Relative Lowering of Vapour Pressure

IMPORTANT

Relative Lowering of Vapour Pressure: Overview

This topic covers concepts, such as, Relative Lowering of Vapour Pressure, Molecular Mass of a Solute through Relative Lowering of Vapour Pressure & Ostwald and Wacker's Experiment etc.

Important Questions on Relative Lowering of Vapour Pressure

EASY
IMPORTANT

The mass of a non-volatile, non-electrolyte solute (molar mass = 50 g mol-1 ) needed to be dissolved in 114 g octane to reduce its vapour pressure by 75 %, is:

MEDIUM
IMPORTANT

A solution X contains 12 g of urea per litre of water. Another solution Y contains 68.4 g of cane sugar per litre of water at the same temperature. What is the ratio of lowering of vapour pressure in solutions of X and Y?

N=14 u, C=12 u, O=16 u, H=1 u

MEDIUM
IMPORTANT

The vapour pressure of an aqueous solution of cane sugar (molar weight=342) is 756 mm at 100°C. How many grams of sugar are present per 1000 g of water? Report the answer in the nearest integer

MEDIUM
IMPORTANT

What is the vapour pressure of a solution containing 15.6 g of water and 1.68 g of sucrose C12H22O11 at 100° C?

Give your answer by rounding off to the nearest integer value.Molecular weight of sucrose is 342.

MEDIUM
IMPORTANT

The pressure of the water vapour of a solution containing a non-volatile solute is 2% below that of the vapour of pure water. Determine the molality of the solution.

Round off your answer to nearest integer value.

MEDIUM
IMPORTANT

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? (Write the answer without units)

HARD
IMPORTANT

Two beaker are placed in a sealed flask. Beaker A initially contained 0.15 mol of naphthalene (non-volatile) in 117 g of benzene and beaker B initially contained 31 g of an unknown compound (non-volatile, non-electrolytic) in 117 g of benzene. At equilibrium, beaker A is found to have lost 7.8 g of weight. Assume ideal behaviour of both solutions to answer the following question.

The molar mass of solute in solution B is closest to:

EASY
IMPORTANT

Relative vapour pressure lowering depends only on.

EASY
IMPORTANT

Vapour pressure of solution of a non volatile solute is always

EASY
IMPORTANT

Lowering of the vapour pressure of the solution:

EASY
IMPORTANT

Find the value of mole fraction of the solute when vapour pressure of glucose is 750 mm Hg at 373 K in dilute solution.

MEDIUM
IMPORTANT

Find the correct relation between pKa1 and pKa2 of acids HA1 and HA2 (assuming they are taken in same concentration), if lowering of vapour pressure $\Delta \mathrm{P}_{1}$ of an aqueous solution of acid HA1 and $\Delta \mathrm{P}_{2}$ of an aqueous solution of acid HA2, are related as P1>P2.
 

HARD
IMPORTANT

An ideal solution of two pure liquids A and B are having the vapour pressure of 100 and 400 torr respectively at the temperature T. The liquid solution of A and B is made up of 1 mole of each A and B. Then, find the pressure when 1 mole of mixture has been vaporised.

MEDIUM
IMPORTANT

The relative lowering of the vapour pressure of an aqueous solution containing a non-volatile solute is 0.0125. What is the molality of the solution?

MEDIUM
IMPORTANT

A solution of 2.0 g of sulphur in 100 g of CS2 has a vapour pressure of 844.9 torr. At 48oC, the vapour pressure of pure CS2 is 850 torr. Calculate the atomicity of sulphur molecule.

HARD
IMPORTANT

If two beaker A and B are present in a closed vessel. Beaker A contains152.4 g aqueous solution of urea, containing12 g of urea. Beaker B contains 196.2 g glucose solution, containing 18 g of glucose. Both solutions allowed to attain the equilibrium. Calculate the Weight% of glucose in its solution at equilibrium.

MEDIUM
IMPORTANT

The vapor pressure of pure  water (Po) is 17.5mm of Hg at 20°C. Calculate the vapor pressure of the resulting solution (Ps)  when 18g of glucose is added to 178.2g of water?

EASY
IMPORTANT

Assertion : When dry air is passed continuously through an aqueous solution of a non-volatile solute, vapour pressure of solution decreases gradually.

Reason : Some air is absorbed in the solution.

EASY
IMPORTANT

The vapour pressure of water at 20°C is 17.5 mm of Hg. If 18 g of glucose C6H12O6 is added to 178.2 g of water at 20C, what will be the vapour pressure of the resulting solution?