A 6.50 molal solution of KOH (aq.) has a density


A $6.50$ molal solution of $\mathrm{KOH}$ (aq.) has a density of $1.89 \mathrm{~g} \mathrm{~cm}^{-3}$. The molarity of the

solution is___________ $\mathrm{mol} \mathrm{dm}^{-3}$. (Round off to the Nearest Integer).

[Atomic masses: $\mathrm{K}: 39.0 \mathrm{u} ; \mathrm{O}: 16.0 \mathrm{u} ; \mathrm{H}: 1.0 \mathrm{u}$ ]


$6.5$ molal $\mathrm{KOH}=1000 \mathrm{gm}$ solvent has

$6.5$ moles $\mathrm{KOH}$

so $\mathrm{wt}$ of solute $=6.5 \times 56$

$=364 \mathrm{gm}$

wt of solution $=1000+364=1364$

Volume of solution $=\frac{1364}{1.89} \mathrm{~m} \ell$

Molarity $=\frac{\text { mole of solute }}{\mathrm{V}_{\text {solution }} \text { in Litre }}$

$=\frac{6.5 \times 1.89 \times 1000}{1364}$


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