Question

If the $pKa$ of lactic acid is $5$ , then the $pH$ of $0.005 \,M$ calcium lactate solution at $25^{\circ} C$ is ______ $\times 10^{-1}$ (Nearest integer) Lactic acid

Answer 1

The correct answer is 85.
Concentration of calcium lactate =0.005M,: concentration of lactate ion =(2×0.005)M. Calcium lactate is a salt of weak acid + strong base ∴ Salt hydrolysis will take place.
pH=7+21​(pKa+logC)
=7+21​(5+log(2×0.005))
=7+21​[5−2log10]=7+21​×3=8.5=85×10−1