Question

An unknown liquid 'A' is immiscible with water. It is steam distilled at ${98}^{o}C$ and 737 torr pressure. If $P_{H_{2}O}^0$ is 707 torr at ${98}^{o}C$; the distillate contains 75% by mass of water. Calculate molar mass of liquid in $gmo{l}^{-1}$ (if answer is $140+x$, then find the value of $x$).

Answer 1

Let $P_1^0$ and $P_2^0$ represents the vapor pressures of pure liquid A and pure liquid water respectively.
$P_2^0=707torr$
$P_1^0=737torr-707torr=30torr$
$\frac{w_1}{w_2}=\frac{P_1^0{M}_1}{P_2^0{M}_2}$
$\frac{25}{75}=\frac{30\times M_1}{707torr\times 18g/mol}$
$M_1=141.1g/mol$