Calculate the pH of the following aqueous solution: 0.66 M HOCl (pK_a = 7.46) A)10.18 B)3.82 C)7.64 D)6.36 E)none of these

Question

Quizplus · Accepted Answer

HOCl is a weak acid, so we can write the dissociation reaction as follows:
HOCl + H2O ⇌ H3O+ + OCl-
The equilibrium constant expression for this reaction would be:
Ka = [H3O+][OCl-]/[HOCl]
Since the concentration of HOCl is given as 0.66 M, we can assume that the initial concentrations of H3O+ and OCl- are both 0. Therefore, we can simplify the equilibrium expression to:
Ka = [H3O+]²/0.66
Solving for [H3O+], we get:
[H3O+]² = Ka x 0.66
[H3O+] = sqrt(Ka x 0.66)
[H3O+] = sqrt(10^-7.46 x 0.66) = 1.79 x 10^-4
Taking the negative logarithm of this value gives us the pH:
pH = -log[H3O+] = -log(1.79 x 10^-4) = 3.82
Therefore, the answer is choice B.

Calculate the PH of the Following Aqueous Solution: 0