JEE Main · 2008 · 27 Apr 2008 · Offline · Solutions

WhatsApp Email

8 0^{\circ} C

, the vapour pressure of pure liquid '

A

' is 520 mm Hg and that of pure liquid '

B

' is 1000 mm Hg . If a mixture solution of ' A ' and ' B ' boils at

8 0^{\circ} C

and 1 atm pressure, the amount of ' A ' in the mixture is (

1 atm = 760 mm Hg

)

(A)52 mol percent
(B)34 mol percent
(C)48 mol percent
(D)50 mol percent✓ Correct

Answer: (D)

Solution

For an ideal mixture the total vapour pressure is the sum of the partial pressures,

P = P_{A}^{\circ} X_{A} + P_{B}^{\circ} (1 - X_{A})

. At the boiling point this equals one atmosphere,

760 mm Hg

, so

760 = 520 X_{A} + 1000 (1 - X_{A})

. Expanding gives

760 = 1000 - 480 X_{A}

, hence

480 X_{A} = 240

and

X_{A} = 0.5

. The mixture is therefore

50

mole percent in

A

JEE Main · 2008 · 27 Apr 2008 · Offline · Single correct option

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 →