This document describes the purification of soluble salts through recrystallization and the preparation of insoluble salts through precipitation reactions. It discusses physical characteristics of salt crystals such as their geometric shape and fixed angles. It then provides examples of precipitation reactions used to prepare specific insoluble salts like lead (II) sulfate, copper (II) carbonate, and barium sulfate through a double decomposition reaction between aqueous solutions of their ions. General and ionic chemical equations are given to represent these precipitation reactions.

1. NURUL ASHIKIN BT. ABD RAHMAN PART 2

2. Learning Outcome
 Describe the purification of soluble salts by
recrystallisation.
 List physical characteristics of crystals.
 Describe the preparation of insoluble salts.
 Write chemical and ionic equations for
reactions used in the preparation of salts.

3. Impure Salt Dissolved in distilled water
Dilute solution + Heat and evoporate to get
impurities saturated solution + impurities
Saturated Cool it. Pure crystals
solution + Crystallisation formed. Filter
impurities process begins crystal out.

4. CuSO4
NaCl
KMnO4
FeSO4
K2Cr2O7

5. Fixed geometrical shapes
Flat surface, straight edges
and sharp angles.
Fixed angles between two
adjacent surfaces.
Same substance have same
shapes but different sizes

6. • Use precipitation methode by double
decomposition reaction.
• Aqueous solutions containing the ions of the
soluble salt are mixed together to form the
salt.
• The precipitated salt is the filtered
out, washed and dried.

7. Lead (II) Sulphate is prepared as follows:
Lead (II) Sulphate
Cation: Choose Anions: choose
any soluble lead any soluble
Pb2+ SO4 2- sulphate salt
(II) salt
Ex:Pb(NO3)2 Ex: K2SO4
Chemical equation
Pb(NO3)2 (aq) + K2SO4 (aq)  PbSO4 (s) + 2KNO3 (aq)
Chemical equation
Pb2+ (aq) + SO4 2- (aq)  PbSO4 (s)

8. The general equation can be represented by:
AY (aq) + BX (aq)  AX (s) + BY (aq)
Ionic equation can be represented by
nAm+ (aq) + mX n- (aq)  AnXm (s)

9. Copper (II) Carbonate is prepared as follows:
Copper (II)
Carbonate
Cation: Choose Anions: choose
any soluble any soluble
Cu2+ CO3 2-
Copper (II) salt Carbonate salt
Ex: CuSO4 Ex: Na2CO3
Chemical equation
CuSO4 (aq) + Na2CO3 (aq)  CuCO3 (s) + Na2SO4 (aq)
Chemical equation
Cu2+ (aq) + CO3 2- (aq)  CuCO3 (s)

10. Barium Sulphate is prepared as follows:
BariumSulphate
Cation: Choose Anions: choose
any soluble any soluble
Ba2+ SO4 2-
Barium salt sulphate salt
Ex: BaCl2 Ex: Na2SO4
Chemical equation
BaCl2 (aq) + Na2SO4 (aq)  BaSO4 (s) + 2NaCl (aq)
Chemical equation
Ba2+ (aq) + SO4 2- (aq)  BaSO4 (s)