a. What is the pH of 0.1 M HCl (strong acid) using a pH meter b. What is the pH of 0.1 M Acetic acid (weak solution) using a pH meter

Question

I just want to double check that I did my solutions correctly

Answer 1

We can calculate the theoretical pH of each solution, and then you'd have to compare that to what you actually observed using the pH meter. Many things can cause the pH of the solution to be slightly different between actual and calculated.

For 0.1 M HCl:

pH = -log [H+] = -log 0.1

pH = 1.0

For 0.1 M acetic acid (CH₃COOH; HAc):

HAc ==> H⁺ + Ac^-

Looking up the Ka for acetic acid, I find it to be 1.76x10^-5

Ka = [H+][A-] /[HA] = (x)(x) / 0.1

1.76x10^-5 = x² / 0.1

x² = 1.76x10^-6

x = [H+] = 1.33x10^-3 M

pH = -log 1.33x10^-3

pH = 2.9