Some properties 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 useful in day-to day life. 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 kg mol"^(-1) Freezing point depression constant of ethanol(K_(f)^("ethanol"))=2.0"K kg mol"^(-1) Boiling point elevation 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 = 155.7 K Standard boiling point of water = 373 K Standard boiling point of ethanol = 251.5 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. The freezing point of the solution M is