Properties such as boiling point, freezing point and vapour pressure of a pure solvent change
Channel: Doubtnut
Date: 2020-08-02

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. Thus moel fraction of ethanol in the mixture is `0.9`.   Given: Freezing point depression constant of water   `(K_(f)^("water")) = 1.86 K kg mol^(-1)`   Freezing point depression constant of ethanol   `(K_(f)^("ethanol")) = 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)^("ethanol")) = 1.2 K kg mol^(-1)`   Standard freezing point of water `= 273 K`   Standard freezing point of ethanol `= 155.7K`   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`   Molecualr weight of water `= 18 g mol^(-1)`   Molecular weight of ethanol `= 46 g mol^(-1)`   In asweering the following questions, consider the solutions to be ideal dilute solutions and solutes to be non-volatile and non-dissociative.   The freezing point of the solution `M` is :