QuestionIonic equilibrium / pH
Which one of the following statements regarding acid-base property is NOT correct?
- (a) pH + pOH = 14, for all aqueous solutions
- (b) The pH of 10⁻⁸ (M) HCl solution is 8
- (c) The conjugate base of H₂PO₄⁻ is HPO₄²⁻
- (d) H₂SO₄ is a strong acid in aqueous solution
Answer: (b) The pH of 10⁻⁸ (M) HCl solution is 8
(b) ✘ 10⁻⁸ M HCl cannot be basic: water's own H⁺ (10⁻⁷) dominates; [H⁺] ≈ 1.05 × 10⁻⁷ → pH ≈ 6.98. (c) ✔ H₂PO₄⁻ − H⁺ → HPO₄²⁻. (d) ✔. (a) holds at 25 °C. NOT correct → (b).