$1.80 \mathrm{~g}$ of solute A was dissolved in $62.5 \mathrm{~cm}^{3}$ of ethanol and freezing point of the solution was found to be $155.1 \mathrm{~K}$. The molar mass of solute A is ________ g $\mathrm{mol}^{-1}$.
[Given : Freezing point of ethanol is 156.0 K.
Density of ethanol is 0.80 g cm$-$3.
Freezing point depression constant of ethanol is 2.00 K kg mol$-$1]
Answer (integer)
80
Solution
Mass of solvent $=d x v=0.8 \times 62.5=50$ gram <br/><br/>$\Delta T_{f}=k_{f} \times m$<br/><br/>
$$
\begin{aligned}
&0.9=2\left[\frac{1.8 \times 1000}{M_{\text {Solute }} \times 50}\right] \\
&M_{\text {Solute }}=\left(\frac{2 \times 1.8 \times 1000}{0.9 \times 50}\right)=80
\end{aligned}
$$
About this question
Subject: Chemistry · Chapter: States of Matter · Topic: Gas Laws
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