Question

1. Objective type questions

A. Fill in the blank spaces:

(i) When copper sulphide is treated with hydrochloric acid, it gives a ______ smelling gas hydrogen sulphide. [fine/foul]

Answer 1

• A chemical reaction may take place when two or more reactants come in contact with one another resulting in the formation of new substances called products accompanied by the transfer of energy among them.
• When sodium sulfide reacts with hydrochloric acid, it gives off a gas hydrogen sulfide, having the smell of rotten eggs.
• $\underset{\mathrm{Sodium}\mathrm{Sulfide}}{{\mathrm{Na}}_2\mathrm{S}\left(\mathrm{g}\right)}+\underset{\mathrm{Hydrochloric}\mathrm{acid}}{2\mathrm{HCl}\left(\mathrm{g}\right)}\to \underset{\mathrm{Sodium}\mathrm{Chloride}}{2\mathrm{NaCl}\left(\mathrm{aq}\right)}+\underset{\mathrm{Hydrogen}\mathrm{Sulphide}}{{\mathrm{H}}_2\mathrm{S}\left(\mathrm{g}\right)}$

Therefore, when copper sulfide is treated with hydrochloric acid, it gives a foul-smelling gas hydrogen sulfide.