Relative Lowering of Vapour Pressure

Q.

A solution has a 1 : 4 mole ratio of pentane to hexane. The vapour pressure of the pure hydrocarbons at 20°Care 440mmHg for pentane and 120mm Hg for hexane. The mole fraction of pentane in the vapour phase would be:

1. 0.549

2. 0.200

3. 0.786

4. 0.478

Q.

The relative lowering of the vapour pressure is equal to the ratio between the number of:

1. Solute moleules and solvent molecules
2. Solute molecules and the total molecules in the solution
3. Solvent molecules and the total molecules in the solution
4. Solvent molecules and the total number of ions of the solute

Q.

An aqueous solution of methanol in water has vapour pressure:

1. Equal to that of water

2. More than that of water

3. Less than that of water

4. Equal to that of methanol

Q. Calculate the mass of urea required to be dissolved in $100g$ of water, so as the vapour pressure of the solution decreases by $50\%$.
Given: $\text{Molecular mass of urea is}60gmo{l}^{-1}$

1. $222.22g$
2. $22.22g$
3. $333.33g$
4. $33.33g$

Q.

Vapour pressure of a solution of 5g of non-electrolyte in 100g of water at a particular temperature is 2985 N/m². The vapour pressure of pure water is 3000 N/m². The molecular weight of the solute is:

1. 120

2. 180

3. 380

4. 60

Q.

Vapour pressure of CCl₄ at 25⁰C is 143mm of Hg. 0.5 gm of a non-volatile solute (mol. wt. = 65) is dissolved in 100ml CCl₄. Find the vapour pressure of the solution (Density of CCl₄=1.58g/cm²)

1. 199.34 mm

2. 141.43 mm

3. 143.99 mm

4. 94.39 mm

Q.

Which of the following solution in water possesses the lowest vapour pressure:

1. 0.1(N)BaCl₂

2. 0.1(M)KCl

3. None of these

4. 0.1(M)NaCl

Q. 5 cm³ of acetone is added to 100cm³ of water, the vapour pressure of water over the solution

1. It will be less than the vapour pressure of pure water
2. It will be equal to the vapour pressure of pure water
3. It will be greater than the vapour pressure of pure water
4. It will be very large

Q.

If P⁰ and P are the vapour pressure of a solvent and its solution respectively and N₁ and N₂ are the mole fractions of the solvent and solute respectively, then correct relation is

1. 

2. 

3. 

4. 

Q.

The relative lowering of vapour pressure produced by dissolving 71.5 g of a substance in 1000 g of water is 0.00713. The molecular weight of the substance will be:

1. 180

2. 18.0

3. 342

4. 60