Properties such as boiling point, freezing point and vapour pressure of a pure solvent
Channel: Doubtnut
Date: 19/04/2020

Properties such as boiling point, freezing point and vapour pressure of a pure solvent change when solute molecules are added to get homogenous solution. These are called colligative properties. Application of colligative properties are very useful in day-to-day life. One of its example 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 `(K_(f)^("water")) = 1.86 K "mol"^(-1)`   Freezing point depression constant of ethanol `(K_(f)^("ethonal")) = 2.0 K kg "mol"^(-1)`   Boiling point elevation constant of water `(K_(b)^("water")) = 0.52 K kg "mol"^(-1)`   Boiling point elevation constant of ethanol `(K_(b)^("ethonal")) = 1.2 K kg mol^(-1)`   Standard freezing point of water `= 273 K`   Standard freezing point of ethonal `= 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 ethonal `= 40 mm Hg`   Molecular weight of water `= 18 g "mol"^(-1)`   Molecular weight of ethonal `= 45 g"mol"^(-1)`   In answering the following questions, consider the solution to be ideal ideal solutions and solutes to be non-volatile and non-dissociative.   The freezing point of the solution M is :