Suppose 5 g of ${\mathrm{CH}}_3\mathrm{COOH}$ is dissolved in one litre of Ethanol. Assume no reaction between them. Calculate molality of resulting solution if density of ethanol is 0.789 g/ml.

Weight of ${\mathrm{CH}}_3\mathrm{COOH}$ dissolved = 5 g

Moles of ${\mathrm{CH}}_3\mathrm{COOH}$ dissolved $=\frac{5}{60}$

Volume of ethanol = 1 litre = 1000 ml.

$\therefore$ Weight of ethanol $=1000\times 0.789=789\mathrm{g}$

$\therefore$ Molality of solution 

$\mathrm{m}=\frac{\text{Moles of solute}}{\text{wt. of solvent in kg}}=\frac{\frac{5}{60\times 789}}{1000}=0.1056$