Question

When dilute hydrochloric acid is added to zinc pieces taken in a test tube:

• A. No changes take place
• B. The color of the solution becomes yellow
• C. A pungent-smelling gas gets liberated
• D. Small bubbles of hydrogen gas appear on the surface of pieces of zinc

Answer 1

The correct option is D

Small bubbles of hydrogen gas appear on the surface of pieces of zinc

The explanation for the correct option:

(D) Small bubbles of hydrogen gas appear on the surface of pieces of zinc

When zinc$\left(\mathrm{Zn}\right)$ pieces are added to dilute hydrochloric acid$\left(\mathrm{HCl}\right)$, zinc chloride$\left({\mathrm{ZnCl}}_2\right)$ and hydrogen gas$\left({\mathrm{H}}_2\right)$ are produced.

$\mathrm{Zn}\left(\mathrm{s}\right)+2\mathrm{HCl}\left(\mathrm{aq}\right)\to {\mathrm{ZnCl}}_2\left(\mathrm{aq}\right)+{\mathrm{H}}_2\left(\mathrm{g}\right)$

The explanation for the incorrect options:

(A) No changes take place.

The reaction between dilute $\mathrm{HCl}$ and zinc takes place, so changes do take place.

(B) The color of the solution becomes yellow.

Aqueous zinc chloride is transparent in color.

(C) A pungent-smelling gas gets liberated.

Hydrogen gas is an odorless gas.

Therefore, the correct option is (D).