X is a strong monoprotic acid that fully ionizes and liberates CO2 from carbonates

Steps:

• Compound X yields two ions per mole in solution, indicating a strong 1:1 electrolyte like H+ and anion.
• Reaction with ammonium carbonate ((NH4)2CO3) produces an acid gas (CO2), characteristic of acids displacing CO2 from carbonates.
• Bases like hydroxides react with (NH4)2CO3 to evolve ammonia (basic gas), not CO2.
• Among options, only nitric acid fits as a strong acid fully dissociating into two ions and producing CO2.

Why C is correct:

• Nitric acid (HNO3) fully ionizes as H+ + NO3- (two ions) and reacts: 2HNO3 + (NH4)2CO3 → 2NH4NO3 + CO2 + H2O.

Why the others are wrong:

• A. Calcium hydroxide (Ca(OH)2) ionizes into three ions (Ca2+ + 2OH-) and produces NH3 gas.
• B. Ethanoic acid (weak) partially ionizes, not yielding two full moles of ions.
• D. Sodium hydroxide (NaOH) ionizes into two ions but produces NH3 (basic gas) with (NH4)2CO3.

Final answer: C