Question

The vapour pressure of a solution containing 2 moles of a solute in 2 moles of water (vapour pressure of pure water =24mm Hg) is

a. 24 mm Hg
b. 32 mm Hg
c. 48 mm Hg
d. 12 mm Hg

Answer 1

Answer - 12mmHg

Explanation: vapour pressure of pure compound = 24 mmHg

Answer 2

Answer:

The vapour pressure of a solution will be 12 mmHg i.e.option (d).

Explanation:

We will use following relation to solve the question,

$P=xP_0$          (1)

Where,

P=vapour pressure of a solution

x=mole fraction

P₀=vapour pressure of pure solvent

From the question we have,

Number of moles of solute(n₁)=2

Number of moles of water(n₂)=2

Vapour pressure of puree water(P₀)=24mmHg

Mole fraction can be calculated as follows,

$x=\frac{n_1}{n_1+n_2}$            (2)

By substituting the required values in equation (2) we get;

$x=\frac{2}{2+2}$

$x=\frac{1}{2}$           (3)

By substituting the values of P₀ and x in equation (1) we get;

$P=\frac{1}{2} \times 24$

$P=12mmHg$

Hence, the vapour pressure of a solution will be 12 mmHg i.e.option (d).