Which of the Following Acids (Listed with K_a Values) and Their

Multiple Choice

Which of the following acids (listed with K_a values) and their conjugate base would be the best choice to make a buffer with a pH of 10.40?

A) C₆H₅COOH, K_a = 6.5 × 10^-5
B) HF, K_a = 3.5 × 10^-4
C) HClO, K_a = 2.9 × 10^-8
D) HCN, K_a = 4.9 × 10^-10
E) HClO₂, K_a = 1.1 × 10^-2