Karnataka Board PUCPUC Science 2nd PUC Class 12

State Raoult’S Law for the Solution Containing Volatile Components - Chemistry


State Raoult’s law for the solution containing volatile components



Raoult’s law: In a solution, the vapour pressure of a component at a given temperature is equal to the mole fraction of that component in the solution multiplied by the vapour pressure of that component in the pure state.

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2014-2015 (March) Panchkula Set 1


In non-ideal solution, what type of deviation shows the formation of maximum boiling azeotropes?

What is meant by positive deviations from Raoult's law? Give an example. What is the sign of ∆mixH for positive deviation?

Define azeotropes. 

Why does a solution containing non-volatile solute have higher boiling point than the pure solvent ?

What type of deviation is shown by a mixture of ethanol and acetone ? Give reason.

Vapour pressure of pure water at 298 K is 23.8 mm Hg. 50 g of urea (NH2CONH2) is dissolved in 850 g of water. Calculate the vapour pressure of water for this solution and its relative lowering.

What is meant by positive and negative deviations from Raoult's law and how is the sign of ΔsolH related to positive and negative deviations from Raoult's law?

An aqueous solution of 2% non-volatile solute exerts a pressure of 1.004 bar at the normal boiling point of the solvent. What is the molar mass of the solute?

The vapour pressure of water is 12.3 kPa at 300 K. Calculate vapour pressure of 1 molal solution of a non-volatile solute in it.

Calculate the mass of a non-volatile solute (molar mass 40 g mol−1) which should be dissolved in 114 g octane to reduce its vapour pressure to 80%.

A solution containing 30 g of non-volatile solute exactly in 90 g of water has a vapour pressure of 2.8 kPa at 298 K. Further, 18 g of water is then added to the solution and the new vapour pressure becomes 2.9 kPa at 298 K. Calculate:

(1) molar mass of the solute

(2) vapour pressure of water at 298 K.

Vapour pressure of pure acetone and chloroform at 328 K are 741.8 mm Hg and 632.8 mm Hg respectively. Assuming that they form ideal solution over the entire range of composition, plot ptotalpchloroform’ and pacetone as a function of xacetone. The experimental data observed for different compositions of mixture is.

100 ×xacetone 0 11.8 23.4 36.0 50.8 58.2 64.5 72.1
pacetone /mm Hg 0 54.9 110.1 202.4 322.7 405.9 454.1 521.1
pchloroform/mm Hg 632.8 548.1 469.4 359.7 257.7 193.6 161.2 120.7

What type of azeotrope is formed by positive deviation from Raoult's law ? Give an example.

For the reaction :

\[\ce{2NO_{(g)} ⇌ N2_{(g)} + O2_{(g)}}\];

ΔH = -heat

K= 2.5 × 10at 298K

What will happen to the concentration of Nif :

(1) Temperature is decreased to 273 K.

(2) The pressure is reduced

Match the following:

(i) Colligative property (a) Polysaccharide
(ii) Nicol prism (b) Osmotic pressure
(iii) Activation energy (c) Aldol condensation
(iv) Starch (d) Polarimeter
(v) Acetaldehyde (e) Arrhenius equation

A solution containing 8.44 g of sucrose in 100 g of water has a vapour pressure 4.56 mm of Hg at 273 K. If the vapour pressure of pure water is 4.58 mm of Hg at the same temperature, calculate the molecular weight of sucrose. 

Define Raoult’s law for the elevation of the boiling point of a solution.

What will be the vapour pressure of a solution containing 5 moles of sucrose (C12H22O11) in 1 kg of water, if the vapour pressure of pure water is 4.57 mm of Hg? [C = 12, H = 1, O = 16]

At equilibrium the rate of dissolution of a solid solute in a volatile liquid solvent is ______.

The boiling point of an azeotropic mixture of water and ethanol is less than that of water and ethanol. The mixture shows ____________.

Two liquids X and Y form an ideal solution. The mixture has a vapour pressure of 400 mm at 300 K when mixed in the molar ratio of 1 : 1 and a vapour pressure of 350 mm when mixed in the molar ratio of 1 : 2 at the same temperature. The vapour pressures of the two pure liquids X and Y respectively are ______.

The correct option for the value of vapour pressure of a solution at 45°C with benzene to octane in a molar ratio of 3 : 2 is ______

[At 45°C vapour pressure of benzene is 280 mm Hg and that of octane is 420 mm Hg. Assume Ideal gas]

A solution of a non-volatile 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/mol. The vapour pressure of rain solution at 298 K is ______ mm Hg.

If the weight of the non-volatile solute urea (NH2–CO–NH2) is to be dissolved in 100 g of water, in order to decrease the vapour-pressure of water by 25%, then the weight of the solute will be ______ g.

The vapour pressure of pure liquid X and pure liquid Y at 25°C are 120 mm Hg and 160 mm Hg respectively. If equal moles of X and Y are mixed to form an ideal solution, calculate the vapour pressure of the solution.

An azeotropic mixture of two liquids will have a boiling point lower than either of the two liquids when it ______.


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