What is the pH of a 0127 M solution of the salt NaF The ioni

What is the pH of a 0.127 M solution of the salt NaF? The ionization constant of the weak acid HF is 6.7 × 10−4.

Answer in units of pH.

Solution

NaF is a strong salt : NaF => Na+ + F- and,

F- + H2O <-----> HF + OH- .Now,

Kb = Kw/ Ka = (1.0 x 10^-14 / 6.7 x 10^-4 ) = 1.49 x 10^-11

1.49 x 10^-11 = x^2 / 0.14-x Implies,

x = [OH-]= 1.49 x 10^-6 M.Thus,

pOH = - log [OH-]= 5.9. Thus,

pH = 14 - pOH = 14 - 5.9=8.1

I hope this will help.