Which of the following is NOT a Brønsted–Lowry acid?

• A. H₂CO₃
• B. HCO₃^–
• C. CO₃^2–
• D. H₂O
• E. H₃O⁺

Answer: (C)

Verified step by step guidance

1. Understand the concept of a Brønsted–Lowry acid: A Brønsted–Lowry acid is a substance that can donate a proton (H⁺) to another substance.
2. Examine each option to determine if it can donate a proton: Start with H₂CO₃, which is carbonic acid and can donate a proton to form HCO₃⁻.
3. Consider HCO₃⁻: This is the bicarbonate ion, which can donate a proton to form CO₃²⁻, thus acting as a Brønsted–Lowry acid.
4. Evaluate CO₃²⁻: The carbonate ion cannot donate a proton because it does not have any hydrogen atoms to donate, making it not a Brønsted–Lowry acid.
5. Review H₂O and H₃O⁺: Water (H₂O) can donate a proton to form OH⁻, and H₃O⁺ (hydronium ion) is a well-known Brønsted–Lowry acid as it can donate a proton to form H₂O.