Question

Hom many grams of $KOH$ must be dissolved in one litre of solution given its $pH$ of $12$?

Answer 1

$i)$ $pH$ is $12$.

$\therefore pH+pOH=14pOH=14-12=2$

$pOH=-\log \left[O\overline{H}\right]2=-\log \left[\overline{O}H\right]\therefore \left[\overline{O}H\right]=Al\left[\overline{2}\right]={10}^{-2}=0.01M$

$0.01$ Mol of $\overline{O}H$ ion will be obtained from $0.01$ mol of $KOH.$

$ii)$ $\text{moles}=\frac{\text{Weights in gram}}{\text{molecular weight of}KOH}⟹0.01=\frac{w}{56.1}$

$\therefore w=0.01\times 56.1=0.56grams$