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Separation of Components of a Mixture

For the depre...

Question

For the depression of freezing point experiment with non-volatile solute the correct statement(s) is/are

vapour pressure of pure solvent is more than that of solution

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vapour pressure of pure solvent is less than that of solution

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only solute molecules solidify at the freezing point

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only solvent molecules solidify at the freezing point

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Solution

The correct options are
A vapour pressure of pure solvent is more than that of solution
D only solvent molecules solidify at the freezing point

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Similar questions

Q. A solvent X freezes at

240^{\circ} C

. If

0.25

molal solution of a non volatile solute in pure X causes freezing point depression of

3^{\circ} C

, then

K_{f}

(in

{K kg mol}^{- 1}

) for solvent X is:

Assume complete association/dissociation of solute.

Q. Read the passage given below and answer the following questions:
A soluble solid in solution has the effect of raising its boiling point and depressing its freezing point. The addition of non-volatile substances to a solvent decreases the vapor pressure and the added solute particles affects the formation of pure solvent crystals. According to many researches the decrease in freezing point directly correlated to the concentration of solutes dissolved in the solvent. This phenomenon is expressed as freezing point depression and it is useful for several applications such as freeze concentration of liquid food and to find the molar mass of an unknown solute in the solution. Freeze concentration is a high quality liquid food concentration method where water is removed by forming ice crystals. This is done by cooling the liquid food below the freezing point of the solution.
When a non-volatile solid is added to pure water it will

Q. Given that,

Δ T_{f}

is the depression in freezing point of the solvent in a solution of a non-volatile non-electrolytic solute of molality m, then quantity -

lim m \to 0 (Δ T_{f} / m)

is ___ (equal\different) to molal depression constant.

Q. If the elevation in boiling point of a solution of non-volatile, non-electrolytic and non-associating solute in a solvent

(K_{b} = x K k g m o l^{- 1})

y K

, then the depression in freezing point of solution of same concentration would be:

[K_{f}

of the solvent

= z K k g m o l^{- 1}]

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. The mole fraction of ethanol in the mixture is 0.9.

Given, freezing point depression constant of water

$(K_{f}^{w a t e r}) = 1.86 K k g m o l^{- 1}$

Freezing point depression constant of ethanol

$(K_{b}^{w a t e r}) = 2.0 K k g m o l^{- 1}$

Boiling point elevation constant of water

$(K_{b}^{w a t e r}) = 0.52 K k g m o l^{- 1}$

Boiling point elevation constant of ethanol

$(K_{b}^{e t h a n o l}) = 1.2 K k g m o l^{- 1}$

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 = 351.5K

Vapour pressure of pure water = 32.8 mm Hg

Vapour pressure of pure ethanol = 40 mm Hg

Molecular weight of water $= 18 g m o l^{- 1}$

Molecular weight of ethanol $= 46 g m o l^{- 1}$

In answering the following questions, consider the solutions to be ideal dilute solutions and solutes to be non-volatile and non-dissociative.

The vapour pressure of the solution M is

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For the depression of freezing point experiment with non-volatile solute the correct statement(s) is/are

The correct options are A vapour pressure of pure solvent is more than that of solution D only solvent molecules solidify at the freezing point

The correct options are
A vapour pressure of pure solvent is more than that of solution
D only solvent molecules solidify at the freezing point