What is the [H₃O⁺] in a buffer that consists of 0.30 M HCOOH and 0.20 M HCOONa? [K_a(HCOOH) = 1.7 × 10^-4] A) 1.1 × 10^-4^M B) 2.6 × 10^-4^M C) 4.3 × 10^-4^M D) 6.7 × 10^-5^M E) 1.7 × 10^-4^M

Question

Quizplus · Accepted Answer

The pH of a buffer solution can be calculated using the Henderson-Hasselbalch equation: pH = pKa + log([A-]/[HA]), where [A-] is the concentration of the conjugate base and [HA] is the concentration of the acid. For this buffer, pKa = -log(1.7 × 10^-4) = 3.77, [A-] = 0.20 M (HCOONa), and [HA] = 0.30 M (HCOOH). Plugging these values into the equation gives pH = 3.77 + log(0.20/0.30) = 3.77 - 0.176 = 3.594. Since pH = -log[H+], [H+] = 10^-pH = 10^-3.594 = 2.57 × 10^-4 M, which is closest to choice B, 2.6 × 10^-4 M.

What Is the [H3O+] in a Buffer That Consists of 0.30

What Is the [H₃O⁺] in a Buffer That Consists of 0.30