Determine the pK_a given the K_b of the following bases:
i) NH₃ K_b = 1.76 × 10⁻⁵ ; NH₄⁺ pK_a = ____________
ii) C₆H₅NH₂ K_b = 3.9 × 10⁻¹⁰ ; C₆H₅NH₃⁺ pK_a = ____________

• A. i. pK_a = 18.754, ii. pK_a = 23.41
• B. i. pK_a = 9.246, ii. pK_a = 4.59
• C. i. pK_a = 4.754, ii. pK_a = 9.41
• D. i. pK_a = −9.246, ii. pK_a = −4.59

Answer: (B)