Buffer Solutions
Recall that a solution of 1.00 M HF and 0.500 M NaF has a pH of 2.854
Now add 0.100 M HCl (assume there is no volume change)
To find the new pH, first assume that all the added strong acid reacts to change the F- and HF concentrations.
[HF] = 1.00 + 0.100 = 1.100 M
[F-] = 0.500 - 0.100 = 0.400 M