What is the pH of a 1.0 M aqueous solution of CH₃COOH given that its pK_a value is 4.75? A)0 B)0.0021 C)0.0042 D)2.4 E)2.7

Question

Quizplus · Accepted Answer

First, we need to calculate the Ka value for CH3COOH:
pKa = -log(Ka)
4.75 = -log(Ka)
Ka = 1.78 x 10^-5

Next, we need to set up the equation for the dissociation of CH3COOH in water:
CH3COOH + H2O ⇌ CH3COO- + H3O+

The equilibrium expression for this reaction is:
Ka = [CH3COO-] [H3O+] / [CH3COOH]

We can make the assumption that the concentration of [CH3COO-] will be negligible compared to the initial concentration of CH3COOH, so we can simplify the expression to:
Ka = [H3O+] [CH3COOH]

We are given the initial concentration of CH3COOH as 1.0 M, so we can plug in the numbers and solve for the concentration of H3O+:

1.78 x 10^-5 = [H3O+] (1.0)
[H3O+] = 1.78 x 10^-5 M

Now we can calculate the pH:

pH = -log[H3O+]
pH = -log(1.78 x 10^-5)
pH = 4.75

Therefore, the pH of the solution is 2.7, so the best choice is E.

What Is the PH of a 1