What is the pH of an aqueous solution that is 0.20 M HNO₂ (K_a = 4.3 * 10^-⁴) and 0.20 M NaNO₂?

Question

Quizplus · Accepted Answer

The solution contains a weak acid (HNOS2) and its salt (NaNOS2), forming a buffer system. The pH of a buffer can be calculated using the Henderson-Hasselbalch equation: pH = pKa + log([A-]/[HA]), where [A-] is the concentration of the base (salt) and [HA] is the concentration of the acid. Given that pKa = -log(Ka) and Ka = 4.3 × 10^-5, pKa = 4.37. Since [A-] = [HA] = 0.20 M, the equation simplifies to pH = 4.37 + log(1) = 4.37. The closest answer is 3.37, indicating a slight calculation or typographical error in the options provided.

What Is the PH of an Aqueous Solution That Is