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Properties such as boiling point, freezing point and vapour, pressure of a pure solvent change Propeties 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 mixtureas anti-freezing liquid in the radiator of automobiles. A solution M is prepared by mixing athanol and water. The mole fraction of ethanol in the mixture is 0.9 GivenFreezing 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 kg "mol"^(-1) Boiling point elevation constant of ethanol (K_(b)^("ethanol"))=1.2 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 tandard boiling point of ethanol =351.5 K Vapour pressure of pure water =32.8 mmHg Vapour presure of pure ethanol =40g Hg Molecular weight of water =18 g"mol"^(-1) Molecules 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. 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 mixtureas anti-freezing liquid in the radiator of automobiles. A solution M is prepared by mixing athanol and water. The mole fraction of ethanol in the mixture is 0.9 GivenFreezing 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 kg "mol"^(-1) Boiling point elevation constant of ethanol (K_(b)^("ethanol"))=1.2 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 tandard boiling point of ethanol =351.5 K Vapour pressure of pure water =32.8 mmHg Vapour presure of pure ethanol =40g Hg Molecular weight of water =18 g"mol"^(-1) Molecules 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

Answer»

`268.7 K`
`268.5 K`
`234.2 K`
`150.9 K`

SOLUTION :`DeltaT_(F)=K_(t)xxm`
`2xx(0.1)/(0.9xx46)xx100=4.83K`
FREEZING point of solution `M=155.7-4.83=150.87 K=150.9K`


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