$6 \mathrm{~g}$ of a non-volatile solute $(\mathrm{x})$ is dissolved in $100 \mathrm{~g}$ of water. The relative lowering of vapour pressure of resultant solution is 0.006 . What is the molar mass (in $\mathrm{g} \mathrm{mol}^{-1}$ ) of $\mathrm{x}$ ?

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Aicharya · Accepted Answer

$\begin{aligned} & 	ext {} \frac{\Delta \mathrm{P}}{\mathrm{P}^0}=0.006, \mathrm{~m}_1=100 \mathrm{~g}, \mathrm{~m}_2=6 \mathrm{~g}, \mathrm{M}_1=18.0 \mathrm{~g} \mathrm{~mol}^{-1} \ & \frac{\Delta \mathrm{P}}{\mathrm{P}^0}=\mathrm{x}_2=\frac{\mathrm{n}_2}{\mathrm{n}_1+\mathrm{n}_2} \cong \frac{\mathrm{n}_2}{\mathrm{n}_1}\left(\mathrm{n}_1 \gg \mathrm{n}_2ight) \ & \Rightarrow \mathrm{n}_2=\frac{\Delta \mathrm{P}}{\mathrm{P}^0} 	imes \mathrm{n}_1=0.006 	imes \frac{100.0}{18.0}=0.0334 \ & \Rightarrow \mathrm{M}_2=\frac{\mathrm{m}_2}{\mathrm{n}_2}=\frac{6.0}{0.0334} \cong 180 \mathrm{~g} \mathrm{~mol}^{-1}\end{aligned}$

$6 \mathrm{~g}$ of a non-volatile solute $(\mathrm{x})$ is dissolved in $100 \mathrm{~g}$ of water. The…

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