What Mass of NaF Must Be Added to 50

Multiple Choice

What mass of NaF must be added to 50.0 mL of a 0.500 M HF solution to achieve a pH of 3.25? For HF, K_a = 7.2 × 10⁻⁴.

A) 1.3 g
B) 0.69 g
C) 6.9 g
D) 23 g
E) 1.5 g