mohd faisol mansor/chemistry form 4/chapter 8

CHAPTER 8
SALTS
A salt is an ionic
substance produced
when the hydrogen
ion of the acid is
replaced by metal
ion or an ammonium
ion.

The salt consists of two

parts, cation from base
and anion from acid.

NaCl
NaOH
(Base)

HCl
(Acid)

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Table of Salts
Complete the table below.

Metal ion

Sulphate salt
(SO42-)

Chloride salt
(Cl-)

Nitrate salt
(NO3-)

Carbonate salt
(CO32-)

K+

K2SO4

KCl

KNO3

K2CO3

Na+
Ca2+
Mg2+
Al3+
Zn2+
Fe2+
Sn2+
Pb2+
Cu2+
Ag+
NH4+
Ba2+
Based on the table above, mark the insoluble salt.

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SOLUBLE & INSOLUBLE SALTS

SALT

SOLUBLE

INSOLUBLE

K+ , Na+ , NH4+

All soluble

none

Nitrate salts
(NO3- )

All nitrate salts

none

Chloride salts
(Cl-)

Sulphate salts
(SO42-)

Carbonate
salts
(CO32-)

Oxide salts
(O2-)

All chloride salts

Lead (II) chloride,

PbCl2
Silver chloride, AgCl
Mercury chloride,
HgCl

All sulphate salts

Lead (II) sulphate

Calcium sulphate
Barium sulphate

Sodium carbonate,
Na2CO3
Potassium carbonate,
K2CO3
Ammonium carbonate,
(NH4)2CO3
Sodium oxide, Na2O
Potassium oxide, K2O
Calcium oxide, CaO

All others carbonate

salts

All oxide salts

(slightly soluble)

Hydroxide salts
(OH-)

Sodium hydroxide, NaOH

Potassium hydroxide, KOH
Calcium hydroxide,
Ca(OH)2

All hydroxide salts

(slightly soluble)

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Preparation and Purification of Soluble Salts

Soluble salt can be prepared by the following ways:
1. Reaction between acid and alkali - preparation for
sodium, potassium and ammonium salts only.
Eg: HCl(aq) + NaOH(aq)
NaCl(aq) + H2O(l)
[write the step of preparation of the salts on the diagram]

Buret
HCl solution

NaOH solution

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Preparation and Purification of Soluble Salts

Soluble salt can be prepared by the following ways:
1. Reaction between acid and metal oxide
Eg: HNO3(aq) + MgO(s)
Mg(NO3)2 (aq) + H2O(l)
2. Reaction between acid and metal
Eg: H2SO4(aq) + Zn (s)
ZnSO4(aq) + H2 (g)
3. Reaction between acid and metal carbonate
Eg: HCl(aq) + CaCO3(s)
CaCl2(aq) + CO2(g) + H2O(l)
[write the step of preparation of the salts on the diagram]

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mohd faisol mansor/chemistry form 4/chapter 8

Crystallization
is a process to crystallize
the soluble salts.
Recrystallization
process will carried out in
order to get pure and
more defined crystal

Physical characteristic of
crystals
Fixed geometrical shapes
such as a cuboids,
rhombic or prism
Flat surface, straight edges
and sharp angles.

Same shapes for same

substance but differ in
sizes
Fixes angle between two
neighbouring surfaces.

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Preparation of insoluble salts

An insoluble salt is prepared through precipitation method.
Aqueous solution of two soluble salts are mixed to form
insoluble and soluble salt:
[write the general equation of preparation insoluble salt]

The reaction is called double decomposition.

Two solutions contain ions that make up the insoluble salts.
Eg: Preparation of lead(II) iodide salt by using lead(II)
nitrate solution and potassium iodide solution.
[write the balance chemical equation]

Double Decomposition

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Chemical and Ionic Equation

Chemical and ionic equation can be written for all reaction
That used to prepare salts.
Example: Formation of precipitate Barium Sulphate, BaSO4.
1. Chemical Equation:
BaCl2 (aq) + Na2SO4 (aq)

BaSO4(s) + 2NaCl (aq)

2. Ionic Equation:

Ionic equation shows the ions take part in the reaction.

Exercise
1. Change each of the following word equations to a balanced
chemical equation.
a) Sulphuric acid + zinc

zinc sulphate + hydrogen gas.

b) Silver nitrate + potassium iodide

c) Nitric acid + chromium(III) hydroxide

silver iodide + potassium

nitrate

chromium(III) nitrate
+ water

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mohd faisol mansor/chemistry form 4/chapter 8

2. Complete the following equations.

a) HCl (aq) +

NiO (s)

b) HNO3 (aq) + Ca(OH)2 (aq)

c) H2SO4 (aq) + MgCO3 (s)
3. Write an ionic equation for each reaction between the following
pairs of substances.
a) Sulphuric acid, H2SO4 and barium hydroxide, Ba(OH)2 solution

b) Ammonium chloride, NH4Cl solution and silver nitrate, AgNO3

solution.

c) Lead(II) nitrate, Pb(NO3)2 solution and copper(II) sulphate,

CuSO4 solution.

d) Iron(III) oxide, Fe2O3 and hydrochloric acid, HCl.

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mohd faisol mansor/chemistry form 4/chapter 8

Constructing Ionic Equation using the Continuous Variation Method

Continuous variation method can be used to construct ionic

equation for the formation of insoluble salts.
Fixed volume of a reactant A is react with varying volumes
of a reactant B to determine the mole ratio of reactant A
that react completely with reactant B.
If x mol of reactant A with y mole of reactant B, than the
empirical formula for insoluble salt is A x B y.
Example:
2Fe3+ (aq) + 3CO32- (aq)

Fe2(CO3)3 (s)

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mohd faisol mansor/chemistry form 4/chapter 8

Example
1.

6.0 cm3 of 0.2 mol dm-3 Xn+ solution reacts completely with 4.0
cm3 of 0.1 mol dm-3 Ym- solution to form a salt XmYn. Write the
ionic equation and hence determine the empirical formula of
the salt reaction.

2.

18.0 cm3 of 0.1 mol dm-3 solution of Px+ ions reacts completely
with 9.0 cm3 of 0.1 mol dm-3 solution of Qy- ions to form a salt
PxQy. Write the ionic equation and hence determine the
empirical formula of the salt in this reaction.

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mohd faisol mansor/chemistry form 4/chapter 8

Solving Problem Involving Calculation of Quantities of Reactants or

Product in Stoichiometric Reactions
Since the quantities of chemicals involved in a reaction are in term
of moles, the quantities of chemicals (volume, mass and number of
particles) must be converted to moles in calculation regarding
quantities of reactant and products.

Exercise
1. Calculate the number of moles of aluminium sulphate
produced by the reaction of 0.2 mole of sulphuric acid with
excess aluminium oxide.
[0.067 mole]

2. 2.0 g of sodium hydroxide reacts with excess sulphuric acid.

What is the mass of sodium sulphate produces
[RAM: H,1 ; O,16 ; Na,23 ; S,32]
[ 3.55 g]

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3. What the volume of carbon dioxide gas evolved at s.t.p when

2.1 g of magnesium carbonate reacts with excess nitric acid.
[ RAM: C,12;O,16;Mg,24; s.t.p = 22.4 dm3]
[ 560 cm3]

4. What is the mass of magnesium required to react with 20 cm3 of

2.0 mol dm3 hydrochloric acid to produce 120 cm3 of hydrogen
at temperature? [RAM: Mg,24 ; 1 mol = 24 dm3 at room temp.]
[ 0.12 g]

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Qualitative Analysis of Salts

Colour & Solubility of the Salt

GREEN

PALE GREEN

Iron(II) Sulphate, FeSO4

Iron(II) Nitrate, Fe(NO3)2
Iron(II) Chloride, FeCl2

REDDISH-BROWN

Iron(III) Sulphate, Fe2(SO4)3

Iron(III) Nitrate, Fe(NO3)3
Iron(III) Chloride, FeCl3

GREEN

INSOLUBLE

Copper(II) Carbonate, CuCO3

BLUE

Copper(II) Sulphate, CuSO4

Copper(II) Nitrate, Cu(NO3)2
Copper(II) Chloride, CuCl2

YELLOW/BROWN
[depend on concentration]

INSOLUBLE

Iron(III) Oxide, Fe2O3

BLUE

BROWN

BLACK

INSOLUBLE

Copper(II) Oxide, CuO

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Colour & Solubility of the Salt

WHITE

COLOURLESS

Potassium Oxide, K2O

Sodium Oxide, Na2O
Calcium Oxide, CaO

WHITE [cold]

WHITE

Magnesium Oxide, MgO

Aluminium Oxide, Al2O3

YELLOW [cold]

INSOLUBLE

YELLOW [hot]

INSOLUBLE

Zinc Oxide, ZnO

INSOLUBLE

BROWN [hot]

Lead(II) Oxide, PbO

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Gas test
Oxygen gas

hydrogen gas
Wooden splinter

Hydrogen gas, H2

Oxygen gas, O2

Carbon dioxide gas

sulphur dioxide gas

Carbon dioxide

HCl acid

Sulphur dioxide

HCl acid
Sodium Sulphite, Na2SO3

Sodium Carbonate,
Na2CO3

chlorine gas
ammonia gas
Red litmus paper

Glass rod dipped into

concentrated HCl acid
White fumes

Chlorine gas, Cl2

Ammonia gas, NH3

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mohd faisol mansor/chemistry form 4/chapter 8

EFFECT OF HEAT ON SALTS

Carbonate salts
Sodium carbonate & potassium carbonate are very stable. They do
not decompose on heating.
Carbonate Salt

Heating

Metal Oxide +

Carbon dioxide

Heating

Carbonate salts
[ white ]

residue
[ white ]

Salts
1.

Calcium carbonate

2.

Magnesium carbonate

3.

Aluminium carbonate

Chemical Equation

Heating

Carbonate salts
[ white ]

Salts
1.

residue
[ yellow hot ]
[ white cold ]

Chemical Equation

Zinc carbonate

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mohd faisol mansor/chemistry form 4/chapter 8

Carbonate Salt

Heating

Metal Oxide +

Carbon dioxide

Heating

Carbonate salts
[ brown ]

residue
[ brown ]

Salts
1.

Chemical Equation

Iron(III) carbonate

Heating

Carbonate salts
[ green ]

residue
[ black ]

Salts
1.

Chemical Equation

Copper(II) carbonate

Heating
Carbonate salts
[ white ]

Salts
1.

residue
[ brown hot ]
[ yellow cold ]

Chemical Equation

Lead(II) carbonate
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mohd faisol mansor/chemistry form 4/chapter 8

Carbonate Salt

Heating

Metal + Carbon dioxide + Oxygen gas

Heating

Carbonate salts
[ white ]

residue
[ grey ]

Salts
1.

Chemical Equation

Mercury(II) carbonate

Heating

Carbonate salts
[ white ]

residue
[ shiny grey ]

Salts
1.

Chemical Equation

Silver carbonate

Heating
Carbonate salts
[ white ]

Salts
1.

residue
[ golden yellow ]

Chemical Equation

Aurum(II) carbonate
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mohd faisol mansor/chemistry form 4/chapter 8

nitrate salts

Nitrate Salt

Heating

Metal Oxide + Oxygen gas + Nitrogen dioxide

Heating

nitrate salts
[ white ]

residue
[ white ]

Salts
1.

Calcium nitrate

2.

Magnesium nitrate

3.

Aluminium nitrate

Chemical Equation

Heating

nitrate salts
[ white ]

Salts
1.

residue
[ yellow hot ]
[ white cold ]

Chemical Equation

Zinc nitrate

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mohd faisol mansor/chemistry form 4/chapter 8

Nitrate Salt

Heating

Metal Oxide + Oxygen gas + Nitrogen dioxide

Heating

nitrate salts
[ brown ]

residue
[ brown ]

Salts
1.

Chemical Equation

Iron(III) nitrate

Heating

nitrate salts
[ blue ]

residue
[ black ]

Salts
1.

Chemical Equation

Copper(II) nitrate

Heating
nitrate salts
[ white ]

Salts
1.

residue
[ brown hot ]
[ yellow cold ]

Chemical Equation

Lead(II) nitrate
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mohd faisol mansor/chemistry form 4/chapter 8

Nitrate Salt

Heating

Metal + Nitrogen dioxide + Oxygen gas

Heating

nitrate salts
[ white ]

residue
[ grey ]

Salts
1.

Chemical Equation

Mercury(II) nitrate

Heating

nitrate salts
[ white ]

residue
[ shiny grey ]

Salts
1.

Chemical Equation

Silver nitrate

Nitrate Salt

Heating

Metal nitrite + Oxygen gas

Heating

nitrate salts
[ white ]

Salts
1.

Potassium nitrate

2.

Sodium nitrate

residue
[ white ]

Chemical Equation

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mohd faisol mansor/chemistry form 4/chapter 8

TEST FOR ANIONS

Unknown aqueous salt solution

Salt needed to be
dissolved into water
first to produce
aqueous salt
solution.

[ state the procedure ]

[ state the procedure ]

[ state the procedure ]

OBSERVATION

[ state the procedure ]

[ label the diagram ]

OBSERVATION

OBSERVATION

[ label the diagram ]

[ label the diagram ]

[ label the diagram ]

CONCLUSION

CONCLUSION

CONCLUSION

CONCLUSION

[ state the anion ]

[ state the anion ]

[ state the anion ]

OBSERVATION

[ state the anion ]

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mohd faisol mansor/chemistry form 4/chapter 8

TEST FOR CATIONS

Unknown aqueous salt solution

Salt needed to be
dissolved into water
(soluble salts) or in
dilute acid then
filtered (insoluble
salts) first to produce
aqueous salt solution.

Add NaOH drop by drop

No precipitate

White precipitate

Coloured precipitate
Green

Add NaOH drop by drop until excess

Dissolve in excess NaOH

Brown

Insoluble in excess NaOH

Blue

* All coloured ions insoluble in excess NaOH

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mohd faisol mansor/chemistry form 4/chapter 8

TEST FOR CATIONS

Unknown aqueous salt solution

Salt needed to be
dissolved into water
(soluble salts) or in
dilute acid then
filtered (insoluble
salts) first to produce
aqueous salt solution.

Add NH3 drop by drop

No precipitate

White precipitate

Coloured precipitate
Green

Add NH3 drop by drop until excess

Dissolve in excess NH3

Brown

Insoluble in excess NH3

Blue

Dissolved in excess NH3

Dark blue solution

* Fe2+ & Fe3+ ions insoluble in excess NH3

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mohd faisol mansor/chemistry form 4/chapter 8

Confirmatory Test for Cation

Cation

Procedure

Observation

Fe 2+
Fe 3+
Pb 2+
NH4 +

Exercise
1.

Identify the aqueous solutions based on the test and observation given.
Type
a.
b.
c.
d.
e.

f.

Observation

Potassium thiocyanate,
KSCN, solution is added.
Potassium iodide, KI, solution
is added.
Ammonia solution, NH3, is
added until excess.
A little hydrochloric acid is
added.
A sulphuric acid, iron(II)
sulphate solution and
concentrated sulphuric acid
is added.
Ammonia solution is added
until excess.

K2 CO3

ZnCl2

PbCl2

Answer

Blood red solution formed.

Yellow precipitate is
formed.
Blue precipitate dissolve to
form dark blue solution.
Effervescene occur and
lime water turn into chalky.
Brown ring formed.
White precipitate
dissolved.

CuSO4

NaNO3

FeCl3

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