Question

Calculate the percent ionization of 0.130 M lactic acid (Ka=1.4×10−4). Calculate the percent ionization of 0.130 M lactic acid in a solution containing 7.0×10−3 M sodium lactate. Calculate the pH of a buffer that is 0.200 M in NaHCO3 and 0.280 M in Na2CO3. Calculate the pH of a solution formed by mixing 65 mL of 0.35 M NaHCO3 with 75 mL of 0.23 M Na2CO3.

Answer 1

a)

[H+] = sqrt (Ka x C)

       = sqrt (1.4 x 10^-4 x 0.130)

      = 4.27 x 10^-3 M

% ionization = [H+] / C ) x 100

                    = (4.27 x 10^-3 / 0.130) x 100

% ionization = 3.28 %

b)

pH = pKa + log [salt / acid]

    = 3.85 + log [7 x 10^-3 / 0.130]

   = 2.58

[H+] = 2.63 x 10^-3 M

% ionization = (2.63 x 10^-3 / 0.130) x 100

                    = 2.02 %