Salts Notes

Chemistry Form 4 KSSM
AMARDEEP SINGH SIDHU 1

Chemistry Form 4 KSSM

Definition of Salt
Salt is an ionic compound formed when the hydrogen ion, H+ from the
acid is replaced with the metal ion or the ammonium ion, NH4+.
Physical Properties of Salt Crystals

Examples of Salts and Their Uses

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Chemistry Form 4 KSSM
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Chemistry Form 4 KSSM

Solubility of Salt in Water

Soluble salts are salts that dissolve in water at room temperature
and insoluble salts are salts that do not dissolve in water at room
temperature.

Types of salts Solubility

NO3- All are soluble
Cl-
All soluble except PAH – Persatuan Agama Hindu
SO42-
CO32- All soluble except PBC – Persatuan Bahasa Cina
NH4+, Na+ &
All insoluble except PAS
K+
All ammonium, sodium and potassium salts are
soluble

P  PbCl2 P  Potassium P  PbSO4
A  AgCl A  Ammonium B  BaSO4
H  Hg2Cl2 S  Sodium C  CaSO4

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Chemistry Form 4 KSSM

Preparation of Soluble Salts

Preparation of Soluble Ammonium, Sodium and Potassium Salts

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Chemistry Form 4 KSSM

Procedure:
1. Rinse a 25 cm3 pipette with a small amount of 2.0 mol dm-3

potassium hydroxide, KOH. Then, discard the solution.
2. Pipette accurately 25 cm3 of 2.0 mol dm-3 potassium hydroxide

solution, KOH and transfer into a conical flask.
3. Add a few drops of phenolphthalein indicator and swirl the flask.
4. Rinse a burette with 2.0 mol dm-3 hydrochloric acid, HCl. Then,

discard the solution.
5. Fill the burette with 2.0 mol dm-3 hydrochloric acid, HCl and

clamp the burette to the retort stand. Record the initial reading
of the burette.
6. Add acid into the conical flask slowly while swirling it.
7. Continue adding acid until the colour of the solution in the conical
flask changes from pink to colourless.
8. Record the final reading of the burette. Then, determine the
volume of 2.0 mol dm-3 hydrochloric acid, HCl required to
neutralise 25 cm3 of 2.0 mol dm-3 potassium hydroxide solution,
KOH (assuming the acid volume is V cm3).
9. Refill a new 25 cm3 of 2.0 mol dm-3 potassium hydroxide solution,
KOH into a conical flask without phenolphthalein indicator.
10. Add V cm3 of 2.0 mol dm-3 hydrochloric acid, HCl from a burette
into the conical flask and swirl the mixture to ensure the
mixture is even.
11. Pour the content of the conical flask into an evaporating dish.
12. Heat the solution slowly to evaporate the water so that a
saturated solution is obtained.
13. Let the saturated salt solution cool down to allow crystallisation
to occur.
14. Filter the contents of the evaporating dish to obtain potassium
chloride crystals, KCl.
15. Rinse the crystals with a little amount of distilled water.
16. Dry the salt crystals by pressing them between two pieces of
filter papers.

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Chemistry Form 4 KSSM

Preparation of Soluble Salts which are not Ammonium, Sodium and
Potassium Salts

Procedure:
1. Pour 20 cm3 of 2.0 mol dm-3 nitric acid, HNO3 into a beaker. Heat

the acid using medium heat.
2. Add copper(II) oxide powder, CuO gradually into the acid using a

spatula. Stir the mixture with a glass rod.
3. Continue adding copper(II) oxide, CuO until it is no longer

dissolved.
4. Filter the excess copper(II) oxide powder, CuO from the mixture.
5. Pour the filtrate into an evaporating dish and heat the filtrate till

a saturated salt solution is obtained.
6. Let the resulting saturated solution to cool until salt crystals are

formed.
7. Filter the content of the evaporating dish to obtain the salt

crystals. Rinse the crystals with a little amount of distilled water.
8. Dry the salt crystals by pressing them between two pieces of filter

papers.

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Chemistry Form 4 KSSM

Purification of Soluble Salts by Recrystallisation Method

Procedure:
1. Put the copper(II) sulphate crystals, CuSO4 into a beaker.
2. Add distilled water gradually while stirring. Heat the solution to

speed up the process of dissolving the salt.
3. Filter the hot salt solution to remove insoluble impurities.
4. Then, pour the filtrate into an evaporating dish and heat the

filtrate until a saturated solution is obtained.
5. Let the saturated solution cool until salt crystals are formed.
6. Filter the contents of the evaporating dish to get the salt crystals.

Rinse the crystals with a little amount of distilled water.
7. Dry the salt crystals by pressing them between two pieces of filter

papers.

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Chemistry Form 4 KSSM

Preparation of Insoluble Salts

Insoluble salts can be prepared through double decomposition
reaction. In this process, two salt solutions that contain insoluble salt
ions are needed.

Preparation of Insoluble Salts
1) To supply CATION, nitrate solution containing the CATION is

needed.
2) To supply ANION, PAS solution containing the ANION is needed.
3) Soluble Salt + Soluble Salt  Insoluble Salt
4) PA NO3- + PAS Cl-  PA Chloride

PBC NO3- + PAS SO42-  PBC Sulphate

Example:
a) Pb(NO3)2 + NaCl  PbCl2 + NaNO3

AgNO3 + NaCl  AgCl + NaNO3
b) Pb(NO3)2 + K2SO4  PbSO4 + KNO3

Ba(NO3)2 + K2SO4  BaSO4 + KNO3
Ca(NO3)2 + K2SO4  CaSO4 + KNO3

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Chemistry Form 4 KSSM

Preparing Insoluble Salts by Double Decomposition Reaction

Procedure:
1. 20 cm3 of 2.0 mol dm-3 barium chloride solution, BaCl2 is added into

20 cm3 of 2.0 mol dm-3 sodium sulphate solution, Na2SO4 in a
beaker.
2. The mixture is stirred thoroughly with a glass rod. A precipitate
of barium sulphate, BaSO4 is formed.
3. The mixture is filtered to obtain the white barium sulphate, BaSO4
as the residue.
4. The precipitate of barium sulphate, BaSO4 is rinsed with a little
amount of distilled water.
5. The salt crystals are dried by pressing them between two pieces
of filter papers.

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Chemistry Form 4 KSSM
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Chemistry Form 4 KSSM

Definition of Qualitative Analysis
Qualitative analysis of a salt is a technique used to identify the
cation and anion present in a salt by analyzing its physical and chemical
properties.

Anions and cations in salts can be identified through:

a) Colour of salt
b) Solubility of salt
c) Gas test
d) Effect of heat on salt
e) Confirmatory test for anions and cations

Colour of salt
1)

All Cu2+ salts are EXCEPT CuCO3
blue green

CuO
black

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Chemistry Form 4 KSSM

2) Fe2+  Green
ALL; Fe3+  Brown

3) Hot Cold
Brown Yellow
Salt Yellow White
Lead(II) oxide, PbO

Zinc oxide, ZnO

Solubility of Salt

Types of salts Solubility
All are soluble
NO3- All soluble except PAH – Persatuan Agama Hindu
Cl- All soluble except PBC – Persatuan Bahasa Cina
All insoluble except PAS
SO42-
CO32- All ammonium, sodium and potassium salts are
NH4+, Na+ & soluble

K+

P  PbCl2 P  Potassium P  PbSO4
A  AgCl A  Ammonium B  BaSO4
H  Hg2Cl2 S  Sodium C  CaSO4

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Chemistry Form 4 KSSM

Gas Test Colour of Smell of Effect on Confirmatory Test
Gas Gas Damp
Type of Gas and the Litmus When a glowing
procedure No Smell / wooden splinter is
Odourless No Effect lowered into the test
a) Oxygen Colourless tube of oxygen, the
1. Put two spatula of solid Colourless glowing wooden
potassium chlorate (V), Colourless splinter is lighted.
KClO3 into the test tube.
2. Heat the solid with high No Smell / No Effect When a lighted wooden
heat. Odourless splinter is placed near
3. Insert a glowing wooden
splinter into the test tube. the mouth of the test
tube of hydrogen, a
b) Hydrogen “pop” sound is
1. Put a few pieces of zinc produced.
powder, Zn into a test tube.
2. Add 4cm3 of dilute No Smell / Damp blue When carbon dioxide
sulphuric acid, H2SO4 into Odourless litmus turns gas is bubbled into
the test tube. to red limewater using a
3. Place a lighted wooden delivery tube, the
splinter near the mouth of limewater becomes
the test tube. milky/cloudy/chalky.

c) Carbon Dioxide
1. Put a spatula of solid zinc
carbonate, ZnCO3 into a test
tube.
2. Heat the solid with high
heat.
3. Flow the gas produced
into limewater.

d) Ammonia Colourless Pungent Damp red When a glass rod dipped
1. Put a spatula of solid Smell litmus turns into concentrated
ammonium chloride, NH4CL to blue hydrochloric acid is
into a test tube. placed near the mouth of
2. Add 4cm3 of dilute the test tube with
sodium hydroxide solution, ammonia, white fumes
NaOH into the test tube. are formed.
3. Heat the mixture slowly.
4. Then, place a piece of
moist red litmus paper to the
mouth of the test tube

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Chemistry Form 4 KSSM

e) Chlorine Yellowish Pungent Decolourise a) Bleaches a moist
1. Put a spatula of powdered s damp blue red litmus paper.
manganate (IV) oxide, Green/ Greenish Smell/ or red litmus
MnO2 into a test tube. b) Turns a moist blue
2. Carefully add 2cm3 of Yellow Choking litmus paper to red
concentrated hydrochloric and then bleaches it.
acid, HCl.
3. Heat the mixture slowly.
4. Then, place a piece of
moist blue litmus paper to
the mouth of the test tube.

f) Nitrogen Dioxide Brown Pungent Damp blue Turns moist blue litmus
1. Put a spatula of solid Smell litmus turns paper to red.
lead(II) nitrate, Pb(NO3)2 to red
into a test tube.
2. Heat the mixture with
high heat.
3. Then, place a piece of
moist blue litmus paper to
the mouth of the test tube.

g) Sulphur dioxide Colourless Pungent Damp blue When sulphur dioxide
1. Put a spatula of solid Smell litmus turns gas is bubbled into
sodium sulphite, Na2SO3 to red acidified potassium
into a test tube. manganate(VII)
2. Add 4cm3 of dilute solution, the purple
hydrochloric acid, HCl. colour is
3. Heat the mixture slowly. decolourised.(Or when
4. Flow the gas released into it is bubbled into
acidified potassium acidified potassium
manganate(VII) solution, dichromate(VI) the
KMnO4. colour changes from
orange to green.

h) Hydrogen chloride Colourless Pungent Damp blue When a glass rod dipped
1. Put a spatula of solid Smell litmus turns into concentrated
sodium chloride, NaCl into a to red ammonia is placed near
test tube. the mouth of the test
2. Add 2cm3 of concentrated tube with hydrogen
sulphuric acid, H2SO4 chloride, white fumes
carefully. are formed.
3. Heat the mixture slowly.
4. Dip a glass rod into
concentrated ammonia
solution, NH3.
5. Then, hold the dipped
glass rod to the mouth of the
test tube.

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Chemistry Form 4 KSSM Colourless No Smell / a) Changes the white
i) Water vapour Odourless colour of anhydrate
Copper(II) sulphate,
CuSO4 to blue

b) Turns anhydrate
cobalt(II) chloride
paper, CoCL2, from
blue to pink.

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Chemistry Form 4 KSSM

Effect of heat on salt
When salts are heated, there will be;

A colour change
Release of a certain gas
Release of water vapour

1. Heating Carbonate salt

 All carbonates are decomposed by heat to release CO2 except
K2CO3 and Na2CO3.

 MgCO3  MgO + CO2
 CO2 will turn limewater, Ca(OH)2 milky (CaCO3 + H2O)

2. Heating Nitrate salt

 Most metal nitrate decompose to produce a metal oxide,
nitrogen oxide and oxygen.

 KNO3 & NaNO3 produces oxygen gas and nitrites when heated.
 NO2 (brown gas: acidic), turn moist blue litmus paper into red.
 O2 relights glowing wooden splinter.

3. Heating Sulphate salt

 All sulphate salts are not decomposed by heat. heating
 Some (Fe, Zn, Cu) will decompose during strong

producing sulphur trioxide gas, SO3.
 Eg: ZnSO4  ZnO + SO3

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Chemistry Form 4 KSSM

4. Heating Chloride salt
 All chloride salts are not decomposed by heat except
ammonium chloride, NH4Cl
 NH4Cl produces white fumes
 Eg: NH4Cl  NH3 + HCl

Deduction Of Types Of Ion Present From Gas Produced

Gas produced Types of ion
CO2 CO32- (except Na2CO3 , K2CO3)
O2 NO3-
NO2 and O2 NO3- (except NaNO3 , KNO3)
SO2 SO42-
NH3 NH4+

Test for Anion

Anion Confirmatory Test
CO32- Bubbles with dilute acid and the gas produced will cause
limewater milky.
SO42- Mixed with dilute sulphuric acid and barium chloride and
a white precipitate is formed.
Cl- Mixed with dilute nitric acid followed by silver nitrate
solution and a white precipitate is formed.
NO3- Brown ring test and a brown ring will be formed.

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Chemistry Form 4 KSSM

Test for Cation

Cation NaOH Solution NH3 Solution
 No reaction
Ca2+  White precipitate formed
 White precipitate
 Not soluble in excess formed

Mg2+  White precipitate formed  Not soluble in excess
 White precipitate is
 Not soluble in excess
formed
Al3+  White precipitate formed  Not soluble in excess
 Soluble in excess  White precipitate

Zn2+  White precipitate formed formed
 Soluble in excess  Soluble in excess

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Chemistry Form 4 KSSM

Anion Test

1) HCl / HNO3 / H2SO4 CO2 Released C032-

2) HNO3 (dilute) & AgNO3 White Precipitate Cl-

3) HCl (dilute) & BaCl2 White Precipitate SO42-

4) H2SO4 (dilute) & FeSO4 & Brown Ring NO3-
H2SO4 (concentrated)

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Chemistry Form 4 KSSM

Flowchart

1) Test for Carbonate ion

 Add any dilute acid
Why we add dilute acid?

 All carbonates except K2CO3 and Na2CO3 release carbon dioxide
when heated.

 All carbonates produce carbon dioxide when reacts with dilute
acid.

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Chemistry Form 4 KSSM

2) Test for Chloride ion

 Silver ion is used to detect the presence of Chloride ion.
 An excess of nitric acid has to be added.
 If no effervescence occurs, the formation of White Precipitate

(AgCl) confirms the presence of Chloride ion.

Why nitric acid is added?
 Carbonate ion gives the same observation as chloride ion when
reacting with silver ion forming white precipitate (Silver
carbonate).
 If effervescence (presence of bubbles) occurs when nitric acid
is added, the presence of Carbonate ion is confirmed.

3) Test for Sulphate ion

 Barium ion is used to detect the presence of Sulphate ion.
 Hydrochloric acid is added in excess before adding barium

chloride solution.

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Chemistry Form 4 KSSM

Why hydrochloric acid is added?
 To eliminate the Carbonate ion that might be present (same
reason as in the test of Chloride ion).
 Carbonate ion gives the same observation when reacting with
barium ion forming white precipitate of Barium Carbonate
(insoluble salt).
 If effervescence occurs when hydrochloric acid is added, the
presence of Carbonate ion is confirmed.

4) Test for Nitrate ion

 Dilute sulphuric acid is added followed by Iron(II) Sulphate.
 Few drops of concentrated sulphuric acid is added to the

mixture.

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Chemistry Form 4 KSSM

Cation Test
Reaction between cations and sodium hydroxide, NaOH solution

 Ammonium ion will be formed
 Moist red litmus paper turns blue

Insoluble in excess amount of NaOH

Insoluble in  Soluble in excess amount of NaOH
excess  Produce colourless solution when

amount of excess NaOH is added
NaOH
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Chemistry Form 4 KSSM

Reaction between cations and ammonia, NH3 solution

Insoluble in excess amount of NH3
 Soluble in excess amount of NH3
 Produce dark blue solution

Insoluble in excess amount of NH3

 Soluble in excess

amount of NH3
 Produce colourless

solution

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Chemistry Form 4 KSSM

Observation NaOH solution NH3 solution
Green precipitate Fe2+ Fe2+
Brown precipitate Fe3+ Fe3+
Blue precipitate Cu2+ Cu2+
White precipitate
The white precipitate is soluble in MCZAP MZAP
excess
The white precipitate is insoluble ZAP Cu Z
in excess
NOTE: MC MAP

 M = Mg2+
 C = Ca2+
 Z = Zn2+
 A = Al3+
 P = Pb2+
 Cu = Cu2+

Cation Other Reagents

NH4+ Nessler’s reagent: Brown precipitate
Ca2+ Concentrated H2SO4: White precipitate
Pb2+ KI: Yellow precipitate

Fe2+ K3Fe(CN)6: Dark blue precipitate
Fe3+ K4Fe(CN)6: Dark blue precipitate

KSCN: Blood-red solution

Test for Cations

Al3+ and Pb2+ give the same observation with aqueous sodium

hydroxide, NaOH and aqueous ammonia, NH3.

How to distinguish them?
 Add aqueous potassium iodide (KI)
 If Pb2+ is present, a bright yellow precipitate of lead(II) iodide,
PbI2 will be formed
 Al3+ will not give precipitate with potassium iodide, KI.

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