The correct answer is 2.73.
HF is a weak acid which partially dissociates to release H+ and F-
HF → H⁺ + F⁻
Initial 0.0050 0 0
Change -x +x +x
Equilibrium 0.0050–x +x +x
Solve by using the equilibrium expression: = [H⁺] [F⁻]/ [HF]
6 .8 x 10⁻⁴= x. x / 0.0050 –x
6 .8 x 10⁻⁴= x² /0.0050
x² = 6 .8 x 10⁻⁴ x 0.0050
x² = 3.4 x 10⁻⁶
x = 3.4 x 10⁻⁶
[H⁺] = 1.84 x 10⁻³
pH = - log [H⁺] = - log (1.84 x 10⁻³)
pH = 2.73
