Which of the following when added to a 1.0 L solution containing 0.10 M NaF and 0.20 M HF will result in a solution where pH = pKa for HF? Ka for HF = 7.2 x 104. Show ALL calculations and state your reasoning that led to your answer.
a) 0.050 mol NaOH
b) 0.10 mol NaOH
c) 0.050 mol HCl
d) 0.10 mol HCl
e) 0.20 mol HCl