Calcium lactate is a salt of weak acid and represented as `Ca(LaC)_(2)`. A saturated solution of `Ca(LaC)_(2)` contains `0.13` mole of salt in `0.50` litre solution. The pOH of this is `5.60`. Assuming complete dissociation os salt, calculate `K_(a)` of lactic acid.

Explanation

We have, for the salts of weak acids and strong bases,
`pH =1/2 (pK_(w)+pK_(a)+log a)`,
where a is the concentration of lactate ions, i.e, `(2 xx 0.26)` mole per litre.
`(14-5.6) =1/2 (14-log K_(a)+log 0.52)`
`log K_(a)=-3.084 =bar 4.916`
Taking antilog
`K_(a)=8.24 xx 10^(-4)`