Question

Dilute hydrochloric acid is added to granulated zinc taken in a test tube. The following observations are recorded. Point out the correct observation.

• A. The surface of metal becomes shining.
• B. The reaction mixture turns milky.
• C. Odour of a pungent-smelling gas is recorded.
• D. A colourless and odourless gas is evolved.

Answer 1

The correct option is D

A colourless and odourless gas is evolved.

The explanation for the correct option:

(D) When diluting hydrochloric acid is added to granulated zinc placed in a test tube, zinc metal is converted to zinc chloride and hydrogen gas is evolved in the reaction.
The reaction of zinc with hydrochloric acid is as follows: $\underset{\mathrm{Zinc}}{\mathrm{Zn}\left(\mathrm{s}\right)}+\underset{\mathrm{Hydrochloric}\mathrm{acid}}{2\mathrm{HCl}\left(\mathrm{l}\right)}\to \underset{\mathrm{Zinc}\mathrm{chloride}}{{\mathrm{ZnCl}}_2\left(\mathrm{l}\right)}+\underset{\mathrm{Hydrogen}\mathrm{gas}}{{\mathrm{H}}_2\left(\mathrm{g}\right)}$

In the reaction, we can see that a zinc chloride salt is formed and hydrogen gas is evolved. The evolved hydrogen gas is colorless and odorless. From the solution of zinc chloride, hydrogen gas evolves as bubbles.

Therefore option (D) i.e. colorless and odorless gas is evolved is the correct answer.