(a)

Define a double displacement reaction.

(b)

Write the chemical equation of a double displacement reaction which is also a (i) Neutralization reaction and (ii) Precipitation reaction. Give justification for your answer.

(a) Reactions in which there is an exchange of ions between the reactants. (b) (i) \[\bullet \mathrm{HCl}+\mathrm{NaOH} \longrightarrow \mathrm{NaCl}+\mathrm{H}_{2} \mathrm{O} \quad \text { (or any other reaction) } \] -Acid reacts with base forming salt and water.

(ii) \[\text { - } \mathrm{Na}_{2} \mathrm{SO}_{4}+\mathrm{BaCl}_{2} \longrightarrow \mathrm{BaSO}_{4}+2 \mathrm{NaCl} \quad \text { (or any other reaction) } \] -Insoluble substance or precipitate \(\displaystyle \left(\mathrm{BaSO}_{4}\right)\) is formed.