Carbonate ions act as a Brønsted-Lowry base in ammonium carbonate decomposition

Steps:

• Ammonium carbonate formula is (NH₄)₂CO₃, containing NH₄⁺ and CO₃²⁻ ions.
• On warming, it decomposes: (NH₄)₂CO₃ → 2NH₃ + CO₂ + H₂O, producing ammonia.
• NH₄⁺ donates H⁺ (acts as acid), while CO₃²⁻ accepts H⁺ to form HCO₃⁻ intermediate.
• This proton acceptance defines CO₃²⁻ as a Brønsted-Lowry base.

Why B is correct:

• CO₃²⁻ accepts a proton from NH₄⁺, matching the Brønsted-Lowry base definition as a proton acceptor.

Why the others are wrong:

• A: CO₃²⁻ accepts protons, so it cannot act as a Brønsted-Lowry acid (proton donor).
• C: No electron transfer occurs; this is an acid-base reaction, not oxidation.
• D: No gain of electrons; reduction is absent in this decomposition.

Final answer: B