What is the pH of a 0.016 M HClO₄(aq)at 25 $\circ$ C? (K_w = 1.01 $\times$10^-14)

Question

Quizplus · Accepted Answer

HClO is a weak acid, and its ionization reaction is as follows:
HClO ⇌ H+ + ClO-
The equilibrium constant expression for the above reaction is:
Ka = ([H+][ClO-])/[HClO]
Given [HClO] = 0.016 M
Ka = 1.01 × 10^-8

Let x be the concentration of H+ ions produced be ionization of HClO.
Then, [H+] = x M
[ClO-] = x M
Using the equilibrium constant expression, we get:
1.01 × 10^-8 = (x^2)/0.016
x^2 = 1.616 × 10^-10
x = 1.27 × 10^-5
Therefore, pH = -log[H+] = -log(1.27 × 10^-5) = 4.90
Since pH of a strong acid like HCl is in the range of 0 to 1, and the pH of the given solution is much higher than that, we can conclude that the solution is not acidic, and must be basic or neutral. HClO is an oxyacid of chlorine, and its conjugate base, ClO- is a weak base. When dissolved in water, some of the HClO ionizes to H+ and ClO-. The H+ ions react with the water molecules to form H3O+ ions, and the ClO- ions react with the H3O+ ions to form H2O and Cl-. Therefore, the solution will be basic. The pH of a basic solution is greater than 7. Option D, with a pH value of 1.80 is incorrect. We can eliminate option A and B, as the pH value should be higher than 7. Option C, with a pH value of 12.20 is too high for a solution that is formed by a weak acid. Therefore, the correct option is D, with a pH value of 4.90.

What Is the PH of a 0 ∘\circ∘ C? (Kw = 1

What Is the PH of a 0 $\circ$ C? (K_w = 1