Question

8. What is the concentration of ClO– in a 0.010 M solution of HClO at 25°C? The value of Ka at this temperature is 3.0 × 10−8.

Answer 1

                                                                  HClO + H₂O H₃O⁺ + ClO^-

Initial concentration (M):                            0.010                  0            0

Change in concentration (M):                     -X                      X            X

Equilibrium concentration (M):                (0.010 - X)            X             X

K_a of HClO = 3.0 × 10⁻⁸

Now,

K_a = [H₃O⁺][ClO^-]/[HClO]

or, 3.0 × 10⁻⁸ = (X)(X)/(0.010 - X)

or, 3.0 × 10⁻⁸ = X²/0.010

or, X² = 0.0000000003

or, X = 1.73 x 10^-5

or, [ClO^-] = 1.73 x 10^-5 M

Therefore, the concentration of ClO^- in a 0.010 M solution of HClO = 1.73 x 10^-5 M