A 1.00 L buffer solution is 0.250 M in HC2H3O2 and 0.250 M in NaC2H3O2. Calculate the pH of the solution after the addition of 0.150 mol of solid NaOH. Assume no volume change upon the Additon o f NaOH. The Ka value for HC2H3O2 at 25 C is 1.8 x 10^-5.

Answer 1

HC2H3O2 = HAc
NaC2H3O2 = NaAc
millimols HAc = mL x M = approx 250
mmols NaAc = 250
0.150 mol NaOH = 150 mmol

......HAc + OH^- ==> Ac^- + H2O
I.....250....0.......250.......
add........150.................
C...-150..-150.......+150
E.....100...0........400

Plug the E line into the HH equation and solve for pH.