Question

A solution reacts with zinc granules to give a gas which burns with a ‘pop’ sound. The solution contains ______.

Options

• Mg(OH)₂

• Na₂CО₃

• NaCl

• HCl

Answer 1

A solution reacts with zinc granules to give a gas which burns with a ‘pop’ sound. The solution contains HCl.

Explanation:

When highly reactive zinc granules come into contact with an acid such as hydrochloric acid, a single-displacement reaction occurs. The zinc metal displaces hydrogen from the acid, forming zinc chloride and releasing flammable hydrogen gas. This released hydrogen gas is highly combustible and rapidly combusts with a signature explosive pop sound when exposed to a flame. The other options listed are a weak base (Mg(OH)₂) and neutral salts (Na₂CO₃, NaCl), none of which will generate this outcome with zinc.

\[\ce{Zn_{(s)} + 2HCl_{(aq)} -> ZnCl2_{(aq)} + H2_{(g)}}\]