Question

An aqueous solution ethanol has density $1.025gm{L}^{-1}$ and $2M$. What is the molality of this solution?

• A. $1.79m$
• B. $2.143m$
• C. $1.951m$
• D. None of these

Answer 1

The correct option is B $2.143m$

$1000mL\text{solution contain 2 mole of ethanol or}1000\times 1.025g\text{solution contain 2 mole of ethanol}\text{weight of solvent}=1000\times 1.025-2\times 46$
$m=\frac{2}{1000\times 1.025-2\times 46}\times 1000m=\frac{2}{933}\times 1000=2.143m$