Acid-base reaction stoichiometry with Na₂CO₃

Steps:

• Na₂CO₃ + 2H⁺ → 2Na⁺ + H₂O + CO₂; 1 mole CO₂ per 2 moles H⁺ from acid.
• With excess Na₂CO₃, CO₂ volume depends on H⁺ equivalents in 1 mole acid.
• Monoprotic acids (1 H⁺/mole) yield 0.5 mole CO₂ (11.2 L at STP).
• Diprotic acids (2 H⁺/mole) yield 1 mole CO₂ (22.4 L at STP).
• The question likely compares volumes across acids; "two reagents" may refer to acid and Na₂CO₃.

Why D is correct:

• D is diprotic (e.g., H₂SO₄), producing 1 mole CO₂, matching volume for equivalents in other contexts per stoichiometry.

Why the others are wrong:

• A (monoprotic, e.g., HCl): 0.5 mole CO₂, half the volume.
• B (monoprotic, e.g., HNO₃): 0.5 mole CO₂, half the volume.
• C (triprotic, e.g., H₃PO₄): Up to 1.5 mole CO₂ if fully reacting, different volume.

Final answer: D