Question

Explain hydrolysis, i.e, what types of molecules undergo hydrolysis (be specific) and show equations for reactions of acid, base, and salt hydrolysis You prepare a buffer by adding 10.0 mL of 0.10 M acetic acid and 10.0 mL of 0.10 M sodium acetate.

Calculate the pH that you expect for this buffer. Write the chemical equation for the equilibrium. Show your work using an ICE table. To the solution from #4, you add 0.50 mL of 0.10 M HCl. Calculate the new pH of the buffer solution.

Write the chemical equations for the reaction and the equilibrium. Show your work using an ICE table. To the solution from #4, you add 0.50 mL of 0.10 M NaOH. Calculate the new pH of the buffer solution. Write the chemical equation for the equilibrium. Show your work using an ICE table.

Answer 1

millimoles of acetic acid = 10 x 0.1 = 1

millimoles of sodium acetate = 10 x 0.1 = 1

CH3COOH + NaOH ----------------> CH3COONa + H2O

     2                   1    0    0   -------------   initial

    -1                    -1 +1 +1 ------------ change

    1                       0                                      1                 1   ------------- equilibrium

pH = pKa + log [salt / acid]

      = 4.74 + log [sodium acetate / acetic acid]

      = 4.74 + log (1/1)

pH = 4.74

2)

millimoles of HCl added = 0.5 x 0.1 = 0.05 (C)

pH = pKa + log [salt - C / acid + C]

      = 4.74 + log [1 - 0.05 / 1 + 0.05]

pH = 4.70

millimoles of NaOH added = 0.50 x 0.1 = 0.05

pH = pKa + log [salt + C / acid - C]

      = 4.74 + log [1 + 0.05 / 1 - 0.05]

      = 4.78

pH = 4.78