Hypochlorous acid (HClO) has an acid ionization constant, K _a, equal to 2.9×10^{- 8}. What is the pH of a 0.20 M aqueous solution of hypochlorous acid?

Question

Quizplus · Accepted Answer

The equation for the acid ionization of hypochlorous acid is:
HClO(aq) ⇌ H⁺(aq) + ClO⁻(aq)
The acid ionization constant expression is:
K= [H⁺][ClO⁻]/[HClO]
We know that K = 2.9×10⁻⁸.
Let x be the concentration of H⁺ and ClO⁻ ions formed during the ionization process. Since the initial concentration of HClO is 0.20 M, the equilibrium concentration of HClO is (0.20 - x).
Using the acid ionization constant expression, we can set up the following equation:
2.9×10⁻⁸ = x² / (0.20 - x)
Solving for x, we get x = 5.3×10⁻⁵.
The pH of the solution is:
pH = -log[H⁺] = -log(x) = 4.12.

Hypochlorous Acid (HClO) Has an Acid Ionization Constant, K a

Hypochlorous Acid (HClO) Has an Acid Ionization Constant, K _a