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Which of the following pairs would form a buffer solution? (A) HCl(aq) / Cl⁻(aq) (B) H₂PO₄⁻(aq) / PO₄³⁻(aq) (C) H₂SO₄(aq) / HSO₄⁻(aq) (D) CH₃COOH(aq) / CH₃COO⁻(aq) - HSC - SSCE Chemistry - Question 9 - 2005 - Paper 1
Question 9
Which of the following pairs would form a buffer solution? (A) HCl(aq) / Cl⁻(aq) (B) H₂PO₄⁻(aq) / PO₄³⁻(aq) (C) H₂SO₄(aq) / HSO₄⁻(aq) (D) CH₃COOH(aq) / CH₃COO⁻(aq)
Worked Solution & Example Answer:Which of the following pairs would form a buffer solution? (A) HCl(aq) / Cl⁻(aq) (B) H₂PO₄⁻(aq) / PO₄³⁻(aq) (C) H₂SO₄(aq) / HSO₄⁻(aq) (D) CH₃COOH(aq) / CH₃COO⁻(aq) - HSC - SSCE Chemistry - Question 9 - 2005 - Paper 1
Step 1
Identify which pairs can form a buffer solution
Answer
A buffer solution consists of a weak acid and its conjugate base or a weak base and its conjugate acid.
- Option A: HCl is a strong acid and Cl⁻ is its conjugate base, making this pair incapable of forming a buffer since no weak acid is present.
- Option B: H₂PO₄⁻ is a weak acid and PO₄³⁻ is its conjugate base, which can form a buffer solution.
- Option C: H₂SO₄ is a strong acid while HSO₄⁻ is its conjugate base, therefore not capable of forming a buffer as it does not include a weak acid with a conjugate base.
- Option D: CH₃COOH is a weak acid and CH₃COO⁻ is its conjugate base, making this pair a buffer solution as well.
Step 2