A 3.93×10^–5 M solution of methylamine, a weak organic base, has a pH of 9.56. What are the K_b and pK_b for this base?

• A. K_b = 1.3×10^–9, pK_b = 8.88
• B. K_b = 2.8×10^–10, pK_b = 9.56
• C. K_b = 1.9×10^–15, pK_b = 14.71
• D. K_b = 4.4×10^–4, pK_b = 3.36

Answer: (D)