There are two major classes of double displacement reactions.
They are,
(i) Precipitation Reactions:
When aqueous solutions of two compounds are mixed, if they react to form an insoluble compound and a soluble compound, then it is called precipitation reaction.
Pb(NO3)2(aq) + 2KI(aq)→ PbI2(*)↓ + 2KNO3(aq)
(ii) Neutralisation Reactions:
Another type of displacement reaction in which the acid reacts with the base to form a salt and water. It is called ‘neutralisation reaction’ as both acid and base neutralize each other.
NaOH(aq) + HCl(aq) ⟶ NaCl(aq) + H2O(I)
