The K_aof hypochlorous acid (HClO) is 3.00 × 10^-⁸at 25.0 °C. Calculate the pH of a 0.0385 M hypochlorous acid solution.

Question

Quizplus · Accepted Answer

The equation for the dissociation of hypochlorous acid is:

HClO (aq) ⇌ H+ (aq) + ClO– (aq)

The acid dissociation constant, Ka, is given by:

Ka = [H+][ClO–]/[HClO]

At equilibrium, the concentrations of H+ and ClO– will be equal, so we can write:

Ka = [H+]2/[HClO]

Rearranging this equation, we get:

[H+] = sqrt(Ka*[HClO])

The value of Ka for HClO is given by the expression:

Ka = [H+][ClO−]/[HClO] = 3.00 × 10−8

[HClO] is given as 0.0385 M. Substituting these values into the equation for [H+], we get:

[H+] = sqrt(3.00 × 10−8 * 0.0385) = 1.43 × 10−4

The pH is defined as the negative logarithm (base 10) of the [H+]:

pH = -log[H+] = -log(1.43 × 10−4) = 4.47

Therefore, the best choice is E, with a pH value of 4.47.

The Ka of Hypochlorous Acid (HClO) Is 3