Assuming Equal Concentrations of Conjugate Acid and Base, Which One

Multiple Choice

Assuming equal concentrations of conjugate acid and base, which one of the following mixtures is suitable for making a buffer solution with an optimum pH of 4.6-4.8?

A) CH₃COONa/CH₃COOH (K_a = 1.8 × 10^-5)
B) NH₃/NH₄Cl (K_a = 5.6 × 10^-10)
C) NaOCl/HOCl (K_a = 3.2 × 10^-8)
D) NaNO₂/HNO₂ (K_a = 4.5 × 10^-4)
E) NaCl/HCl