitrate
salts All are soluble except containing the cations and the anions are mixed
Chloride salts PbCl2, AgCl and HgCl
All are soluble except together. The precipitate is then obtained by
Sulphate salts PbSO4, BaSO4 and CaSO4 filtration.
All are insoluble except 6 The mole ratio of ions that react to form a salt
Carbonate salts N(NaHC4O)23C, KO23CO3 and
can be determined from an experiment through the
continuous variation method.
7 Qualitative analysis of salt is a scheme of tests
carried out to identify the cation and anion present
in the salt.
8
Multiple-choice Questions
8.1 Salts 4 Which is the best method to 7 Which of the following pairs of
prepare ammonium nitrate? solutions when added together
1 Which of the following salts is A Double decomposition will produce a precipitate?
insoluble in water? B Neutralisation between an
A Lead(II) nitrate acid and an alkali I Potassium carbonate and
B Calcium chloride C Reaction between an acid silver nitrate
C Magnesium carbonate and a metal
D Iron(III) sulphate D Reaction between an acid II Lead(II) nitrate and sodium
and a metal carbonate chromate(VI)
2 Which of the following
chemicals is most suitable to 5 A sample of zinc(II) sulphate III Sodium carbonate and
bought contained some impurities. copper(II) sulphate
’06 react with HCl to prepare AgCl? The impure salt can be purified
A Silver carbonate by a process known as IV Sodium sulphate and
B Silver nitrate A distillation potassium carbonate
C Silver metal B evaporation
D Silver oxide C crystallisation A I and II only
D recrystallisation B II and III only
3 Which following chemicals C I, II and III only
can be added to nitric acid to 6 Which of the following salts D I, III and IV only
prepare copper(II) nitrate? can be prepared by double 8 Which of the following
A Copper metal decomposition reaction? equations represent a double
B Copper(II) carbonate A Lead(II) nitrate decomposition reaction?
C Copper(II) chloride B Aluminium sulphate IIIIII MBBCC→aaaagSCCSM(OOlON2g(44O3Ca(((saOq3s))q))32)+(+(+sa+)2qHHH+C)22SOS+C2OOl2(NN(44ag(a(aqa)aN2)qqC+O))O3H→→3((2aOaqq)()l)
D Copper(II) sulphate C Silver chloride
D Sodium sulphate
Salts 256
IV 24ZNnO(2N(Og)3)+2(Os)2(→g)2ZnO(s) + B Nitric acid and barium III HCl
A I and II only C II and III only
B I and III only D II and IV only chloride solution IV BaCl2 III only
C Nitric acid and silver nitrate A I and
solution B II and IV only
D Sodium hydroxide solution
9 If 20 cm3 of 0.5 mol dm–3 C I, II and III only
aqueous sodium chloride solution 14 Aluminium sulphate solution D I, III and IV only
is added to 20 cm3 of 1.0 mol and zinc sulphate solution can 16 Solution M reacts with sodium
dm–3 silver nitrate solution, which be differentiated by the hydroxide solution to form a
A addition of silver nitrate solution.
of the following ions are present B addition of aqueous ammonia. white precipitate that is insoluble
C addition of sodium hydroxide
in the solution produced? in excess sodium hydroxide
solution.
I Na+ IIVII CNlO– 3– D addition of barium chloride solution.
II Ag+ Solution M most probably contains
solution.
A I and III only I lead ion
B II and III only II calcium ion 8
C I, II and III only 15 When lead(II) nitrate solution III aluminium ion
D I, II and IV only is added to solution X, a white IV magnesium ion
A II and III only
10 4.2 g of magnesium carbonate precipitate is produced. Solution B I and III only
C II and IV only
reacts with excess hydrochloric X may be D I, III and IV only
acid to produce a salt. Which of III HH2NSOO34
the following are true about the
reaction? [1 mol of gas occupies 17 A student wants to identify cation X that is present in a salt solution. When
ammonia solution is added into the salt solution, a green precipitate is
24 dm3 at room temperature and
’11 formed.
pressure. Relative atomic mass: What is the next test that is needed and the expected observation to
C, 12; O, 16; Mg, 24; Cl, 35.5] confirm cation X?
I Neutralisation reaction takes Test Observation
place. A Add potassium iodide solution Yellow precipitate is formed
II 1.2 dm3 of gas is released. B Add potassium thiocyanate solution Blood red colour is formed
III Mass of salt formed is 4.75 g. C Add potassium hexacyanoferrate(II) Light blue precipitate is formed
solution
IV 4.2 mol of water is formed.
A I and II only
B III and IV only
C II and III only
D I and IV only
D Add Nessler reagent Brown precipitate is formed
8.2 Qualitative Analysis of 18 When a gas Z is passed into copper(II) sulphate solution, a blue precipitate is
Salts
produced. Gas Z may be
11 When solid X is heated strongly,
a gas that turns limewater milky A ammonia C hydrogen chloride
is produced, leaving a white
residue. Which of the following B chlorine D sulphur dioxide
may be solid X?
A Lead(II) carbonate 19 When aqueous iron(III) chloride solution is added to reagent X, a blood
B Sodium carbonate
C Zinc carbonate red colour is produced. Reagent X may be
D Magnesium carbonate
A ammonium sulphite C potassium thiocyanate
12 Which of the following salts will
produce a brown gas on heating? B potassium iodide D potassium hexacyanoferrate(II)
A Lead(II) bromide
B Ammonium nitrate 20 Hydrochloric acid can be differentiated from sulphuric acid by adding
C Potassium nitrate
D Zinc nitrate I barium nitrate III silver nitrate
13 Which of the following is used II barium hydroxide IV sodium carbonate
to test for sulphate ions?
A Iron(II) sulphate solution and A III only C II and IV only
concentrated sulphuric acid
B I and II only D I, II and III only
21 When lead(II) nitrate is heated strongly in a test tube, the following can be
observed.
I A brown gas is evolved.
II A gas that rekindles a glowing wooden splint is evolved.
III A gas that changes moist blue litmus to red is evolved.
IV A white residue is formed.
257 Salts
A I and II only Solution X may be B A white precipitate, which
B III and IV only I sodium hydroxide dissolves in excess ammonia,
C I, II and III only II aqueous ammonia is formed when aqueous
D I, II, III and IV III Nessler reagent ammonia is added.
IV iron(III) nitrate
8 22 Which of the following ions will C A white precipitate is formed
A I and II only when lead(II) nitrate solution
form a precipitate that dissolves B III and IV only is added.
C I and IV only
in excess aqueous ammonia? D I, II and III only D A white precipitate is formed
when silver nitrate solution is
I Copper(II) ions 26 When solid X is heated strongly, a added.
brown gas that turned moist blue
II Aluminium ions litmus paper to red is evolved and 29 When solution X is added to
a black residue is formed. Which sodium chloride solution, a
III Lead(II) ions of the following may be solid X? white precipitate is formed. The
A Copper(II) oxide precipitate dissolves when it
IV Zinc ions B Sodium nitrate is heated with a little distilled
A I and IV only C Copper(II) nitrate water. Which of the following
B II and III only D Magnesium nitrate will be observed when solution
C II and IV only X is added to a solution of
D II, III and IV only 27 Lead(II) nitrate solution and sodium iodide solution?
aluminium sulphate solution can A A white precipitate is formed.
23 Excess powdered carbonate of be distinguished respectively by B A yellow precipitate is
adding formed.
metal Z is added to sulphuric acid C A brown solution is formed.
I sodium hydroxide solution D A purple solution is formed.
and stirred. After a few minutes, II potassium sulphate solution
III barium nitrate solution 30 Which of the following reagents
a light green solution is formed. IV sodium iodide solution can be used to differentiate Fe2+
ions from Fe3+ ions?
Z could be a carbonate of A I and III only
B II and III only I Potassium iodide solution
A iron(II) C copper(II) C II and IV only II Potassium thiocyanate
D III and IV only
B iron(III) D lead(II) solution
28 Which of the following III Potassium
24 Which of the following reagents observations is true for both
sodium chloride solution and hexacyanoferrate(III) solution
can be used to differentiate zinc sulphate solution? IV Potassium manganate(VII)
A A white precipitate is formed
between sodium nitrate and when barium nitrate solution solution
is added. A I and II only
potassium sulphate? B III and IV only
C I, II and III only
I Lead(II) nitrate solution D II, III and IV only
II Barium chloride solution
III Silver nitrate solution
IV Sodium hydroxide solution
A I and II only
B I and III only
C II and IV only
D I and IV only
25 When solution X is added to
iron(III) sulphate solution, a
brown precipitate is produced.
Structured Questions
1 Diagram 1 is a flowchart showing a series of reactions starting from lead(II) oxide.
Lead(II) oxide
sodium substance A
hydroxide
Precipitate F Lead(II) nitrate heat Gas B + Gas C + Solid D
potassium iodide
Precipitate E
Diagram 1 [1 mark]
[1 mark]
(a) (i) Name substance A that is used to react with lead(II) oxide to produce lead(II) nitrate.
(ii) Write a chemical equation for the reaction that takes place in (i).
Salts 258
(b) Gas B is a brown gas while gas C is colourless. [2 marks]
(i) Identify gas B and solid D. [1 mark]
(ii) Suggest a test that you can use to test the presence of gas C. [1 mark]
(c) (i) Name precipitate E. What is the colour of precipitate E? [2 marks]
(ii) Write the ionic equation for the formation of precipitate E. [1 mark]
(d) (i) Name precipitate F. [1 mark]
(ii) Predict the observation that will occur if excess sodium hydroxide is added to precipitate F.
[1 mark]
(e) Name another chemical that can replace lead(II) oxide to react with substance A to produce lead(II)
nitrate.
2 Diagram 2 is a flowchart showing a series of reactions starting from magnesium oxide.
Excess magnesium oxide 8
+
Nitric acid
stir and filter
Filtrate Residue A
Process 1: evaporate, cool and filter Process 2: heated strongly
Crystal B Solid C + Gas D + Gas E
Diagram 2
(a) Write a chemical equation showing the reaction between magnesium oxide and nitric acid. [1 mark]
(b) If 50 cm3 of 2.0 mol dm–3 nitric acid is added to excess magnesium oxide, calculate the maximum mass of
salt that can be produced. [Relative atomic mass: H, 1; N, 14; O, 16; Mg, 24] [3 marks]
(c) The filtrate formed from the reaction above is colourless.
(i) Predict what will be observed if aqueous sodium hydroxide is added to the filtrate gradually until
in excess. [2 marks]
(ii) Name crystal B. [1 mark]
(d) In Process 2, the gas D produced is colourless while gas E is brown.
(i) Identify gas E and name solid C. [2 marks]
(ii) Suggest a test that you can use to test the presence of gas D. [1 mark]
3 The flowchart of Diagram 3 shows a series of reactions I to IV carried out to identify the ions present in compound A.
Diagram 3 [1 mark]
(a) (i) Identify gas C. [1 mark]
(ii) What is the anion present in compound A?
[1 mark]
(b) Based on the observation obtained in reaction III and reaction IV, predict the cation present in [1 mark]
compound A. [1 mark]
[1 mark]
(c) Based on (a) and (b), write a balanced equation for the action of heat on compound A. [1 mark]
(d) Predict the colour of residue B when it is hot and when it is cooled.
(e) (i) Write a balanced equation for the formation of solution D in reaction II. Salts
(ii) State an observation that can be noted in reaction II.
259
(f) (i) Name the white precipitate F formed in reaction IV. [1 mark]
(ii) Write an ionic equation for the formation of the white precipitate F. [1 mark]
(g) Predict the observation that can be obtained when aqueous sodium hydroxide solution is added until [1 mark]
in excess to solution E.
4 Diagram 4 shows the steps involved in the preparation of zinc carbonate.
Zinc oxide Step 1 Salt solution P Step 2 Zinc carbonate
add hydrochloric acid add solution Q
Diagram 4
8 (a) Write a balanced equation for the formation of salt solution P. [1 mark]
(b) Explain briefly how you can obtain a solution of salt P. [2 marks]
(c) (i) Name solution Q that is required to be added to salt solution P in Step 2 to produce zinc
[1 mark]
carbonate. [1 mark]
(ii) Name the type of reaction involved in Step 2. [1 mark]
(iii) Write an ionic equation for the formation of zinc carbonate.
[2 marks]
(d) 30 cm3 of 2.0 mol dm–3 hydrochloric acid is reacted with excess zinc oxide. [2 marks]
[Relative atomic mass: C, 12; O, 16; Zn, 65] [1 mark]
(i) Calculate the number of moles of salt P that is formed.
(ii) Calculate the maximum mass of zinc carbonate that is produced.
(e) Suggest how you would convert zinc carbonate back to zinc oxide.
5 The flowchart in Diagram 5 shows the result of a qualitative analysis that is carried out on a mixture of metal Q and a
water soluble salt P.
Salt P add NaOH and heat Gas R
Salt P Process A add HNO3 + BaCl2 White precipitate S
+
Metal Q add HCl Gas T + Solution U
metal Q
Diagram 5 [1 mark]
(a) Name the process A that is used to separate salt P and metal Q. [2 marks]
(b) Gas R is a gas that can change red litmus paper to blue. Name gas R. Consequently what is the [2 marks]
cation present in solution P?
(c) Name the white precipitate S. What is the anion present in solution P? [1 mark]
(d) When gas R is passed into solution U, a white precipitate is first formed but dissolves when [2 marks]
excess gas R is passed through. Identify the cation present in solution U.
(e) From your answer in (d), determine the identity of metal Q and gas T.
Essay Questions
1 (a) The following are three examples of salts that can Test Procedure Observation
be prepared in the laboratory.
’07 ••• (LMSi)eoa adgFdinur(oemIIms)iuscumthhllpoenhrsiieadtrteaee,t,exPNa,bmaMC2plSg2l(OeNs4O, i3d)2entify the soluble I Heating of salt X solid A brown gas is given
off and a residue that
is brown when hot,
yellow when cooled is
and insoluble salts. [3 marks] formed.
(ii) State the reactants for the preparation of II Add excess aqueous A white precipitate
the insoluble salt in (i). [3 marks] sodium hydroxide which is soluble in
(b) With the aid of a labelled diagram, explain the solution to salt X excess sodium hydroxide
crystallisation method for preparing a soluble salt solution until in excess solution is formed.
from its unsaturated solution. [6 marks]
(c) Table 1 shows the observations from tests carried Table 1
out on salt X.
Salts 260
Based on the information in Table 1: Describe a laboratory experiment to prepare the
(i) Identify an anion that is present in Test I salt. In your description, include the chemical
and describe a chemical test to verify the equations involved. [8 marks]
anion. [4 marks] (c) Three beakers with solutions labelled X, Y and Z
(ii) Identify three cations that are present in may contain the following salt solutions:
Test II. Describe a chemical test to verify the • Zinc sulphate
• Zinc nitrate
cation present in salt X based on Test I and • Magnesium sulphate
Test II. [5 marks]
2 (a) What is meant by a salt? [2 marks] You are provided only with ammonia and barium
nitrate solutions. Describe how you could differentiate
(b) You are required to prepare a sample of dry between the 3 salt solutions by using the two
reagents provided. Include your observations and
lead(II) carbonate salt. The following chemicals conclusions.
are supplied: [10 marks]
• Sodium carbonate solution 8
• Dilute nitric acid
• Lead metal powder
Experiment
’013 ytBheaelrloiupwmrepcinrpeiittcraaiptteeitapstroeolduwutioictehnd, thBbeay(tfNhoOerm3r)eu2alacatniBodnaCabrqeOutw4e.oeAuesnst5puo.d0teacnsmstiuh3maosf chromate(VI), eKx2pCerOrim4 esnotluttoiomn ereasauctretotheprhoediugchet a
carried out an of
0.50 mol dm–3 aqueous barium nitrate solution
and aqueous potassium chromate(VI) solution of unknown concentration at different volumes. The data
of the experiment obtained is shown in Table 1.
Test tubes Volume of barium nitrate Volume of potassium Height of precipitate (cm)
solution (cm3) chromate(VI) solution (cm3)
1 0.5
2 5.0 1.0 1.0
3 5.0 2.0 1.4
4 5.0 3.0 1.9
5 5.0 4.0 2.4
6 5.0 5.0 2.4
7 5.0 6.0 2.4
5.0 7.0
Table 1
(a) Suggest a suitable apparatus that can be used to (ii) Calculate the number of moles of barium
ions that is used in this experiment.
measure the volume of barium nitrate solution
[3 marks]
and potassium chromate(VI) solution in this
experiment. [3 marks] (e) Based on the formula of the yellow precipitate
(b) State the manipulated variable, responding given, calculate the number of moles of
variable and constant variable in this experiment.
chromate(VI) ions used in the volume in (d)
[3 marks]
(i). Hence calculate the molarity of the aqueous
(c) Draw a graph of the height of the precipitate against potassium chromate(VI), K2CrO4, solution used in
the volume of potassium chromate(VI) solution. this experiment. [3 marks]
[3 marks] (f) Explain why the height of the precipitate does
(d) (i) What is the minimum volume of potassium not change when 5.0 cm3, 6.0 cm3 and 7.0 cm3
chromate(VI) solution required to react
completely with 5.0 cm3 of 0.5 mol dm–3 of potassium chromate(VI) solution is added to
barium nitrate solution?
5.0 cm3 of 0.5 mol dm–3 barium nitrate solution
in Table 1. [3 marks]
261 Salts
9CHAPTER FORM 4
THEME: Production and Management of Manufactured Chemicals
Manufactured Substances
in Industry
SPM Topical Analysis
Year 2008 2009 2010 2011
Paper 1 2 31 2 31 2 31 2 3
Section ABC ABC ABC ABC
Number of questions 3 1 – – – 2 1 – – – 5 – – – – 3 – 1 – –
ONCEPT MAP
MANUFACTURED SUBSTANCES IN INDUSTRY
Sulphuric acid Ammonia Alloys
Uses: To make fertilisers, Uses: To make fertilisers, nitric Purposes:
polymers, detergents, pigments acid and as a cooling agent • To increase hardness and
Manufactured by the Contact (refrigerant)
process: Manufactured by the Haber strength
• Temperature: 450–550 °C process: • To prevent corrosion
• Pressure: 1 atmosphere • Temperature: 450–550 °C • To improve the appearance
• Catalyst: V2O5 • Pressure: 200–500 Examples: Steel, bronze, brass,
magnalium, pewter
atmospheres
• Catalyst: Iron
Synthetic polymers Glass and ceramics Composite materials
Examples and uses: Uses: Construction materials, Examples:
• Polythene: To make plastic household items, laboratory • Reinforced concrete
apparatus • Superconductor
bags, plastic containers and Types of glass: • Fibre optic
toys. • Fused glass • Fibreglass
• Polypropene: To make plastic • Soda glass • Photochromic glass
bottles, tables and chairs • Borosilicate glass
• PVC: To make water pipes, • Lead glass
raincoats and wire casing
9.1 Sulphuric Acid 2 Sulphuric acid, H2SO4 is a non-volatile
diprotic acid.
1 The manufacture of sulphuric acid is one of
the most important chemical industries at the 3 Concentrated sulphuric acid is a viscous
present time.
colourless liquid.
Manufacture of fertilisers
1 Calcium dihydrogen phosphate (super H2SO4 + 2NH3 → (NH4)2SO4 9
ammonium sulphate
phosphate) is prepared from the reaction
between sulphuric acid and tricalcium
phosphate:
2H2SO4 + Ca3(PO4)2 → Ca(H2PO4)2 + 2CaSO4 3 Potassium sulphate is prepared from
the reaction between sulphuric acid and
calcium dihydrogen potassium hydroxide.
phosphate
H2SO4 + 2KOH → K2SO4 + 2H2O
2 Ammonium sulphate is prepared from the
reaction between sulphuric acid and aqueous potassium
ammonia. sulphate
Manufacture of The Uses of Sulphuric Manufacture of
detergents (synthetic Acid in Daily Life white pigment
cleaning agents) in paint barium
Manufacture of In school laboratories sulphate, BaSO4
Sulphuric acid reacts synthetic fibres
with hydrocarbon to 1 As a strong acid The neutralisation
produce sulphonic (polymers) 2 As a drying or between sulphuric
acid. Sulphonic acid acid and barium
is then neutralised Rayon is an example dehydrating agent hydroxide produces
with sodium of a synthetic fibre 3 As an oxidising agent barium sulphate.
hydroxide to produce that is produced from 4 As a sulphonating
the detergent. the action of sulphuric
acid on cellulose. agent
5 As a catalyst
The Industrial Process in the SPM sulphur or metal sulphide
Manufacture of Sulphuric Acid burned in air
’07/P2
sulphur dioxide, SO2
1 Sulphuric acid is manufactured by the Contact (i) V2O5 as the catalyst
process in industry. (ii) temperature of 450 °C – 550 °C
( iii) pressure of 1 atmosphere
2 The raw materials used in the Contact process
are sulphur (or sulphide minerals), air and sulphur trioxide, SO3
water. dissolved in concentrated H2SO4
3 The flowchart of the Contact process is shown oleum, H2S2O7
diluted with equal volume of H2O
in Figure 9.1. It describes how sulphur or
concentrated sulphuric acid, H2SO4
metal sulphide is converted to concentrated
Figure 9.1 Flowchart of the Contact process
sulphuric acid, H2SO4 through regulated steps
in the process. Manufactured Substances in Industry
263
The Contact process involves three stages SPM
’04/P2
sulphur ⎯I→ sulphur dioxide ⎯II→ sulphur trioxide III sulphuric acid
⎯→
Figure 9.2 shows the three stages in the manufacture of sulphuric acid by the Contact process in industry.
9
Figure 9.2 The production of
concentrated sulphuric
acid in industry.
Stage I Stage II SPM
Production of sulphur dioxide gas, SO2
This can be done by two methods: ’09/P1
1 Burning of sulphur in dry air in the
Conversion of sulphur dioxide to sulphur
furnace. trioxide, SO3
S + O2 → SO2 1 The sulphur dioxide gas is dried and
2 Burning of metal sulphide such as zinc purified before being added to dry air to
sulphide or iron(III) sulphide in dry air.
2ZnS + 3O2 → 2SO2 + 2ZnO produce sulphur trioxide gas. This is
(a) to remove water vapour in the air (the
The production of sulphuric acid is known as the
Contact process because the molecules of sulphur reaction of water with SO3 will produce
dioxide, SO2 and oxygen, O2 are in contact with the heat that will vaporise the acid),
catalyst, V2O5. (b) to remove contaminants such as arsenic
The use of V2O5 has replaced the use of platinum as
a catalyst because compounds (found in the sulphur or
(a) platinum is much more expensive,
(b) platinum is easily poisoned (lose its catalyst effect) sulphide minerals) that will poison the
by arsenic compounds. catalyst and make it ineffective.
2 Pure and dry sulphur dioxide with excess
dry oxygen (from air) are passed through a
converter.
3 A high percentage (98%) of sulphur dioxide
is converted into suphur trioxide under the
following conditions:
(i) The presence of vanadium(V) oxide,
V2O5, as a catalyst
(ii) A temperature of between 450°C –
550°C
( iii) A pressure of one atmosphere
2SO2 + O2 2SO3
Manufactured Substances in Industry 264
Stage III The burning of fossil fuels causes 9
environmental pollution, producing
Production of sulphuric acid air pollutants such as carbon
1 In the absorber, sulphur trioxide is dissolved in concentrated monoxide, nitrogen monoxide,
nitrogen dioxide and sulphur
sulphuric acid to produce oleum, H2S2O7, a viscous liquid. dioxide. Scientists are searching for
alternative sources of energy to
SO3 + H2SO4 → H2S2O7 replace fossil fuels. Other than wind
energy, solar energy, geothermal
2 Oleum is then diluted with an equal volume of water to energy (energy from earth’s
produce concentrated sulphuric acid (98%). internal heat) and nuclear energy,
scientists are also researching into
H2S2O7 + H2O → 2H2SO4 the production of fuels from natural
products such as palm oil.
3 The two reactions in stage III are equivalent to adding
sulphur trioxide to water.
SO3 + H2O → H2SO4
However, sulphur trioxide is not dissolved directly in water
to produce sulphuric acid. This is because
(a) SO3 has a low solubility in water.
(b) SO3 reacts violently in water, producing a large
amount of heat which will vapourise sulphuric acid
to form acid mist. The mist is corrosive, pollutes the
air and is difficult to condense.
Environmental Pollution by Sulphur Dioxide
1 Sulphur dioxide is the intermediate product SO2 + H2O ⎯⎯→ H2SO3
of the Contact process. 2SO2 + O2 + 2H2O ⎯⎯→ 2H2SO4
2 Sulphur dioxide is also produced during
8 The effects of acid rain are as follows:
volcanic eruptions. (a) Corrodes concrete buildings and metal
3 However, the main source of sulphur dioxide structures
(b) Destroys trees and plants in forest
is from the burning of fossil fuels such as (c) Decreases the pH of the soil which
becomes acidic, unsuitable for growth
petroleum. Most of the fossil fuels contain of plants and destroys the roots of plants
(d) Reacts with minerals in the soil to
some sulphur. Hence sulphur dioxide is produce salts which are leached out
of the top soil; essential nutrients for
produced when fossil fuels are burned. plants growth are depleted (plants die
4 Waste gases from factories and extraction of of malnutrition and diseases)
(e) Acid rain flows into lakes and rivers.
metal from their sulphide ores also release This increases the acidity of water
and may kill fish and other aquatic
sulphur dioxide into the atmosphere. living things.
5 The burning of products manufactured
9 Two methods to reduce sulphur dioxide
from sulphuric acid such as rayon will also from the atmosphere:
(a) Use low sulphur fuels to reduce the
produce sulphur dioxide gas. emission of sulphur dioxide in exhaust
6 Sulphur is a poisonous and acidic gas that gases.
(b) Remove sulphur dioxide from waste air
can cause environmental pollution. Inhaling by treating it with calcium carbonate
before it is released.
sulphur dioxide affects the respiratory system.
It can cause lung problems such as coughing,
chest pains, shortness of breath and
bronchitis.
7 Sulphur dioxide gas dissolves in
atmospheric water to produce sulphurous
acid, H2SO3 and sulphuric acid, H2SO4.
The presence of these acids in rain water
causes acid rain.
265 Manufactured Substances in Industry
Manufacture by Contact The industrial synthesis of sulphuric acid is
process: represented by the flowchart.
(a) Name this process.
•• 2TeSmOp2 e+raOtu2re: 4502S°CO3– 550 °C (b) Name gas X, gas Y and liquid Z.
(c) Write balanced equations for Step 1 and Step
• Pressure : 1 atm
2.
• Catalyst : V2O5 (d) State the optimum conditions involved in Step
Uses of Sulphuric Pollution by SO2: 2.
sulphuric acid: acid • Forms acid (e) Why is gas Y not dissolved in water to produce
9 • Making paint rain sulphuric acid?
pigments, detergents • Causes breathing 9.2 Ammonia and Its Salts
and fertilisers
problems and 1 Ammonia, NH3 is a very important compound
• As an electrolyte in industry.
lung diseases
in accumulators 2 The main uses of ammonia:
(a) To manufacture nitrogenous fertilisers such
9.1 as ammonium sulphate, ammonium
nitrate and urea
1 An important use of sulphuric acid is in the (b) The liquid form is used as a cooling agent
production of fertilisers. (refrigerant) in refrigerators
(a) Name the fertilisers produced and write the (c) as a raw material for the manufacture of
equations involved when sulphuric acid reacts nitric acid in the Ostwald process
with (d) to be converted into nitric acid used for
making explosives
(i) aqueous ammonia (e) as an alkali to prevent the coagulation
(ii) potassium hydroxide of latex so that latex can remain in the
liquid form
(b) Barium sulphate, BaSO4, is a white pigment (f) to produce ammonium chloride used as
in paint. Write an equation for the formation an electrolyte in dry cells
of barium sulphate from the reaction between (g) as a cleaning agent to remove grease
sulphuric acid and barium hydroxide. (h) used in the manufacture of synthetic fibres
such as nylon
2 Give three uses of sulphuric acid in daily life.
3 The manufacture of nitrogenous fertilisers:
3 Concentrated sulphuric acid can be used as a SPM (a) Ammonium sulphate
dehydrating agent. ’07/P2 Ammonia reacts with sulphuric acid by
(a) What is the function of a dehydrating agent?
(b) When concentrated sulphuric acid is added to neutralisation to produce ammonium
glucose, C6H12O6, a black residue is formed sulphate.
after a few minutes.
2NH3 + H2SO4 ⎯⎯→ (NH4)2SO4
(i) What is the black residue?
(ii) Write a balanced equation for the reaction ammonium sulphate
that has taken place. (b) Ammonium nitrate
Ammonia reacts with nitric acid by
4 Sulphur neutralisation to produce ammonium
nitrate.
+ step 1 Gas X step 2 Gas Y
heating NH3 + HNO3 ⎯⎯→ NH4NO3
Oxygen dilute with ammonium nitrate
Sulphuric acid
water Liquid Z
Manufactured Substances in Industry 266
(c) Urea NH3 + H2O NH4+ + OH–
Ammonia reacts with carbon dioxide at
a temperature of 200 °C and a pressure of 4 As ammonia is very soluble in water, an
200 atmospheres to produce urea. inverted filter funnel is used to prevent the
suction of water (Figure 9.3).
2NH3 + CO2 ⎯→ (NH2) 2CO + H2O
urea 9
4 Liquid ammonia is suitable for use as a cooling Figure 9.3 To dissolve ammonia gas in water
agent (refrigerant) in refrigerators because it
has a low boiling point and is very volatile. 5 Ammonia gas reacts with hydrogen chloride gas
to form white fumes of ammonium chloride.
5 In the Ostwald process, ammonia is converted (This is used as a test for ammonia gas).
into nitric acid by the following steps:
(a) Ammonia is oxidised to nitrogen monoxide NH3 + HCl ⎯⎯→ NH4Cl
gas in the presence of platinum as the
catalyst. 6 Ammonia is alkaline in property and reacts
with dilute acids in neutralisation to produce
platinum salts. For example:
4NH3 + 5O2 ⎯⎯→ 4NO + 6H2O 2NH3 + H2SO4 → (NH4)2SO4
NH3 + HNO3 → NH4NO3
(b) Nitrogen monoxide is further oxidised to
nitrogen dioxide. 7 Aqueous solutions of ammonia produces OH–
ions to react with metal ions (except Na+ ion,
2NO + O2 ⎯⎯→ 2NO2 K+ ion and Ca2+ ion) forming precipitates of
metal hydroxides.
(c) Nitrogen dioxide is dissolved in water to
produce nitric acid. Fe3+ + 3OH– → Fe(OH)3
brown precipitate
4NO2 + O2 + 2H2O ⎯⎯→ 4HNO3
Mg2+ + 2OH– → Mg(OH)2
6 Nitric acid is used to make explosives such white precipitate
as TNT when nitric acid reacts with organic
substances such as methylbenzene (common
name: toluene).
7 Ammonia can neutralise the organic acids
that are produced by microorganisms in latex.
Thus it is used to maintain latex in the liquid
form.
8 Ammonia reacts with hydrogen chloride to
produce ammonium chloride which is used
as the electrolyte in dry cells.
NH3 + HCl → NH4Cl
The Properties of Ammonia 8 Some metal hydroxides such as zinc hydroxide
and copper(II) hydroxide dissolve in excess
1 Ammonia is a colourless and pungent gas. It aqueous ammonia to form complexes. For
is less dense than air. example:
2 Ammonia changes moist red litmus paper to Zn(OH)2 + 4NH3 → [Zn(NH3)4]2+ + 2OH–
blue. Thus ammonia is an alkaline gas. Cu(OH)2 + 4NH3 → [Cu(NH3)4]2+ + 2OH–
3 Ammonia dissolves in water to produce a weak
alkali. A 0.1 mol dm–3 ammonia solution has
a pH value of about 10.
267 Manufactured Substances in Industry
To investigate the properties of ammonia gas
Activity 9.1 Apparatus 2 The mixture in the test tube is heated. The
9 ammonia gas produced is tested in turn by using
pH paper, red litmus paper, beaker, glass rod, test tubes, (a) a piece of moist red litmus paper,
U-tube with soda lime, beaker and delivery tube. (b) a glass rod dipped in concentrated hydro
chloric acid.
Materials
Ammonium chloride, calcium hydroxide, concen 3 Ammonia gas is collected in inverted test tubes
trated hydrochloric acid, distilled water. using downward displacement of air. The test
tubes are then stoppered immediately.
Procedure
1 A spatula of ammonium chloride and a spatula 4 A little distilled water is added to the test tube of
ammonia gas which is then shaken. The solution
of calcium hydroxide are put in a test tube. The formed is tested with a piece of pH paper.
test tube is then connected to a U-tube with soda
lime as shown in Figure 9.4. 5 A test tube of ammonia is inverted with its
mouth below a beaker of water. The stopper of
the test tube is then removed as shown in Figure
9.5. Observation made is recorded.
Figure 9.4 Preparation of ammonia gas Figure 9.5 Testing the solubility of ammonia
Results in water
Test Observation Inference
1 With moist red litmus paper The red litmus paper changed to a Ammonia gas is alkaline
2 With hydrogen chloride vapour blue colour
White fumes are formed Ammonia gas forms white fumes
3 With pH paper of ammonium chloride with
pH paper changed to a blue colour, hydrogen chloride gas
4 A test tube of ammonia is corresponding to a pH value of Aqueous ammonia is a weak
inverted in a beaker of water about 10 alkali
Water rushes in and fills up the
whole test tube Ammonia gas is very soluble in
water
Discussion (b) The ionic equation for the reaction between
1 Ammonia gas is produced when an ammonium ammonium salt and alkali is
salt such as ammonium chloride is heated with NH4+ + OH– → NH3 + H2O
an alkali such as calcium hydroxide.
(a) The equation for the reaction between 2 Soda lime in the U-tube is used as a drying agent
to dry the ammonia gas produced. In place of soda
ammonium chloride and calcium hydroxide lime, anhydrous calcium oxide can also be used as
is a drying agent. However, concentrated sulphuric
acid cannot be used to dry ammonia gas as it will
2NH4Cl + Ca(OH)2 → CaCl2 + 2NH3 + 2H2O react with ammonia in a neutralisation reaction.
Manufactured Substances in Industry 268
3 Ammonia gas is collected in inverted test tubes Conclusion
using downward displacement of air because
ammonia is less dense than air. 1 Ammonia is an alkaline gas which turns red
litmus paper to blue and dissolves in water to
4 Ammonia gas is very soluble in water. As such it form a weak alkali.
cannot be collected by a downward displacement
of water. 2 Ammonia gas reacts with hydrogen chloride to
form white fumes of ammonium chloride.
5 Ammonia gas reacts with hydrogen chloride to
form white fumes of ammonium chloride. 3 Ammonia gas is very soluble in water.
NH3 + HCl → NH4Cl
The Industrial Process in the 4 In the Haber process: 9
Manufacture of Ammonia SPM (a) A mixture consisting of one volume of
’06/P2 nitrogen gas and three volumes of pure
1 The Haber process is the industrial method
used to prepare ammonia gas on a large scale and dry hydrogen gas is compresssed
using nitrogen gas and hydrogen gas. to a pressure between 200 – 500
atmospheres.
(b) The gas mixture is passed through a
catalyst of powdered iron at a temperature
of 450 – 550 °C.
(c) At this optimum temperature and pressure,
ammonia gas is produced.
N2 + 3H2 2NH3
In 1918, Fritz Haber was awarded the Nobel prize 5 The gas mixture produced consists of about
for his discovery of the ind ustrial manufacture of 17% ammonia gas. The ammonia gas is
ammonia gas from hydrogen gas and nitrogen gas liquefied when the gas mixture is cooled. The
unreacted nitrogen gas and hydrogen gas are
2 Nitrogen gas used in the Haber process is pumped back to the catalytic column to be
obtained from the fractional distillation of reacted again.
liquid air.
Figure 9.6 The manufacture of ammonia gas by the
3 Hydrogen gas used in the Haber process can Haber process
be obtained by two methods:
(a) The reaction between steam and heated
coke (carbon).
H2O + C ⎯⎯→ CO + H2
This mixture is known as water gas
(b) The reaction between steam and natural
gas (consists mainly of methane, CH4).
2H2O + CH4⎯⎯→ CO2 + 4H2
269 Manufactured Substances in Industry
9 SPM (a) Based on the graph, what is the effect of
temperature and pressure on the percentage of
’06/P2 ammonia produced?
Q5
(b) State one problem each that is accompanied
1 The reaction between nitrogen gas and hydrogen with the effects mentioned in (a) when the
gas to produce ammonia gas is a reversible factory wants to increase the percentage of
reaction. This means that not all the nitrogen ammonia produced.
gas will react with hydrogen gas completely. The
optimum temperature and pressure are used to (c) Discuss how the problems in (b) may be
ensure a satisfactory yield of ammonia. overcome by using an optimum temperature
and pressure.
2 The percentage yield of ammonia gas depends on
the temperature and pressure used, as shown in Solution
Figure 9.7 below. (a) Lower temperature will increase the percentage
Figure 9.7 Effects of temperature and pressure of ammonia produced. Higher pressure will
on the yield of ammonia increase the percentage of ammonia produced.
(b) Lower temperature will lower the rate of
(a) The lower the temperature, the higher the reaction. Higher pressure will increase the cost
yield of ammonia. of production.
(c) Using an optimum temperature of 450-550 °C,
(b) The higher the pressure, the higher the yield of the rate of reaction will not be too low and
ammonia. yet produce a high yield of ammonia. Using
an optimum pressure of 200-500 atm, the cost
(c) However, low temperature will lower the rate of increasing the pressure and using stronger
of reaction. High pressure will increase the pipes will not be too high to produce a high
cost of production. yield of ammonia.
(d) Hence, the most suitable temperature and Ammonium Fertilisers
pressure to produce a high yield of ammonia
is a temperature of 450 °C–550 °C and a 1 Plants require nitrogen to produce protein.
pressure of 200–500 atmospheres. Nitrogen is absorbed by plants in the form
of nitrates, NO3– which are soluble in water.
1 ’06
2 Ammonium fertilisers are chemical fertilisers
A factory that is manufacturing ammonia carried added to the soil to replace the elements in
out a test to determine the percentage of ammonia soil used up by plants.
that can be produced at two different conditions: I
and II. The results are shown in the graph below. 3 Ammonium fertilisers contain ammonium
ions, NH4+, that can be converted into nitrate
ions by bacteria living in the soil.
4 The effectiveness of ammonium fertilisers is
determined by the percentage of nitrogen
by mass in them. The fertiliser with a higher
percentage of nitrogen is more effective.
5 The percentage of nitrogen by mass can be
calculated using the following formula:
Percentage of nitrogen by mass
= —M——o—Ml—a—ra—sm—s—ao—sf—sn—oi—tf—rfo—e—gre—tin—li—s—e—r 100%
Manufactured Substances in Industry 270
1 SPM = 2[14 + 4 (1)] + 32 + 4(16) = 132
’10/P1 1 mol (NH4)2SO4 consists of 2 mol atoms of nitrogen.
Percentage of nitrogen in 1 mol of (NH4)2SO4
Calculate the percentage by mass of nitrogen in = —21—(31—24—) 100% = 21.2%
ammonium sulphate, (NH4)2SO4. [Relative atomic
mass: N,14; H.1; S,32; O,16]
Solution
Relative molecular mass of (NH4)2SO4
To prepare ammonium sulphate, (NH4)2SO4, an ammonium
fertiliser
Apparatus 5 The ammonium sulphate crystals are then removed Activity 9.2 9
by filtration, washed with distilled water and
25 cm3 pipette, 50 cm3 burette, dropper, retort stand dried between filter papers.
with clamp and white tile.
Figure 9.8 Titration of sulphuric acid with
Materials ammonia solution
1 mol dm–3 sulphuric acid, 2 mol dm–3 aqueous Discussion
ammonia solution and methyl orange indicator. 1 The equation for the neutralisation of aqueous
Procedure ammonia and sulphuric acid is
(A) To determine the volume of sulphuric acid re 2NH3 + H2SO4 → (NH4)2SO4
quired to neutralise 25 cm3 of ammonia solution 2 The first titration (Experiment A) is carried out to
determine the volume of sulphuric acid required
1 25 cm3 of 2.0 mol dm–3 aqueous ammonia solution to completely neutralise 25 cm3 of aqueous
ammonia.
is transferred using a 25 cm3 pipette to a clean
3 In the second titration (Experiment B), the methyl
conical flask. Three drops of methyl orange orange indicator is not used so that the salt
produced is not contaminated with the indicator.
indicator are added to the alkali and the colour
4 The ammonium sulphate solution produced is
of the solution is noted. not evaporated until dry because ammonium
sulphate solid will decompose when heated.
2 A 50 cm3 burette is filled with sulphuric acid and
5 Usually, the mass of ammonium sulphate crystals
clamped to a retort stand. The initial burette obtained from the experiment is less than the
theoretical value because not all ammonium
3 reading (V1) is recorded. 25 cm3 of the aqueous sulphate crystals can be crystallised from the
The conical flask containing solution. Some ammonium sulphate remains
dissolved in the solution.
ammonia is placed below the burette. A piece of
Conclusion
white tile is placed below the conical flask for clearer Ammonium sulphate, an example of ammonium
fertiliser, can be prepared by the neutralisation reaction
observation of the change in colour (Figure 9.8). between aqueous ammonia and dilute sulphuric acid.
4 Sulphuric acid is added slowly from the burette
to the aqueous ammonia solution in the conical
flask while the flask is gently swirled.
5 Titration is stopped when methyl orange changes
colour from yellow to orange. The final burette
6 Trehaedvinolgum(Ve2)ofissurelpchourrdiecda.cid required to neutralise
25.0 cm3 of ammonia solution is (V2 – V1) cm3.
(B) To prepare ammonium sulphate crystals
1 25 cm3 of 2.0 mol dm–3 aqueous ammonia
solution is pipetted into a clean conical flask.
2 (V2 – V1) cm3 of sulphuric acid is added from the
burette to the aqueous ammonia solution.
3 The mixture in the conical flask is transferred
to a beaker and is slowly evaporated until a
saturated solution is formed.
4 The saturated solution is left to cool. White
crystals of ammonium sulphate are produced.
271 Manufactured Substances in Industry
Ammonium sulphate is an acidic salt. Hence, long term use of ammonium sulphate as a fertiliser will increase the
acidity in the soil. This can be overcome by adding quicklime (calcium oxide) to neutralise the acidic soil.
Manufacture of ammonia: Haber Process
N2(g) + 3H2(g) 2NH3(g)
• Temperature: 450 °C–550 °C • Catalyst: iron powder
• Pressure: 200–500 atm.
9
Uses Ammonia, NH3 Tests
• Manufacture of • Turns moist red litmus paper blue
• Forms white fumes with HCI gas
fertilisers, nitric acid
Properties
Reactions • Colourless • A weak alkali
• Produce ammonium salts with acids • Pungent smell • Very soluble in water
• Produce metal hydroxide as precipitate
9.2
1 Ammonia is commercially produced by the Haber The given diagram shows the production of a
process. fertiliser, ammonium nitrate. Step 2 is known as the
(a) Name the raw materials used in the production Ostwald Process.
of ammonia gas. (a) Name gas A, gas B and acid C in the diagram.
(b) Name the catalyst used in the Haber process. (b) Name the industrial process in the production of
(c) State the optimum temperature and pressure
used for this process. gas B in step 1.
(d) Write a balanced equation for this process. (c) State the source from which gas A is obtained.
(e) State two uses of ammonia in daily life. (d) What will be observed if gas B comes in contact
2 Gas A gas B step 2 acid C with hydrogen chloride gas?
+ step 1 Ostwald process (e) Write a balanced equation for step 3.
H2 (f) Calculate the percentage by mass of nitrogen in
ammonium nitrate. [Relative atomic mass: H,1;
N,14; O,16]
step 3
ammonium nitrate
9.3 Alloys 2 Pure metals are weak and soft because the
arrangement of atoms in pure metals makes
Meaning and Purpose of Making Alloys them ductile and malleable.
1 An alloy is a mixture of two or more 3 Arrangement of pure metal atoms
elements with a certain composition in A pure metal contains atoms of the same size
which the major component is a metal. arranged in a regular and organised closed-
packed structure (Figure 9.9).
Manufactured Substances in Industry 272
Figure 9.9 Arrangement of atoms in a pure metal (b) In an alloy, these atoms of different sizes 9
disrupt the orderly arrangement of the
4 Weakness of pure metal metal atoms and also fill up any empty
(a) Ductility spaces in the metal crystal structure.
Pure metals are soft because the orderly
arrangement of atoms of the same size (c) Hence, the layers of metal atoms are
enables the layers of atoms to slide over prevented from sliding over each other
each other easily when an external force easily. This makes the alloy harder and
is applied on them. This makes the metals stronger, less ductile and less malleable
ductile and metals can be drawn to form than its pure metals.
long wires (Figure 9.10).
Figure 9.12 Arrangement of atoms in alloys
Figure 9.10 Ductility of pure metal 6 The properties of a pure metal are thus improved
(b) Malleability by making them into alloys. There are three
There are imperfections in the natural aims of alloying a pure metal:
arrangement of metal atoms. Empty space (a) To increase the hardness and strength of
exists in the structures of pure metals.
When hammered or pressed, groups a metal
of metal atoms may slide into new (b) To prevent corrosion or rusting
positions in these empty spaces. This (c) To improve the appearance of the metal
makes metals malleable, able to be made
into different shapes or pressed into thin surfaces, with a better finish and lustre
sheets (Figure 9.11).
Aluminium and copper wires can be made
Figure 9.11 Malleability of pure metal because of the ductility of metals
Pure gold is too soft to make jewellery. 916 gold Source: Wikimedia; Rosmaniakos
consiststs of 91.6% gold SPM Golden drinking vessel from Iran was made
5 The making of alloys in about 5 B.C., proving the use of metal
’08/P1, alloys in early civilization
’09/P2,
’11/P2 Pure metals have the following physical properties:
(a) Ductile (can be drawn into a wire)
(a) In the process of alloying, one or more (b) Malleable (can be shaped by hammering)
(c) High melting and boiling points
foreign elements are added to molten metal. (d) High density
(e) Good conductors of electricity
When the alloy hardens, the positions of
some of the metal atoms are replaced by
atoms of foreign elements, with sizes bigger
or smaller than the original metal atoms.
273 Manufactured Substances in Industry
Gold is one of the most ductile and malleable metal. Pure gold is too soft and is not suitable for making any type of
jewellery. Gold is thus usually alloyed with copper, silver or palladium. The carat unit is used to measure the purity of
gold. The carat value is the number of parts of gold in 24 parts of the alloy. Hence, 24-carat gold is pure gold. 18-carat
gold consists of 75% of gold by weight.
Aims of alloying
9
To increase the hardness To prevent corrosion To improve the SPM
and strength appearance ’05/P1
Pure metals such as tin and
Alloying improves the iron are easily corroded in Metals are easily tarnished
hardness and strength of a damp, polluted or acidic because of the formation
metal. air. of metal oxides on the
1 The addition of a little 1 The addition of carbon, metal surfaces. The process
of alloying can maintain
carbon to iron metal nickel and chromium the lustre on the surface of
produces steel which to iron metal produces the metal.
is a very hard alloy of stainless steel. Stainless 1 Stainless steel is more
iron. steel is an alloy which
2 The addition of can resist rusting. The shiny than pure iron.
magnesium to chromium and nickel 2 Adding a little copper
aluminium metal form chromium(III)
produces an alloy called oxide and nickel(IV) and antimony to tin
magnalium. Magnalium oxide which prevents
is harder than the iron from rusting. produces the alloy
aluminium but still 2 The addition of tin to pewter which is harder
retains the low density copper produces bronze and shinier, and not so
of aluminium metal. which is able to resist easily tarnished.
3 The addition of tin to corrosion and tarnish. 3 Alloy wheels made from
copper metal produces aluminium and other
bronze. Bronze is an
alloy harder than both elements improve the
tin and copper.
look of vehicles.
The body of airplanes are made of Stainless steel kitchenware resists
magnalium which is harder than rusting
pure aluminium
Malaysian pewter is suitable
for making shiny and attractive
ornamental objects
Manufactured Substances in Industry 274
9.1
To compare the hardness of a pure metal and its alloy SPM
’05/P3
’04/P2
Problem statement
Are alloys harder than pure metals? Figure 9.13 To compare the hardness of an Experiment 9.1 9
alloy with its pure metal
Hypothesis
Results
Bronze is harder than copper. When a weight is
dropped onto a ball bearing placed on a metal block Metal Diameter of the dent (mm)
made of copper or bronze, a larger dent will be block I II III Average
produced on the softer copper metal block than on
the bronze block. Copper 3.2 3.3 3.2 3.23
Variables Bronze 2.4 2.5 2.5 2.47
(a) Manipulated variable : Types of materials (copper Discussion
or bronze) to make the
metal block 1 The bigger the average diameter of the dents
produced by the steel ball bearing on the metal
(b) Responding variable : Diameter of the dent made means that it has been pressed deeper into the
by a steel ball bearing metal surface.
(c) Constant variable : Size of steel ball bearing, 2 Thus copper is softer than bronze because the
mass of weight used, height steel ball bearing has been pressed deeper into
from which it is dropped the surface of copper metal than that of bronze.
3 Bronze is a type of alloy formed from copper
Materials and tin. The tin atoms are larger than the copper
atoms. They distort the orderly structure of
Copper block, bronze block, ball bearing, 1 kg the copper atoms so that the layers of copper
weight, metre ruler, retort stand with clamp, atoms can no longer slide easily over one
cellophane tape and thread. another. This makes bronze harder than copper.
Procedure
Conclusion
1 A metre ruler is clamped to a retort stand, and
a piece of copper block is placed on the base of 1 The average diameter of the dents made by the
the retort stand. steel ball bearing on the copper block is bigger
than that on the bronze block.
2 A steel ball bearing is placed on the copper
block and a piece of cellophane tape is used to 2 Hence, bronze, a type of alloy, is harder than
hold the ball bearing in place. pure copper metal. The hypothesis is accepted.
3 A 1 kg weight is hung at a height of 50 cm above
the copper block (Figure 9.13).
4 The weight is dropped onto the ball bearing
placed on the copper block.
5 The diameter of the dent made by the ball
bearing is measured.
6 The experiment is repeated three times using
different areas on the surface of the copper
block.
7 The average diameter of the dent is calculated.
8 Steps 1 to 7 are repeated using a piece of bronze
block.
275 Manufactured Substances in Industry
9.2
To compare the rates of rusting of iron, steel and stainless steel SPM
’05/P3
Problem statement Procedure
Experiment 9.2 How do the rates of rusting of iron, steel and stainless 1 Three test tubes are half-filled with jelly solution
9 steel differ? and are labelled as A, B and C.
Hypothesis 2 1 cm3 of potassium hexacyanoferrate(III) solution
Pure iron rusts faster than steel while stainless steel is added to every test tube.
does not rust easily.
3 An iron nail, a steel nail and a stainless steel nail
Variables are polished with sandpaper to remove any rust
(a) Manipulated variable : Types of nails (iron, steel formed. The nails are then placed in the three
test tubes labelled A, B and C respectively.
and stainless steel)
(b) Responding variable : Rate of rusting 4 All three test tubes are allowed to stand for 5
(c) Constant variable : Size of nails, duration of days before they are examined.
rusting and conditions of
experiment (temperature,
supply of water and air)
Materials Figure 9.14 To compare the rates of rusting of
Iron nail, steel nail, stainless steel nail, 5% jelly iron, steel and stainless steel
solution and potassium hexacyanoferrate(III)
solution and sandpaper.
Results
Test tube Type of nail Observation Inference
A Iron nail Blue colour is formed around the nail Rusting occurs
B Steel nail A slight blue colour is formed A little rusting occurs
C Stainless steel nail No blue colour is observed No rusting occurs
Discussion Conclusion
1 When iron rusts, iron(II) ion, Fe2+ is produced.
1 The formation of a blue colour shows that
Fe → Fe2+ + 2e– rusting of iron (corrosion) has occurred.
2 Potassium hexacyanoferrate(III) solution is used 2 The presence of a blue colour shows that iron
to test the presence of iron(II) ion. A dark blue nail rusts easily (corroded), steel nail rusts
colour will be formed. The intensity of the blue slightly and stainless steel does not rust at all.
colour indicates the rate of rusting. The hypothesis is accepted.
3 A stainless steel alloy which resists rusting, is
prod uced by adding nickel and chromium to iron
metal.
Manufactured Substances in Industry 276
The Composition, Properties and Uses of Some Common Alloys SPM
’10/P1,
’11/P1
Alloy Composition Properties Uses
Carbon steel 99% iron Hard and strong • Frameworks of buildings and bridges
Stainless steel 1% carbon • In the making of tools, framework of
Bronze Shiny, strong and
74% iron resists rusting heavy machinery and body of vehicles
Brass 18% chromium
8% nickel Hard, strong and • In the making of cutlery and kitchenware
Magnalium 90% copper shiny • In the making of machine parts and
Duralumin 10% tin
surgical instruments
Pewter 9
Solder • In the making of kitchenware and ships’
Cupro-nickel 70% copper Hard and shiny propellers
30% zinc
• In the making of decorative ornaments,
70% aluminium Light, hard and strong statues and art crafts
30% magnesium Light, hard and strong
• In the making of electrical connectors and
95% aluminium Lustrous and strong musical instruments
3% copper
1% magnesium Hard, shiny and with • In the making of kitchenware and
1% manganese low melting point decorative ornaments
Hard, shiny and
97% tin resists corrosion • In the making of aircraft body frames
3% copper and • In the making of rims of racing car tyres
antimony • In the making of the bodies of aircrafts
and bullet trains
50% tin
50% lead • In the making of racing bicycles, fan
blades, light electrical cable
copper, nickel
(percentage according • In the making of mugs, candlesticks,
to colour) decorative ornaments and souvenirs
• In the making of solder for electrical wires
and metal pipes
• To make coins of 10 sen, 20 sen, 50 sen
Malaysian coins are made An alloy is a mixture of two or more elements in
from cupro-nickel alloy which the major component is a metal.
(75% Cu, 25% Ni)
(a) Name the elements used to make the alloy
9.3 pewter.
1 Steel and stainless steel are two examples of iron (b) What are the advantages of pewter compared
to its pure metal?
alloys.
(c) State a use of pewter.
(a) What is an alloy? 3 Copper is one of the metals used since ancient times.
(b) What is the element that is added to iron to (a) Explain why copper alloys are more commonly
used than its pure form.
form
(b) Name two examples of copper alloys.
(i) steel? (ii) stainless steel? (c) Pure copper is ductile and malleable. Explain this
(c) Draw the arrangement of particles in property in terms of the arrangements of atoms.
(i) pure iron (ii) steel
(d) Explain why stainless steel and not iron is used
to make cutlery.
2 Pewter is an important alloy made in Malaysia.
277 Manufactured Substances in Industry
9.4 Synthetic Polymers 3 Protein is formed by the polymerisation of
monomers known as amino acids.
The Meaning of Polymers SPM polymerisation
’11/P1 amino acids ⎯⎯⎯⎯⎯⎯→ protein
(monomers) (polymer)
1 The word polymer originated from the Greek
polumeros which means ‘having many parts’. 4 Carbohydrates such as starch and cellulose
consist of monomers known as glucose
2 Polymers are large molecules made up of
many smaller and identical repeating units joined together chemically.
joined together by covalent bonds. These
polymerisation
small molecules that are joined into chains
are called monomers. glucose ⎯⎯⎯⎯⎯⎯→ carbohydrate
3 Polymerisation is the chemical process by
which the monomers are joined together to (monomers) (polymer)
9 form the big molecule known as the polymer. 5 Natural rubber found in latex consists of
monomers known as isoprene (2-methylbuta-
polymerisation
1,3-diene) joined together chemically.
A A A A A A ⎯→ –A–A–A–A–A–A– H CH3 H H H CH3 H H
⎮ ⎮ ⎮ ⎮ ⎮ ⎮ ⎮ ⎮
monomers polymer nC=C–C=C → —C–C=C–C —
⎮ ⎮ ⎮ ⎮
Or n A → (–A–)n where A = monomer H H H H n
n = a big number
4 A polymer is a macromolecule (a very big isoprene (monomer) natural rubber (polymer)
molecule). Hence, the relative molecular mass
of a polymer is large. Synthetic Polymers
5 The properties of a polymer are different from 1 Synthetic polymers are polymers made in the
its monomers. industry from chemical substances.
6 Polymers can be divided into 2 types:
2 Through scientific research, scientists are able
(a) Naturally occurring polymers
to copy the structures of natural polymers to
Polymers that exist in living things in
produce synthetic polymers.
nature (plants and animals)
(b) Synthetic polymer 3 Many of the raw materials for synthetic
Polymers that are man-made by chemical polymers are obtained from petroleum, after
processes in the laboratories. the refining and cracking processes.
Naturally Occurring Polymers 4 The types of synthetic polymers include
1 Naturally occurring polymers exist in plants (a) plastics
or animals.
(b) fibres
2 Examples of naturally occurring polymers are
(a) protein : in muscles, skin, silk, hair, wool (c) elastomers
and fur.
(b) carbohydrates : in starch and cellulose. 5 Plastics
(c) natural rubber : in latex.
(a) Thermoplastic is a polymer which, when
subjected to heat, becomes soft so they
can be moulded into various shapes.
(b) The properties of plastics are: light,
strong, inert to chemicals such as acids
and alkali and are insulators of electricity
and heat.
(c) Examples of plastics are polythene
(polyethylene), polyvinylchloride
(PVC), polypropene (polypropylene),
polystyr ene, Perspex and Bakelite.
6 Synthetic fibres
Carbohydrates such as starch and cellulose (a) Synthetic fibres are long chained polymers
are polymers
that withstand stretching.
Manufactured Substances in Industry 278
(b) Examples of synthetic fibres are nylon (b) Condensation polymerisation occurs when the
and Terylene. monomers with two functional groups combine to
form the polymer through a condensation reaction.
(c) Nylon is used to make ropes, fishing Examples of condensation polymers are nylon and
Terylene.
lines, stocking, clothing and parachutes. In general:
(d) Terylene is used to make clothing,
nA + nB → —( A – B —)n + nH2O
sleeping bags and fishing nets. Clothes monomer monomer condensation polymer
made from Terylene do not crease easily. AB
7 Elastomer
2 ’05
(a) An elastomer is a polymer that can regain
The diagram below shows a polymerisation process. 9
its original shape after being stretched or
H H H H
pressed.
(b) Both natural rubber and synthetic ⎮ ⎮
n C = C ⎯→~C — C~
rubber are examples of elastomers.
⎮ ⎮
(c) Examples of synthetic rubbers are neoprene H Cl H Cl n
and styrene-butadiene rubber (SBR).
Substance X Substance Y
(d) SBR is used to make car tyres.
8 There are two types of polymerisation processes: Which of the properties is identical for substance
(a) Addition polymerisation X and Y?
(b) Condensation polymerisation
9 Plastics such as polythene and PVC are A Density C Relative molecular mass
produced by addition polymerisation, whereas
synthetic fibres such as nylon and Terylene are
made by condensation polymerisation.
B Boiling point D Empirical formula
There are two types of polymerisation. Comments
(a) Addition polymerisation occurs when the monomers Substance X is a monomer while substance Y is a
polymer. A polymer has a higher density, melting
with double bonds combine to form the polymer point and boiling point than its monomer. The
through an addition reaction. Examples of addition relative molecular mass of a polymer is more than
polymers are polythene, polypropene, PVC, polystyrene that of a monomer but the percentage composition
and Perspex. and empirical formula are the same.
Examples:
Answer D
H H H H
⎮ ⎮ ⎮ ⎮
n C = C ⎯→ — C — C —
⎮ ⎮ ⎮ ⎮ 1 Nylon is a type of polyamide polymer, a polymer
H H H H n
with the amide (–CONH–) group.
ethene polythene n = a big number 2 Terylene is a type of polyester polymer, a polymer
H H H H with the ester (–COO–) group.
3 Neoprene is a type of synthetic rubber made from
⎮ ⎮ ⎮ ⎮
n C = C ⎯→ — C — C — the monomer, chloroprene.
4 Styrene-butadiene rubber (SBR) is a type of
⎮ ⎮ ⎮ ⎮
CH3 H CH3 H n synthetic rubber made from 2 types of monomers,
propene, C3H6 polypropene styrene and butadiene.
H H H H
⎮ ⎮ ⎮ ⎮
n C = C ⎯→ — C — C —
⎮ ⎮ ⎮ ⎮
Cl H Cl H n
chloroethene, polyvinylchloride The making of SBR is used in making
Terylene fibre tyres
C2H3Cl (PVC)
279 Manufactured Substances in Industry
Table 9.1 Some examples of synthetic polymers, their monomers and uses
Synthetic Polymer Monomer Uses
1 Polyethylene (PE) Ethene, C2H4 Plastic bags, shopping bags, plastic
IUPAC name: polythene containers, plastic toys, plastic cups and
plates
2 Polypropylene (PP) Propene, C3H6 Plastic bottles, bottle crates, plastic tables
IUPAC name: polypropene and chairs, car battery cases and ropes
3 Polyvinylchloride (PVC) Chloroethene, C2H3Cl Water pipe, shoes, bags, rain clothes,
IUPAC name: polychloroethene artificial leather and wire casing
9 4 Polystyrene (PS) Phenylethene, Packaging materials, heat insulators, toys,
IUPAC name: polyphenylethene C6H5CH = CH2 disposable cups and plates
Safety glass, airplane windows, car lamps,
5 Perspex (PP) Methyl-2-methyl traffic signs, lens, reflectors and toys
IUPAC name: poly(methyl-2- propenoate
methylpropenoate) (methylmetacrylate) Coatings for non-stick frying pans and
CH2 = C(CH3)CO2CH3 electrical insulators
6 Teflon (PTFE)
IUPAC name: polytetrafluoroethene Tetrafluoroethene, C2F4
7 Terylene Hexane-1, 6-diol Clothing, sleeping bags, sails, ropes and
and benzene-1, fishing net. Clothes made from Terylene
4-dicarboxylic acid do not crease easily
8 Nylon Hexane-1, 6-diamine Ropes, fishing lines, stocking, clothing,
and hexane-1, 6-dioic carpets and parachutes
acid
Issues of the Use of Synthetic Polymers in Every other micro-organisms. This will cause disposal
Day Life
problems as the polymers will not decay like
1 Synthetic polymers have been used widely
to replace natural materials such as metals, other organic garbage.
wood, cotton, animal skin and natural rubber 2 Discarded plastic items may cause blockage of
because of the following advantages:
(a) Strong and light drainage systems and rivers thus causing flash
(b) Cheap
(c) Able to resist corrosion floods.
(d) Inert to chemical reactions 3 Plastic bottles and containers that are not
(e) Easily moulded or shaped and be
coloured buried in the ground will become breeding
(f) Can be made to have special properties
according to specific needs grounds for mosquitoes which will cause
2 The use of synthetic polymers, however, results diseases such as dengue.
in environmental pollution problems. 4 Small plastic items that are thrown into the
Pollution Problem Caused by Synthetic rivers, lakes and seas are sometimes swallowed
Polymers by aquatic animals. These animals may die
from choking.
1 Most polymers are non-biodegradable, that 5 The open burning of polymers may release
is, they cannot be decomposed by bacteria or harmful and poisonous gases that will cause
air pollution. For example, the burning of
PVC will release hydrogen chloride gas which
contributes to the acid rain problem. The
burning of some polymers will release toxic
gas such as hydrogen cyanide.
6 The main source of raw materials for the
making of synthetic polymers is petroleum.
Petroleum is a non-renewable resource.
Manufactured Substances in Industry 280
Methods to overcome environmental 9.5 Glass and Ceramics
problems of polymers
1 The raw materials for making glass and
1 Reduce, reuse and recycle synthetic
polymers ceramics are obtained from the Earth’s crust.
(a) Reduce the use of non-biodegradable
polymers. 2 The main component of both glass and
(b) Polymers are collected and reused or
reprocessed to make new items. The 3 ceramics is silica or silicon dioxide, SiO2. in
biggest problem is the collection and Both glass and ceramics are used widely
separation. Not only must the plastics
be separated from other types of solid our daily life to replace metals because of the
waste but the different types of polymers
must be separated from each other. advantages above as well as their low cost of
2 Develop biodegradable polymers production.
These polymers can be decomposed by
bacteria, other microorganisms or simply 4 Both glass and ceramics have the same properties
by sunlight (photodegradable). One type
of biodegradable polymer was developed as follows:
by incorporating starch molecules into
the plastic materials so that they can (a) Hard but brittle 9
be decomposed by bacteria. However,
biodegradable polymers are usually more (b) Inert to chemical reactions
expensive.
(c) Insulators of electricity
(d) Poor conductors of heat and electricity
(e) Withstand compression but not tension
(stretching)
(f) Can be easily cleaned
5 The use of glass and ceramics also depends
on their differences. Table 9.2 shows the
differences between glass and ceramic.
Table 9.2 The differences in properties between glass
and ceramic
Glass Ceramic
9.4 Transparent Opaque
1 (a) What is a polymer? Softens when High melting point, hence retains
(b) Name two natural polymers that are used to
make clothing. heated shape on heating
(c) Name two synthetic polymers that are used
to make clothing. Impermeable Usually porous except when glazed
2 Fill in the blanks below.
Monomer Polymer
Ethene
In silicon dioxide, every silicon atom is bonded
Chloroethene covalently to 4 oxygen atoms in a tetrahedral shape.
Every oxygen atom is also bonded to two silicon atoms
to form a giant covalent molecule (Figure 9.15).
Polypropene
Polystyrene
3 State two properties of synthetic polymers that Figure 9.15 Structure of silicon(IV) oxide
will cause environmental pollution in the disposal
of synthetic polymers. State two methods to
overcome these problems.
281 Manufactured Substances in Industry
Table 9.3 The uses of glass
Property of glass Uses Examples
Inert Household materials Lamp, bottles, glasses, plates, bowls and
kitchen wares
Transparent Building materials Mirrors and window glass
Industrial materials Bulbs, glass tubes for radios, radars and
televisions
Inert and easily Scientific apparatus Lens, burettes, beakers, test tubes, Glass is transparent
cleaned conical flasks, glass tubes and prisms Ceramic is opaque and
has higher melting point
9 Table 9.4 Uses of ceramics SPM than glass
’05/P1
Property of ceramics Uses Examples
Hard and strong
Long lasting and non- Building materials Bricks, tiles and cement
corrosive
Electrical insulators Materials for decorative Plates, bowls, cooking utensils,
Inert and hard items porcelain and vases
Semiconductor type of To make electrical Insulators in toasters and irons,
ceramics insulating parts spark plugs in car engines
In surgical and dental Artificial hands, legs and teeth
apparatus
As microchips To make microchips in
computers, radios and televisions
Types, Properties, Composition and Uses the addition of chromium ions will give the glass
of Glass a green hue, cobalt ions will give a blue hue while
manganate ions will give a purple hue to the glass.
1 Fused glass is the simplest type of glass, which Composition of Ceramics
consists mainly of silica or silicon dioxide.
Occasionally a little boron oxide is added. 1 Ceramic is a manufactured substance made
from clay that is dried and then baked in a
2 Other types of glass are mainly metal silicates. kiln at high temperature.
3 Various types of glass can be produced by
2 The main constituent of clay is aluminate,
changing the composition of glass. Different types silica and feldspar.
of glass have different properties and they are
used for various specific purposes. The chemical 3 Kaolinite is an example of high quality white
composition, specific properties and uses of four clay that consists of hydrated aluminosilicate
types of glass are summarised in Table 9.5. crystals.
4 Coloured glass is produced by adding traces
of transition metal oxides to it. For example, 4 Red clay contains iron(III) oxide which gives
its red colour.
Table 9.5 Properties, composition and uses of different types of glass
Name of glass Properties Chemical composition Examples of uses
Fused glass • Very high softening point (1700 °C), SiO2 (99%) Telescope mirrors,
hence highly heat-resistant B2O3 (1%) lenses, optical fibres
and laboratory glass
• Transparent to ultraviolet and infrared light wares
• Difficult to be made into different shapes
• Does not crack when temperature changes
(very low thermal expansion coefficient)
• Very resistant to chemical reactions
Manufactured Substances in Industry 282
Name of glass Properties Chemical composition Examples of uses 9
Soda lime SiO2 (70%) Bottles, window-
glass • Low softening point (700 °C), hence does Na2O (15%) panes, light bulbs,
not withstand heating CaO (10%) mirr ors, flat glass,
Borosilicate Others (5%) glass-plates and
glass • Breaks easily bowls. (The most
• Cracks easily with sudden temperature SiO2 (80%) widely used type of
SPM B2O3 (15%) glass)
changes (high thermal coefficient of Na2O (3%)
’09/P1, expansion) Al2O3 (1%) Laboratory apparatus,
’10/P1 • Less resistant to chemical reactions cooking utensils,
• Easy to make into different shapes SiO2 (55%) electrical-tubes and
Lead glass PbO (30%) glass pipelines
• Quite high softening point (800 °C), K2O (10%)
hence it is heat-resistant Na2O (3%) Decorative items,
Al2O3 (2%) crystal glasswares,
• Does not crack easily with sudden lens, prisms and
change in temperature chandeliers
• Transparent to ultraviolet light
• More resistant to chemical reactions
• Does not break easily
• Low softening point (600 °C)
• High density
• High refractive index
• Reflects light rays and appears sparkling
The Uses of Improved Glass and Ceramics for Specific Purposes
Improved glass Examples of Improved Glass and Ceramics Improved Ceramics
Photochromic glass Superconductor
• Photochromic glass is a type of glass that is sensitive • Superconductors are a class of ceramics
to light intensity. The glass darkens when exposed that conducts electricity without
to sunlight but bec omes clear when light intensity resistance and without loss of electrical
decreases. energy.
• Photochromic glass is produced when a dispersion • Superconductor ceramics are used
of silver chloride, AgCl or silver bromide, AgBr is to make light magnets, electrical
added to normal glass. generators and electric motors.
Conducting glass Ceramic car engine block
• Conducting glass is a type of glass that can conduct • Clay heated with magnesium oxide
electricity. produces a type of ceramic that has a
high thermal resistance.
• Conducting glass is produced by embedding a thin
layer of conducting material in glass. • This type of ceramic is used for making
car engine blocks because it can resist
• A type of conducting glass is produced by adding a high temperatures.
layer of indium tin(IV) oxide (ITO) that acts as an
electrical conductor. This type of glass is used in the • At a higher temperature, the combustion
making of LCD (liquid crystal display) panel. of fuel becomes more efficient and
produces more energy with less
• Another type of conducting glass is made by pollution.
embedding thin gold threads in glass. Water
condenses as ice on the window panes of aircraft • Ceramic engines offer great advantages
at high altitudes and this obstructs the vision of in terms of fuel economy, efficiency,
the pilot. Hence, windows of aircraft are heated weight savings and performance.
by passing electric current through the gold threads
embedded in the glass.
283 Manufactured Substances in Industry
Main component is silica, SiO2
Glass Ceramic
9 Types of glass Examples of ceramics
• Fused glass (high heat resistance) • Tiles
• Soda lime glass (cannot withstand high temperatures) • Cement
• Borosilicate glass (can withstand high temperatures) • Bricks
• Lead glass (high refractive index) • Porcelain
Common properties • Resist compression Differences
• Hard but brittle • Can be easily cleaned • Glass is transparent, ceramic is opaque
• Inert to chemicals • Ceramic can withstand a higher temperature
• Heat and electrical resistance
than normal glass
9.5 3 In the making of composites, substances (known
as components) are combined to form new
1 Glass is a manufactured substance in industry. types of materials that can overcome the
(a) What is the major component of glass? limitations of the original materials.
(b) State a cheap source of this component.
(c) State four types of glass. 4 Most of the composite materials are comprised
of two phases: a continuous phase (also known
2 Glass and ceramics are both manufactured from as the base) and the dispersed phase (also
materials in the Earth's crust. known as the matrix).
(a) What is the common component found in
both glass and ceramics? 5 Composite materials are harder, stronger, lighter
(b) State the three similarities and three differences (lower density), more resistant to heat and
between glass and ceramics. corrosion and also made for specific purposes.
(c) State five uses of glass.
(d) State two examples of the use of ceramics in 6 A few types of composite materials and their
the building industry.
components are shown in Table 9.6.
3 State one main difference between soda lime
glass and borosilicate glass in terms of Table 9.6
(a) composition and (b) property.
Composite materials Components
9.6 Composite Materials
Reinforced concrete Concrete (cement, sand and
The Meaning of Composite Materials small pebbles) and steel
1 A composite material is a structural material Superconductor bYatrtriuiummcoaxribdoen(aYte2O(B3)a, CO3)
formed by combining two or more materials and copper(II) oxide (CuO)
with different physical properties, producing
a complex mixture. Fibre optic Glass {silica (SiO2), sodium
ccaarlcbiounmatoex(iNdae2(CCOaO3))a}nwd ith
2 The composite material produced will have different refractive indices
different properties far more superior to the
original materials. Fibreglass Glass fibre and polyester
(a type of plastic)
Photochromic glass Glass and silver chloride or
silver bromide
Manufactured Substances in Industry 284
1 Most types of material used in our daily life have (c) Glass and ceramics are brittle. resist high
certain limitations. For example: (d) Plastic and glass cannot
(a) Metals can be easily corroded and are
malleable and ductile. temperatures.
(b) Metals are good electrical conductors but the
existence of resistance results in the loss of a 2 With knowledge of the compositions, structures and
big amount of electrical energy as heat. properties of these materials, chemists are able to
develop new materials to suit specific purposes.
Comparison of the Properties of Composite Materials and Their Original Components
Reinforced concrete SPM 9
’07/P1, ’08/P1
1 Concrete is a composite material made from can support very heavy loads. It is used to
a mixture of sand and small stones bound construct framework for highways, brid
by cement. Concrete is strong in compression ges, oil platforms and high-rise buildings.
but brittle and weak in tension. Concrete
cannot withstand vibrations and will crack Figure 9.16 The formation of reinforced concrete
under the action of bending forces.
Dams are constructed by reinforced concrete which
2 Steel is strong in tension (high tensile is very strong
strength). But using thick steel columns
to support a heavy load is expensive.
Furthermore, steel corrodes easily.
3 Reinforced concrete is made by adding the
concrete mixture of cement, water, sand, chips
and small stones into a frame of steel bars or
steel wire netting (Figure 9.16). When set, a
composite material is formed.
4 Reinforced concrete is a stronger building
material as it combines the compressive
strength of concrete and tensile strength of
steel. In addition, it does not corrode easily.
Reinforced concrete is also relatively cheap
and can be moulded into any shape.
5 Steel and concrete have about the same coefficient
of expansion. Hence they are good composite
components and do not crack when mixed.
6 Reinforced concrete can withstand very
high applied forces (high pressure) and
Superconductors
1 In normal electrical conductors such as copper (known as the transition temperature). This
metal, the existence of resistance causes the
loss of electrical energy as heat. Furthermore, low temperature can only be achieved using
resistance increases as temperature increases.
liquid helium which is expensive.
2 Superconductors can conduct electricity with 4 When a mixture of copper(II) oxide (CuO),
zero resistance when they are cooled to extremely
low temperatures. Thus, superconductors barium oxide (BaO) and yttrium oxide
conduct electricity without any loss of energy. (Y2O3) is heated up, a type of ceramic with
the formula YBa2Cu3O7 is produced. This
3 Metals such as copper, can only achieve type of ceramic, known as perovskite or
superconductivity at a very low temperature YBCO, can attain superconductivity at 90 K
(–183°C). This temperature can easily be
attained by using the cheaper liquid nitrogen.
285 Manufactured Substances in Industry
5 The metal oxides (CuO, Y2O3 and BaO) are all amplifiers and computer parts. They are
electrical insulators. However when they are also used in magnetic resonance imaging
(MRI) – a type of medical imaging device.
combined to form a composite, the composite Superconductors are also used to make
stronger, lighter and more powerful
is a superconductor that can conduct very electromagnets. High – speed levitated trains
(trains that float on the railway track)
high current over long distance without any involve the use of electromagnets and
superconductors.
loss of energy.
6 Superconductors are used to make more
efficient generators, magnetic energy-storage
systems, transformers, electric cables,
Fibre optics (also known as optical fibres) SPM
’11/P1
9 1 Optical fibres are bundles of glass tubes with signals faster than metal
very small diameters. They are finer than
human hair and are very flexible. cables and occupies less
2 Fibre optics is a composite material that can space.
transmit electronic data or signals, voice and
images in a digital format, in the form of light 5 In the field of medicine,
along the fine glass tubes at great speeds.
a laser beam can be
3 Fibre optics consists of a core of glass of higher
refractive index enclosed by a glass cladding channelled through
of lower refractive index. A light wave entering
the fibre will travel along the glass tube due to fibre optics in operations
total internal reflection (Figure 9.17). to remove unwanted Fibre optics
4 In the field of telecommunications, fibre optics tissues. Fibre optics is
is used to replace copper wire in long distance also used in endoscopes: instruments that
telephone lines, mobile phones, video cameras are inserted into the body through the nose,
and to link computers within local area networks mouth or ear, for doctors to examine the
(LAN). Fibre optics uses light instead of electrons internal organs.
to carry data. Fibre optics carry more data (higher 6 Fibre optics is also used in instruments to
transmission capacity) with less interference, has inspect the interior of manufactured products.
a higher chemical stability and a lower material Figure 9.17 Cross section of a fibre optic
cost compared to metal communication cables
such as copper. Fibre optics can also send
Fibreglass
1 Plastic is light (with a low density), elastic, Boats built from fibreglass is light and strong.
flexible, but is brittle, not very strong and is
4 Fibreglass is an ideal material for making
inflammable (can catch fire). water storage tanks, boat hulls, swimming
2 Glass is hard and strong but is brittle, heavy pool linings, food containers, fishing rods,
car bodies, roofing, furniture and pipes.
(with a relatively high density) and has a low
compressive strength.
3 When glass fibre filaments are embedded in
polyester resin (a type of plastic), fibreglass
which is light, strong, tough, resilient,
inflammable, flexible with a high tensile
strength is produced. It can also be easily coloured,
moulded and shaped. A resilient material is one
that returns to its original shape after bending,
twisting, stretching and compression.
Manufactured Substances in Industry 286
Photochromic glass
1 Glass is transparent and is not sensitive to 7 Silver atoms and bromine gas recombine 9
according to the following reaction
light intensity.
2 Silver chloride or silver bromide is sensitive to Br2 + 2Cu+ → 2Br– + 2Cu2+ … (1)
Cu2+ + Ag → Cu+ + Ag+ … (2)
light. When exposed to light, these compounds
8 The overall reaction is
decompose to form dark silver particles.
3 In photochromic glass, silver chloride 2Ag + Br2 → 2AgBr
(AgCl) or silver bromide (AgBr) and a little 9 Photochromic glass is used to make camera
copper(I) chloride is embedded into the lens, car windshields, information display
structure of glass. panels, light intensity meters and optical
4 When exposed to ultraviolet light, the AgCl or switches.
AgBr decomposes to form silver and halogen
atoms. The fine silver which is deposited in
the glass is black and the glass is darkened.
For example:
uv light Photochromic glass is used to make lenses
2AgBr ⎯⎯⎯⎯→ 2Ag + Br2 that change from light to dark, eliminating
the neccessity for a separate pair of
5 Photochromic glass has the ability to change sunglasses.
colour and become darker when exposed to
ultraviolet light.
6 The photochromic glass will automatically
become clear again when the light intensity
is lowered, whereby silver is converted back
to silver halides.
Properties of composite materials compared to their components and the uses of composites
Composite Component Properties of Properties of composite Uses of composites
material component
Reinforced Concrete Hard but brittle, Stronger, higher tensile Construction of
concrete with low tensile strength, not so brittle, framework for
Steel strength does not corrode highways, bridges and
Super easily, can withstand high-rise buildings
conductor Copper(II) oxide, Hard with high higher applied forces
yttrium oxide and tensile strength and loads, relatively To make more
barium oxide but expensive and cheaper efficient generators,
can corrode transformers, electric
Conducts electricity cable, amplifiers,
Insulators of without resistance computer parts,
electricity when cooled by liquid stronger and lighter
nitrogen electromagnets
287 Manufactured Substances in Industry
Composite Component Properties of Properties of composite Uses of composites
material component
Fibre optics Glass of low Reflect light rays and Transmit data in
refractive index Transparent, does
Fibreglass Glass of higher not reflect light allow light rays to travel the form of light in
refractive index rays
Glass along the fibre telecommunications
Heavy, strong but
Polyester plastic brittle and non- Light, strong, Water and food storage
flexible tough, resilient and containers, boats,
flexible, with high swimming pool linings,
Light, flexible, tensile strength, not fishing rods, car bodies
elastic but weak inflammable and roofing
and inflammable
9
Transparent and
Photo Glass not sensitive to Sensitive to light: Photochromic optical
chromic light darkens when light lens, camera lens, car
glass Silver chloride or intensity is high, windshields, optical
silver bromide Sensitive to light becomes clear when switches, information
light intensity is low display panels and light
intensity meters
9.6 2 New materials are required to overcome new
challenges and problems we face in the
1 (a) State what is meant by the term composite changing world.
materials.
3 Synthetic materials are developed constantly
(b) Give five examples of composite materials due to the limitation and shortage of natural
and name one use for each example. materials.
2 (a) What is fibreglass? Explain how the properties 4 New needs and new problems will stimulate
of fibreglass are superior to that of its original the development of new synthetic materials.
components. For example, the use of new plastic compo
site material will replace metal in the making
(b) What is reinforced concrete? Give two of a stronger and lighter car body. This will
reasons why reinforced concrete is a strong save fuel and improve speed. Plastic compo
construction material. site materials may one day be used to make
organs for organ transplants in human bodies.
3 What is the advantage of using photochromic New superconductors made from composite
glass in the making of spectacles? Briefly explain materials are developed.
how this glass works.
5 The understanding of the interaction between
9.7 Appreciating Various different chemicals is important for both the
Synthetic Industrial development of new synthetic materials and
Materials the disposal of such synthetic materials as waste.
1 Continuous research and development 6 A responsible and systemic method of handling
(R & D) is required to produce better materials the waste of synthetic materials and their
used to improve our standard of living. by– products is important to prevent
environmental pollution. The recycling and
development of environmentally friendly
synthetic material should be enforced.
Manufactured Substances in Industry 288
1 Sulphuric acid is used to make other manufactured 9 The three aims of alloying are: 9
substances such as fertilisers, detergents, pesticides, (a) To increase the hardness and strength of a metal
polymers and paint pigments. (b) To prevent corrosion or rusting
(c) To improve the appearance of the metal surfaces
2 Sulphuric acid is manufactured by the Contact
process using vanadium(V) oxide as a catalyst. The 10 Polymers are large molecules made up of many
process involves three stages. smaller and identical repeating units (monomers)
joined together by covalent bonds.
Sulphur ⎯I → Sulphur dioxide ⎯II→ Sulphur trioxide
11 Some examples of synthetic polymers are polythene,
⎯II→I Sulphuric acid polypropene, P.V.C., polystyrene, perspex, Terylene
3 Sulphur dioxide gas can cause environmental and nylon.
pollution such as acid rain. 12 Synthetic polymers are strong and light, cheap, resist
4 Ammonia is used to make nitrogenous fertilisers corrosion and inert to chemical attacks. However,
they are nonbiodegradable and cause environmental
and nitric acid, and is used as a cooling agent in pollution problems.
refrigerators.
5 Ammonia is produced in the industry by the Haber 13 The main component of glass is silica or silicon
process with hydrogen gas and nitrogen gas and cdliaoyxid(ael,uSmiOin2o. sTihliceamte)a,insacnodns(tsitiulicean)tsaonfdcfeerldasmpiacrs. are
using iron powder as a catalyst.
6 An alloy is a mixture of two or more elements 14 Both glass and ceramics have the following properties:
with a certain fixed composition in which the major (a) Hard but brittle
component is a metal. (b) Inert toward chemicals
7 A pure metal is weak and soft because it contains (c) Insulators or bad conductors of heat and electricity
atoms of the same size in an orderly arrangement.
This enables the layers of atoms to slide over each 15 Some examples of glass are fused glass, soda lime
other easily. glass, borosilicate glass and lead glass.
8 In an alloy, foreign atoms of different sizes disrupt
the orderly arrangement of the metal atoms. This 16 A composite material is a structural material formed
prevents the layers of metal atoms from sliding over by combining two or more materials with different
each other easily. physical properties to produce a complex mixture.
17 Some examples of composites are reinforced
concrete, superconductors, fibre optic, fibreglass and
photochromic glass.
9
Multiple-choice Questions
9.1 Sulphuric Acid C Ammonia 3 Which of the following is true
D Ammonium sulphate about the manufacture of sulphuric
1 The uses of substance X is given acid by the Contact process?
below. 2 Which of the following is a use A Sulphur and vanadium(V)
of sulphuric acid? oxide are the raw materials.
• To make fertilisers A As an electrolyte in dry cells B Sulphur is converted into
• To manufacture detergents B As a raw material in making sulphur dioxide and then into
• To make paints explosives sulphur trioxide.
C As an electrolyte in the C Sulphur trioxide dissolves in
What of the following substances electroplating of metals water to form sulphuric acid.
could be X? D To clean the metal oxide D A pressure of 200
A Nitric acid layer of metals before atmosphere is used in the
B Sulphuric acid electroplating process.
289 Manufactured Substances in Industry
4 The manufacturing of sulphuric 9 Which of the following are true of D To lower the pressure
ammonia gas? required in the production of
acid in the Contact process ammonia
I It is a colourless and odourless
’06 involves several reactions. Which gas. 14 Which of the following are the
conditions in the production of
of the following is the reaction II It is lighter than air. ammonia by the Haber process?
III It is sparingly soluble in water.
that requires a temperature of IV It produces white fumes with I A temperature of about 450 °C
II A pressure of one atmosphere
450 – 550°C. hydrogen chloride gas. III Equal volumes of nitrogen gas
A I and IV only
A HS2SOS2+SO322OO++27H→+O2S2HOS2O4O2→→2SHO22S3H22OS7O4 B II and III only and hydrogen gas
C II and IV only IV The use of iron powder as a
B D III and IV only
C catalyst
D 10 Which of the following is a A I and II only
source of hydrogen for the Haber B I and IV only
9 5 In the Contact process, oleum is process? C II and III only
A The decomposition of water D I, II and IV only
produced when B Fractional distillation of liquid
A sulphur dioxide reacts with air 15 Ammonium nitrate is used
C Reaction of coke or natural as a fertiliser. What is the
oxygen. gas with steam
B sulphur dioxide dissolves in D Reaction of zinc metal with ’10 percentage by mass of nitrogen
sulphuric acid in ammonium nitrate? [Relative
water. atomic mass: H, 1; N, 14; O,
C sulphur trioxide dissolves in 11 Which of the following is the 16]
effect of using iron powder as A 17.5%
concentrated sulphuric acid. a catalyst in the production of B 17.7%
D sulphur trioxide dissolves in ammonia in the Haber process? C 28.6%
A The quantity of ammonia D 35.0%
water. produced is increased.
B The temperature required for 9.3 Alloys
6 Which of the following gas Haber process is reduced.
C The pressure required for 16 The alloying process increases
’08 dissolves in rainwater and Haber process is reduced. the hardness of a metal. This is
consequently kills trees and D The rate of reaction between because the foreign atoms added
hydrogen gas and nitrogen to a metal in the alloying process
corrodes concrete buildings? gas is increased. A increases the orderliness of
A Ammonia the arrangement of the metal
B Sulphur dioxide 12 Which of the following atoms.
C Carbon monoxide compounds reacts with ammonia B strengthens the bond between
D Carbon dioxide to produce urea, a type of the metal atoms.
fertiliser? C forms strong bonds between
7 Which of the following are caused A Carbon dioxide the metal atoms and the foreign
B Sulphuric acid atoms.
by the presence of sulphur C Phosphoric acid D makes it difficult for the layers
D Ethanoic acid of metal atoms to slide over
dioxide in the atmosphere? each other.
13 Which of the following is the
I Certain lung diseases and function of iron powder in the 17 Which of the following is not the
Haber process? aim of alloying iron to form steel?
bronchitis A To speed up the rate of A To make it harder
production of ammonia B To make it stronger
II An increase of acidity in B To increase the percentage C To make it more resistant to
yield of ammonia rusting
blood C To lower the cost of D To increase the melting point
production of ammonia
III An increase of acidity in rain
290
water
IV Corrodes concrete buildings
A I and II only
B III and IV only
C I, II and III only
D I, III and IV only
9.2 Ammonia and its Salts
8 Which of the following chemicals
is manufactured using ammonia
in the industry?
A Sodium hydroxide
B Hydrochloric acid
C Sulphuric acid
D Nitric acid
Manufactured Substances in Industry
18 Which alloy is correctly matched Polymer Monomer III Polymers promote excessive
to its uses? growth of algae in water.
I Natural rubber Isoprene
’11 II Carbohydrate Sucrose IV Polymers release toxic gases
III Polypropene Methylmethacrylate when burned.
Alloy Uses IV PVC Chloroethene
A I and IV only
A Duralumin Building of B II and III only
monuments C I, III and IV only
D II, III and IV only
B Brass Bodies of A II and III only
aeroplanes B I and IV only 9.5 Glass and Ceramics
C I, II and III only
C Bronze Frameworks of D I, II, and IV only 27 A transparent solid is formed
buildings when molten sand at high
temperature is cooled quickly.
D Stainless Making of 24 The diagram shows the repeating What is this solid? 9
steel surgical unit of a synthetic polymer. A Ceramic
instruments B Fused glass
H H C Soda lime glass
19 The alloy produced by the D Borosilicate glass
⎮ ⎮
addition of tin to copper metal is — C – C— 28 Which of the following are true
for both glass and ceramic?
known as ⎮ ⎮
A bronze CH3 CH3 I They contain a common
B brass component, silica.
C pewter Which of the following are true
D duralumin of this synthetic polymer? II They are electrical insulators.
I It is a type of addition polymer. III They are resistant to
20 Which of the following alloys is II It dissolves easily in hot water.
III It burns in air to produce chemicals.
suitable for the making of an IV They can resist compression.
carbon dioxide and water.
aircraft body? IV It has a high relative A I and II only
A Duralumin B III and IV only
B Bronze molecular mass. C I, II and III only
C Brass A I and II only D I, II, III and IV
D Cupro-nickel B III and IV only
C II and III only 29 Material Y has the following
D I, III and IV only properties:
21 Iron is alloyed to produce steel. 25 Which of the following are true ’09
Which of the following property about Terylene, a type of synthetic • Resistance towards
is not true of steel compared to chemical substances
polymer?
iron? • Low coefficient of thermal
A Harder I It is easily biodegradable. expansion
B More resistant to rusting
C More presentable II It burns easily. What is material Y ?
D A better electrical conductor A Bronze
III It is a type of fibre. B Polystyrene
9.4 Synthetic Polymers C Borosilicate glass
IV Its monomer is ethene. D Conducting glass
22 The polymer formed from the A I and IV only
polymerisation of phenylethene B II and III only 30 Which of the following glass has
is known as C II, III and IV only a low softening point and can
A polythene D I, II and III only be easily moulded into different
B polypropene shapes?
C polystyrene 26 Uncontrolled disposal of A Fused quartz glass
D polyvinyl chloride synthetic polymers will cause B Soda lime glass
environmental pollution. C Borosilicate glass
23 Which of the following are the Which of the following are D Photochromic glass
correct pairs of polymer and the characteristics of synthetic
monomer? polymers that causes this 31 Lead glass is very suitable for
environmental pollution? making fine glassware and art
objects because this type of glass
I Polymers are non-
biodegradable.
II Polymers increase the pH of
the water when dissolved in
water.
291 Manufactured Substances in Industry
9 A has a high refractive B Photochromic glass
index. C Lead glass
D Borosilicate glass Based on the diagram, why
B has a high softening is reinforced concrete often
point. 9.6 Composite Materials used more to build buildings
compared to concrete?
C is most transparent to ultra- 35 Which composite material A The steel bars cannot stretch
violet and infrared rays. is made of glass of different
and make it tough.
D is a good heat insulator. ’08 refractive index? B The concrete and the steel
A Fibreglass
32 What is the purpose of adding B Fibre optics bars can slide over each
feldspar to kaolin in the making C Photochromic glass
D Borosilicate glass other and make it flexible.
’05 of porcelain? C The steel bars fix the position
A To make kaolin softer 36 The supporting pillars of flyovers
B To make kaolin smoother of highways are made of of the concrete particles and
C To make kaolin harder
D To make porcelain that is ’06 substance X. make it hard.
inert towards chemicals Substance X has the following D The concrete particles are
properties : strong, not brittle,
33 The raw materials for making can withstand erosion and can evenly dispersed among the
soda lime glass are withstand weathering. Which of
the following is substance X? steel bars and make it able
I sodium carbonate A Concrete
II calcium carbonate B Steel to withstand vibrations.
III silicon dioxide C Marble
IV boron oxide D Reinforced concrete
A I and II only
B II and III only 37 The diagram shows the
C I, II and III only formation of a composite
D I, II, III and IV
’07 substance from its original
34 A decorative glassware components.
manufacturer wants to make a
display panel that is sensitive to
the intensity of light.
What is the most suitable
material?
A Conducting glass
Structured Questions
1 Diagram 1 shows a series of steps involved in the (c) (i) Name liquid Z. [1 mark]
production of sulphuric acid in industry starting from
sulphur. (ii) How is liquid Z formed from gas Y?
[1 mark]
Sulphur I Gas X II (d) Sulphuric acid is also formed when gas Y dissolves
Oxygen Oxygen
in water. Why is this not done in the manufacturing
of sulphuric acid in industry? [1 mark]
Sulphuric IV III (e) State two uses of sulphuric acid. [2 marks]
acid Liquid Z Gas Y
2 Diagram 2 shows how a type of fertiliser is produced.
Diagram 1 ’07 Process P Sulphuric acid Fertilliser
Process Q Ammonia X
(a) (i) Name gas X. [1 mark]
(ii) Write a balanced equation for the reaction
in step I. [1 mark]
(b) (i) Name gas Y. [1 mark] Diagram 2
(ii) State the conditions used in step II in order (a) Process P and process Q are industrial processes.
What are the names of each of these processes?
to produce a high percentage yield of gas Y. [2 marks]
[2 marks]
Manufactured Substances in Industry 292
(b) State the conditions for process Q. [3 marks] (ii) State a natural source of silica. [1 mark]
(c) (i) Name fertiliser X. (iii) W is a an important component of
(ii) Write a balanced equation for the formation borosilicate glass. What is W? [1 mark]
of fertiliser X. [2 marks] (b) (i) Name compound X. [1 mark]
(d) Calculate the mass of ammonia that is required (ii) Compound X can be used to make plastic
to react with 0.2 mol of sulphuric acid. chairs and tables. State one advantage of
[Relative atom mass: H, 1; N, 14] [2 marks]
this type of material as compared to metals.
(e) Name another type of fertiliser that is produced [1 mark]
when ammonia reacts with carbon dioxide. (c) (i) Identify component Y. [1 mark]
[1 mark]
(ii) Explain why magnalium is harder than pure
aluminium. [2 marks]
3 The flowchart in Diagram 3 shows the conversion of (d) Z can withstand high pressures and can support
nitrogen into various substances in steps I, II, III and IV.
very heavy loads. What is Z? [1 mark]
Nitrogen I Ammonia II Nitric acid (e) (i) Identify the type of compound T. [1 mark] 9
(ii) State a property of compound T. [1 mark]
+ Substance X III IV + Substance Y 5 Bronze, brass and duralumin are examples of alloys.
(a) What is meant by alloy? [1 mark]
Nitrate salt (b) Name the main element added to copper to form
(i) brass: [1 mark]
Diagram 3 (ii) bronze: [1 mark]
(a) Step I is an industrial process. State the conditions (c) What type of particles are present in pure
used for a good yield of ammonia in this process.
copper? [1 mark]
[3 marks]
(d) Draw a diagram to show the arrangement of
(b) Step II is also an industrial process. particles in
(i) Name this process. [1 mark] (i) pure copper
(ii) State the catalyst used in this process. (ii) bronze [2 marks]
[1 mark] (e) (i) Name the elements that are used to make
(c) State one physical property and one chemical the alloy duralumin. [1 mark]
property of ammonia. (ii) What is the advantage of duralumin compared
Physical property: to its main component? [1 mark]
Chemical property: [2 marks] (iii) State one use of the alloy duralumin.
(d) Name a possible compound for substance X in [1 mark]
step III and hence write a balanced equation that 6 Polyethene and polyvinyl chloride are examples of
synthetic polymers that are widely used in daily life.
occurs in step III. [2 marks]
(a) Name the process in which monomers are
(e) (i) Besides ammonia, name a compound that
joined together to form polymers. [1 mark]
may be substance Y in step IV. [1 mark]
(b) (i) Name the monomer that is used for the
(ii) Write a balanced equation for the reaction
making of polyethene. [1 mark]
in step IV. [1 mark]
(ii) Give a use of polyethene. [1 mark]
4 Table 1 shows the examples and components of five
different types of manufactured substances in industry. (c) The following diagram shows a part of the molecular
structure of polyvinyl chloride.
Type Example Components H Cl H Cl H Cl
⏐ ⏐ ⏐ ⏐ ⏐ ⏐
Glass Borosilicate Silica, sodium oxide and W ⎯C⎯ C⎯ C⎯ C⎯ C⎯ C⎯
glass ⏐ ⏐ ⏐ ⏐ ⏐ ⏐
H H H H H H
Polymer X Propene
Alloy Magnalium Aluminium and Y (i) Draw the structure of its monomer. [1 mark]
(ii) Polyvinyl chloride is widely used to make
Composite Z Concrete (cement, sand and
material small pebbles) and steel water pipes. State two advantages of PVC
pipes compared with iron pipes. [2 marks]
T Photochromic Glass and silver chloride (iii) State two ways in which polyvinyl chloride
glass can cause environmental pollution. [2 marks]
Table 1 (d) What is the source of the raw material used in
(a) (i) Give the chemical name for silica. [1 mark] producing polyethene and polyvinyl chloride?
[1 mark]
293 Manufactured Substances in Industry
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