JEE Main · 2021 · 20 Jul 2021 · Shift 2 · Solutions

The vapour pressures of A and B at

2 5^{\circ} C

are 90 mm Hg and 15 mm Hg respectively. If A and

B

are mixed such that the mole fraction of

A

in the mixture is 0.6 , then the mole fraction of

B

in the vapour phase is

x \times 1 0^{- 1}

. The value

x

is ____ . .(Nearest Integer)

Answer: 1

Solution

The mixture is ideal, so each component follows Raoult's law and the total pressure is the sum of the two partial pressures. With

x_{A} = 0.6

and

x_{B} = 0.4

p = 90 (0.6) + 15 (0.4) = 54 + 6 = 60 mm Hg

The mole fraction of a component in the vapour is its partial pressure divided by the total pressure, so

y_{B} = \frac{6}{60} = 0.1 = 1 \times 1 0^{- 1}

The value of

x

is 1.

JEE Main · 2021 · 20 Jul 2021 · Shift 2 · Integer answer

Practise more: all JEE Main PYQs on Solutions →

More JEE Main questions on Solutions

Elements P and Q form two types of non-volatile, non-ionizable compounds PQ and $PQ_{2}$ . When 1 g of PQ is dissolved in 50 g of solvent 'A', $Δ T_{b}$ was 1.176 K while when 1 g of $PQ_{2}$ is dissolved in 50 g of solvent 'A', …
JEE Main 2026View solution →
Consider a solution of $CO_{2} (g)$ dissolved in water in a closed container.

Which one of the following plots correctly represents variation of log (partial pressure of CO2 in vapour phase above water) [y-axis] with log (mole fraction of $CO_{2}$ …
JEE Main 2026View solution →
Given below are two statements:

Statement I: The Henry's law constant $K_{H}$ is constant with respect to variations in solution's concentration over the range for which the solutions is ideally dilute.
Statement II : $K_{H}$ does not diff …
JEE Main 2026View solution →
The osmotic pressure of a living cell is 12 atm at 300 K. The strength of sodium chloride solution that is isotonic with the living cell at this temperature is $____$ $g L^{- 1}$ . (Nearest integer)

Given: …
JEE Main 2026View solution →
A substance 'X' (1.5 g) dissolved in 150 g of a solvent 'Y' (molar mass $= 300 g mol^{- 1}$ ) led to an elevation of the boiling point by 0.5 K. The relative lowering in the vapour pressure of the solvent 'Y' is $____$ $\times 1 0^{- 2}$ . (Nearest integer)
[Giv …
JEE Main 2026View solution →
Which one of the following graphs accurately represents the plot of partial pressure of $CS_{2}$ vs its mole fraction in a mixture of acetone and $CS_{2}$ at constant temperature ?
JEE Main 2026View solution →