The ionzation constant of formic acid is $ 7.8 \times 10 ^{-4 }. Calculate ratio of sodium formate & formic acid in a buffer of P^H 4.25 $
$ pka = -log ( 1.8 \times 10 ^ {-4} ) = 3.74 $ $ log { [salt ] \over [acid] } = P^H - pka = 4.25 - 3.74 = 0.51 $ $ \therefore { [salt] \over [acid] } = antilog of 0.51 = 3.24 $