Classify HClO as a Strong Base, Weak Base, Strong Acid, or Weak Acid and Determine the pH of a 0.07 M HClO Aqueous Solution

HClO, or hypochlorous acid, is classified as a weak acid. This is because, in solution, it does not fully dissociate into its ions. Instead, it establishes an equilibrium where only a fraction of the HClO molecules release protons (H⁺).

To find the pH of a 0.07 M HClO solution, we first need to know the dissociation constant (K_a) for HClO, which is approximately 3.0 x 10^-8. We set up the equilibrium expression for the dissociation of HClO:

HClO ⇌ H⁺ + ClO^–

Applying the expression for K_a:

K_a = [H⁺][ClO^–] / [HClO]

Assuming that the initial concentration of HClO is 0.07 M and that ‘x’ is the change in concentration (the amount that dissociates), we can write:

K_a = (x)(x) / (0.07 – x) ≈ (x²) / 0.07, since x is small compared to 0.07.

Substituting the K_a value:

3.0 x 10^-8 = x² / 0.07

Solving for x:

x² = 3.0 x 10^-8 * 0.07 = 2.1 x 10^-9

x ≈ 4.58 x 10^-5 M (this is the concentration of H⁺ ions).

Next, we can find the pH:

pH = -log[H⁺] = -log(4.58 x 10^-5) ≈ 4.34.

Therefore, rounding off, the pH of the 0.07 M HClO solution is approximately 4.3.

So the correct answer is c) 4.3.