Calculate the pH of the solution

Question

A solution is prepared at 25 °C that is initially 0.42M in chlorous acid (HCIO₂), a weak acid with K_a = 1.1 × 10^-2, and 0.26M in potassium chlorite (KCI0₂)

Calculate the pH of the solution

Round your answer to 2 decimal places.

Answer 1

The solution of HClO₂ and KClO₂ is a buffer solution since it contains a weak acid, and the salt of that acid.

We can use the Henderson Hasselbalch equation to find the pH of such a solution:

pH = pKa + log [salt] / [acid]

pKa = -log Ka = -log 1.1x10^-2 = 1.96

pH = 1.96 + log [0.26 M) / (0.42 M) = 1.96 + log 0.619

pH = 1.96 - 0.21

pH = 1.75