Properties such as boiling point, freezing point and vapour pressure of a pure solvent…

Properties such as boiling point, freezing point and vapour pressure of a pure solvent change when solute molecules are added to get homogeneous solution. These are called colligative properties. Applications of colligative properties are very useful in day-to-day life. One of its examples is the use of ethylene glycol and water mixture as anti-freezing liquid in the radiator of automobiles.

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

Given, Freezing point depression constant of water

\(\left(\mathrm{k}_{\mathrm{f}}^{\text {water }}\right)=1.86 \mathrm{~K} \mathrm{~kg} \mathrm{~mol}^{-1}\)

Freezing point depression constant of ethanol

\(\left(\mathrm{k}_{\mathrm{f}}^{\text {ethanol }}\right)=2.0 \mathrm{~K} \mathrm{~kg} \mathrm{~mol}^{-1}\)

Boiling point elevation constant of water

\(\left(\mathrm{k}_{\mathrm{b}}^{\text {water }}\right)=0.52 \mathrm{~K} \mathrm{~kg} \mathrm{~mol}^{-1}\)

Boiling point elevation constant of ethanol

\(\left(\mathrm{k}_{\mathrm{b}}^{\text {ethanol }}\right)=1.2 \mathrm{~K} \mathrm{~kg} \mathrm{~mol}^{-1}\)

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 \(=32.8 \mathrm{~mm} \mathrm{Hg}\) 

Vapour pressure of pure ethanol \(=40 \mathrm{~mm} \mathrm{Hg}\) 

Molecular weight of water \(=18 \mathrm{~g} \mathrm{~mol}^{-1}\)

Molecular weight of ethanol \(=46 \mathrm{~g} \mathrm{~mol}^{-1}\)

In answering the following questions, consider the solutions to be ideal dilute solutions and solutes to be non-volatile and non-dissociative. (2008)