Chlorous acid (HClO2) is used in bleaching textiles, leather, paper, and fibers. The value of Ka for chlorous acid is 1.2 ✕ 10−2. Calculate the pH of a 0.12 M solution of chlorous acid.

1.36

Explanation:

HClO2  ⇄  H+  +  ClO2-

           [HClO2]          [H+}         [ClO2-]

initial:  0.12       0         0

change: -x        +x       +x

equil:   0.12-x    x          x

[H+][ClO2-] / [HClO2] = Ka = 1.2 * 10^-2

x* x / 0.12 - x = 1.2 * 10^-2

x^2 = (2.4  *  10^-3) - (1.2 * 10^-2)x

x^2 +  (1.2 * 10^-2)x – (2.4 * 10^-3) = 0

Upon solving for x,

x = 0.04335

[H+] = 0.04335

pH = -log[H+]

pH = -log(0.04335)  = - (-1.36) = 1.36

the answer is symmetrical : )