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 examplesis 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 mixtureis 0.9
Given : Freezing point depression constant of water $$\left(K_{f}^{water}\right)$$ = 1.86 K kg mol$$^{-1}$$
Freezing point depression constant of ethanol $$\left(K_{f}^{ethanol}\right)$$ = 2.0 K kg mol$$^{-1}$$
Freezing point elevation constant of water $$\left(K_{b}^{water}\right)$$ = 0.52 K kg mol$$^{-1}$$
Freezing point elevation constant of ethanol $$\left(K_{b}^{ethanol}\right)$$ = 1.2 K kg mol$$^{-1}$$
Standard freezing point of water = 273 K
Standard freezing point of ethanol = 155.7 K
Standard boiling point of water = 373 K
Standard boiling point of ethanol = 351.5 K
Vapour pressure of pure water = 32.8 mm Hg
Vapour pressure of pure ethanol = 40 mm Hg
Molecular weight of water = 18 g mol$$^{-1}$$
Molecular weight of ethanol = 46 g mol$$^{-1}$$

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