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Q.
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
Concentration of calcium lactate $=0.005 \,M$,: concentration of lactate ion $=(2 \times 0.005)\, M$. Calcium lactate is a salt of weak acid $+$ strong base $\therefore$ Salt hydrolysis will take place.
$ pH =7+\frac{1}{2}( pKa +\log C ) $
$ =7+\frac{1}{2}(5+\log (2 \times 0.005))$
$ =7+\frac{1}{2}[5-2 \log 10]=7+\frac{1}{2} \times 3=8.5=85 \times 10^{-1}$
