Question

When hydrogen sulphide gas is passed through a blue solution of copper sulphate, a black precipitate of copper sulphate is obtained and the sulphuric acid so formed remains in the solution. The reaction is an example of :-
A) A combination reaction B) A displacement reaction
C) A decomposition reaction D) A double decomposition reaction

Answer 1

The reaction is an example of :-

(D) A double decomposition reaction

- The balanced chemical equation of the given reaction is as follows:

CuSO4 (aq) + H2S (g) → CuS (s) + H2SO4 (aq)

- The blue CuSO4 solution reacts with H2S gas to produce black ppt of CuS along with H2SO4.

- Here, sulphur replaces sulphate from CuSO4 and sulphate replaces sulphur from H2S and takes each other's place.

- Hence, it is a double displacement reaction.