Question

$8$g of $NaOH$ is dissolved in $18$g of $H_{2}O$. Mole fraction of $NaOH$ in solution and molality (in mol $k{g}^{-1}$) of the solutions respectively are:

• A. $0.167,11.11$
• B. $0.2,22.20$
• C. $0.2,11.11$
• D. $0.167,22.20$

Answer 1

The correct option is A $0.167,11.11$

$8$g $NaOH$, mol of $NaOH$ $=\frac{8}{40}=0.2$mol

$18$g of $H_{2}O$, mol of $H_{2}O=\frac{18}{18}=1$ mol

$\therefore X_{NaOH}=\frac{0.2}{1.2}=0.167$

Molality $=\frac{0.2\times 1000}{18}=11.11$m.

Hence, the correct option is $A$