A 0.10 M HClO(aq) solution is prepared. Calculate the pH of this solution given that the Ka of HClO is 1.58 x 10^-4.

• A. pH = 2.00
• B. pH = 4.00
• C. pH = 5.00
• D. pH = 4.83

Answer: (D)

Verified step by step guidance

1. Identify the chemical equilibrium involved: HClO(aq) ⇌ H⁺(aq) + ClO⁻(aq). The dissociation of hypochlorous acid (HClO) in water is a weak acid equilibrium.
2. Write the expression for the acid dissociation constant (Ka): Ka = [H⁺][ClO⁻] / [HClO]. Given that Ka = 1.58 x 10^-4, this expression will help us find the concentration of H⁺ ions.
3. Assume that the initial concentration of HClO is 0.10 M and that the change in concentration due to dissociation is x. Therefore, at equilibrium, [H⁺] = x, [ClO⁻] = x, and [HClO] = 0.10 - x.
4. Substitute these equilibrium concentrations into the Ka expression: 1.58 x 10^-4 = (x)(x) / (0.10 - x). Since HClO is a weak acid, we can assume x is small compared to 0.10, simplifying the expression to 1.58 x 10^-4 ≈ x² / 0.10.
5. Solve for x, which represents [H⁺], and then calculate the pH using the formula pH = -log[H⁺]. This will give you the pH of the solution.