(a) "No precipitation reaction can occur without exchange of ions between the two reactants." Justify this statement giving a balanced chemical equation for the reaction.

OR

(b) Giving one example of each, differentiate between a displacement reaction and a double displacement reaction.

(a) The statement is true because in a precipitation reaction, the reactants exchange partners, resulting in the formation of a precipitate. For example, when sodium sulphate reacts with barium chloride, the sulphate ions from the sodium sulphate combine with the barium ions from the barium chloride to form a precipitate of barium sulphate.

Na2SO4(aq) + BaCl2(aq) $\rightarrow$ BaSO4(s) + 2NaCl(aq)

OR

(b) Displacement reaction: A reaction in which one element displaces another element from a compound is called a displacement reaction. For example, when zinc reacts with copper sulphate, zinc displaces copper from copper sulphate, resulting in the formation of zinc sulphate and copper.

Zn(s) + CuSO4(aq) $\rightarrow$ ZnSO4(aq) + Cu(s)

Double displacement reaction: A reaction in which two compounds react to form two new compounds by exchanging partners is called a double displacement reaction. For example, when sodium sulphate reacts with barium chloride, the sulphate ions from the sodium sulphate combine with the barium ions from the barium chloride to form a precipitate of barium sulphate, while the sodium ions from the sodium sulphate combine with the chloride ions from the barium chloride to form sodium chloride.

Na2SO4(aq) + BaCl2(aq) $\rightarrow$ BaSO4(s) + 2NaCl(aq)