Embibe Experts Solutions for Chapter: Solutions, Exercise 3: Level 3

The relative lowering of vapour pressure of an aqueous solution of urea is $0.018$. If ${\mathrm{K}}_{\mathrm{b}}$ for ${\mathrm{H}}_2\mathrm{O}$ is $0.54 °\mathrm{C} {\mathrm{m}}^{-1},$ the elevation in boiling point will be:

Insulin ${\left({\mathrm{C}}_2{\mathrm{H}}_{10}{\mathrm{O}}_5\right)}_{\mathrm{n}}$ is dissolved in a suitable solvent and the osmotic pressure ($\mathrm{\pi }$) of solutions of various concentrations $\mathrm{C}\left(\mathrm{in} \mathrm{g}/{\mathrm{cm}}^3\right)$ is measured at $20°\mathrm{C}$. The slope of a plot of $\mathrm{\pi }$ against$\mathrm{C}$ is found to be $4.65\times {10}^{-3}$. The molar mass of the insulin is

At $300 \mathrm{K}$, vapour pressure of substance $\mathrm{A}$ is $0.95 \mathrm{atm}$ and vapour pressure of substance $\mathrm{B}$ is $0.15 \mathrm{atm}$. A solution of $\mathrm{A}\text{ and} \mathrm{B}$is prepared and allowed to equilibrate with its vapour. The vapour is found to have equal moles of $\mathrm{A} \text{and} \mathrm{B}$. What is lhe mole fraction of $\mathrm{A}$ in the original solution?

Which of the following relations is correct for the mole fraction of the solute $\left(\mathrm{x}\right) ?$ ($\mathrm{m}$ and $\mathrm{M}$  are the molality of the solution and molar mass of the solvent respectively.)

A solution M is prepared by mixing ethanol and water. The mole fraction of ethanol in the mixture is $0.9 .$ Given

$\begin{array}{l}{\mathrm{K}}_{\mathrm{f}}\left(\mathrm{Water}\right)=1.86 \mathrm{K} \mathrm{kg} {\mathrm{mol}}^{-1}\\ {\mathrm{K}}_{\mathrm{f}}\left(\mathrm{Ethanol}\right)=2.0 \mathrm{K} \mathrm{kg} {\mathrm{mol}}^{-1}\\ {\mathrm{K}}_{\mathrm{b}}\left(\mathrm{Water}\right)=0.52 \mathrm{K} \mathrm{kg} {\mathrm{mol}}^{-1}\\ {\mathrm{K}}_{\mathrm{b}}\left(\mathrm{Ethanol}\right)=1.2 \mathrm{K} \mathrm{kg} {\mathrm{mol}}^{-1}\end{array}$

Standard freezing point of water $=273\mathrm{K}$

Standard freezing point of ethanol $=155.7 \mathrm{K}$

Standard boiling point of water $=373 \mathrm{K}$

Standard boiling point of ethanol $=351.5 \mathrm{K}$

Vapour pressure of pure water $=32.8 \mathrm{mmHg}$ 

Vapour pressure of pure ethanol $=40 \mathrm{mmHg}$ 

Molecular weight of water $=18 \mathrm{g} {\mathrm{mol}}^{-1}$

Molecular weight of ethanol$=46 \mathrm{g} {\mathrm{mol}}^{-1}$ 

Water is added to the solution M such that the mole fraction of water in solution becomes 0.9. What is the boiling point of this solution?

[Hint: Solute is ethanol and solvent is water]

A solution $\mathrm{M}$ is prepared by mixing ethanol and water. The mole fraction of ethanol in the mixture is $0.9$. 

Given,

$\begin{array}{l}{\mathrm{K}}_{\mathrm{f}} \left(\mathrm{water}\right)=1.86 \mathrm{K} \mathrm{kg} {\mathrm{mol}}^{-1}\\ {\mathrm{K}}_{\mathrm{f}} \left(\mathrm{ethanol}\right)=2.0 \mathrm{K} \mathrm{kg} {\mathrm{mol}}^{-1}\\ {\mathrm{K}}_{\mathrm{b}} \left(\mathrm{water}\right)=0.52 \mathrm{K} \mathrm{kg} {\mathrm{mol}}^{-1}\\ {\mathrm{K}}_{\mathrm{b}} \left(\mathrm{ethanol}\right)=1.2 \mathrm{K} \mathrm{kg} {\mathrm{mol}}^{-1}\end{array}$

Standard freezing point of water $=273 \mathrm{K}$

Standard freezing point of ethanol $=155.7 \mathrm{K}$

Standard boiling point of water $=373 \mathrm{K}$

Standard boiling point of ethanol $=351.5 \mathrm{K}$

Vapour pressure of pure water $=32.8 \mathrm{mmHg}$ 

Vapour pressure of pure ethanol $=40 \mathrm{mmHg}$ 

Molecular weight of water $=18 \mathrm{g} {\mathrm{mol}}^{-1}$

Molecular weight of ethanol $=46 \mathrm{g} {\mathrm{mol}}^{-1}$

The vapour pressure of the solution $\mathrm{M}$ is

A liquid mixture of $\mathrm{A}$ and $\mathrm{B}$ is placed in a cylinder-and-piston arrangement. The piston is slowly pulled out isothermally, so that the volume of the liquid decreases and that of the vapour increases. At the instant when the quantity of the liquid still remaining is negligibly small, the mole fraction of $\mathrm{A}$ in the vapour phase is$0.4$ ${\mathrm{p}}_{\mathrm{A}}^0=0.4 \mathrm{atm}, {\mathrm{p}}_{\mathrm{B}}^0=1.2 \mathrm{atm}$ at the temperature in question. Calculate the total pressure at which the liquid has almost evaporated. Assume ideal behaviour.

Give answer after multiplying with 100 and rounding off to the nearest integer value.

A solution of a nonvolatile solute in water freezes at $-0.30°\mathrm{C}$. The vapour pressure of pure water at $298 \mathrm{K}$ is $23.51 \mathrm{mm} \mathrm{Hg}$ and ${\mathrm{K}}_{\mathrm{f}}$ for water is $1.86 \mathrm{degree}/\mathrm{molal}$. Calculate the magnitude of change in vapour pressure of this solution $\left(\mathrm{in} \mathrm{mmHg}\right)$ at $298 \mathrm{K}$.

Give answer after multiplying with 100 and rounding off to the nearest integer value.