Question

If $5.85g$ of $NaCl$ are dissolved in $90g$ of water, the mole fraction of solute is ____________.

• A. $0.0196$
• B. $0.01$
• C. $0.1$
• D. $0.2$

Answer 1

The correct option is A $0.0196$

Given:-

Mass of $NaCl=5.85g$

Mass of $H_{2}O=90g$

Number of moles of $NaCl=\frac{5.85}{58.5}=0.1$

Number of moles of $H_{2}O=\frac{90}{18}=5$

Mole fraction of solute= $\frac{n_{\text{solute}}}{n_{\text{solute}}+n_{\text{solvent}}}$

Mole fraction= $\frac{0.1}{5+0.1}$

$\Rightarrow X_B=0.0196$

Hence, the correct option is $A$