To 100 mL of 0.10 M acetic acid, V mL of 0.10 M NaOH is added so that pH = $p K_{a} - 0.301$ ( $lo g 2 = 0.301$ ). Find V in mL, to one decimal place.

Numerical answer type, answer in mL, tolerance 0.3.

Answer: 33.3333 mL

Acid = 10 mmol. NaOH = x mmol gives salt = x, acid = 10 - x with x/(10 - x) = 1/2, so x = 3.333 mmol. V = 3.333/0.10 = 33.3 mL.