The acid-dissociation constant, Ka, for benzoic acid is 6.5 × 10-5.Calculate the base-dissociation constant, Kb, for the conjugate base of benzoic acid.

For a conjugate acid–base pair at 25°C, Ka × Kb = Kw = 1.0 × 10⁻¹⁴. Thus, Kb = (1.0 × 10⁻¹⁴) ÷ (6.5 × 10⁻⁵) ≈ 1.5 × 10⁻¹⁰. The base-dissociation constant is therefore 1.5 × 10⁻¹⁰, choice D.

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