What concentration of acetic acid (K_a = 1.80 $\times$10^-⁵)has the same pH as that of 5.33 $\times$ 10^-³M HCl? A)17.2 M B)12.4 M C)1.58 M D)5.33 $\times$10^-³M E)none of these

Question

Quizplus · Accepted Answer

The pH of a 5.33 x 10^-10 M HCl solution is calculated to be 9.27. We can use the equation for the dissociation of acetic acid to find its concentration:

CH3COOH ⇌ CH3COO- + H+

Ka = [CH3COO-][H+] / [CH3COOH]

Assuming that the [H+] from the acetic acid dissociation is equal to the [H+] from the autoionization of water (which is valid for weak acids), we can write:

Ka = [CH3COO-]^2 / [CH3COOH]

We know that Ka for acetic acid is 1.8 x 10^-5. Substituting the given pH of 9.27 (which corresponds to [H+] = 6.8 x 10^-10) and solving for [CH3COOH], we get:

1.8 x 10^-5 = (6.8 x 10^-10)^2 / [CH3COOH]
[CH3COOH] = 1.58 M

What Concentration of Acetic Acid (Ka = 1 ×\times× 10-5)has the Same PH as That of 5

What Concentration of Acetic Acid (K_a = 1 $\times$ 10^-⁵)has the Same PH as That of 5