Calculate [H+] for a 1.20×10-3 M aqueous solution of acetic acid (HC2H3O2; Ka = 1.80×10-5).
b) Calculate the pH of the above solution
Let's call HC2H3O2 simply HAc, then
......................HAc --> H^+ + Ac^-
I................0.00120........0........0
C.....................-x............x.........x
E...............0.00120-x.......x........x
Ka = 1.8E-5 = (x)(x)/(0.00120-x)
Solve for x = (H^+) = (Ac^-) and convert to pH . See below.
For part b pH = -log(H^+)
Post your work if you get stuck.