Question

Iqbal treated a lustrous, divalent element M with sodium hydroxide. He observed the formation of bubbles in a reaction mixture. He made the same observations when this element was treated with hydrochloric acid. Suggest how can he identify the produced gas. Write chemical equations for both the reactions.

Answer 1

In the question the element M is described as shiny, lustrous, and divalent so, it must be a metal with +2 oxidation state.

• A base interacts with a metal in the first sentence, and an acid reacts with a metal in the second. As a result, hydrogen gas is the most likely product of these reactions.
• Reaction with base:

$\mathrm{M}+2\mathrm{NaOH}\to {\mathrm{Na}}_2{\mathrm{MO}}_2+{\mathrm{H}}_2$

• Reaction with acid

$\mathrm{M}+2\mathrm{HCl}\to {\mathrm{MCl}}_2+{\mathrm{H}}_2$

• On reacting with acid the given metal evolution of hydrogen gas is observed.

Identification of gas

• To identify the produced gas, lighted matchstick should be brought near the gas. If match stick burns with a “pop” sound, it indicates the evolution of Hydrogen gas.

Thus, when Iqbal treats a lustrous, divalent element M with sodium hydroxide and hydrochloric acid, Hydrogen gas is evolved.