HARD
JEE Main
IMPORTANT
Earn 100

A solution M is prepared by mixing ethanol and water. The mole fraction of ethanol in the mixture is 0.9 . Given

Kf(Water)=1.86 K kg mol-1Kf(Ethanol)=2.0 K kg mol-1Kb(Water)=0.52 K kg mol-1Kb(Ethanol)=1.2 K kg mol-1

Standard freezing point of water =273K

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 mmHg 

Vapour pressure of pure ethanol =40 mmHg 

Molecular weight of water =18 g mol-1

Molecular weight of ethanol=46 g mol-1 

Water is added to the solution M such that the mole fraction of water in solution becomes 0.9. What is the boiling point of this solution?

[Hint: Solute is ethanol and solvent is water]

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Important Questions on Solutions

HARD
JEE Main
IMPORTANT

A solution M is prepared by mixing ethanol and water. The mole fraction of ethanol in the mixture is 0.9

Given,

Kf water=1.86 K kg mol-1Kf ethanol=2.0 K kg mol-1Kb water=0.52 K kg mol-1Kb 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 =351.5 K

Vapour pressure of pure water =32.8 mmHg 

Vapour pressure of pure ethanol =40 mmHg 

Molecular weight of water =18 g mol-1

Molecular weight of ethanol =46 g mol-1

The vapour pressure of the solution M is

HARD
JEE Main
IMPORTANT

A liquid mixture of A and B is placed in a cylinder-and-piston arrangement. The piston is slowly pulled out isothermally, so that the volume of the liquid decreases and that of the vapour increases. At the instant when the quantity of the liquid still remaining is negligibly small, the mole fraction of A in the vapour phase is 0.4 pA0=0.4 atm, pB0=1.2 atm at the temperature in question. Calculate the total pressure at which the liquid has almost evaporated. Assume ideal behaviour.

Give answer after multiplying with 100 and rounding off to the nearest integer value.

MEDIUM
JEE Main
IMPORTANT

A solution of a nonvolatile solute in water freezes at -0.30°C. The vapour pressure of pure water at 298 K is 23.51 mm Hg and Kf for water is 1.86 degree/molal. Calculate the magnitude of change in vapour pressure of this solution in mmHg at 298 K.

Give answer after multiplying with 100 and rounding off to the nearest integer value.