Question

Determine the [H3O+] in a 0.265 M HClO solution. The Ka of HClO is 2.9 × 10-8.

a. 1.3 × 10-6 M
b. 7.7 × 10-9 M
c. 1.1 × 10-10 M
d. 8.8 × 10-5 M
e. 4.9 × 10-4 M

Answer 1

8.8X10^-5 M

Step-by-step explanation:

HClO is a weak acid that ionizes by the equation:

HClO + H2O <--> H3O+ + ClO-

Ka = [H3O+][ClO-]/[HClO] = 2.9X10^-8

Let [H3O+] = [ClO-] = x. [HClO] = 0.265 -x.

Because Ka is small, assume x << 0.265 and can be ignored. Then,

Ka = 2.9X10^-8 = x^2 / 0.265

x = [H3O+] = 8.8X10^-5 M