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Solutions · Question 18

JEE Main 2026 (Online) 23rd January Evening ShiftNumericalEasy📈 Topic in 16% papers+4
1

Two liquids A and B form an ideal solution. At 320 K, the vapour pressure of the solution, containing 3 mol of A and 1 mol of B is 500 mm Hg. At the same temperature, if 1 mol of A is further added to this solution, vapour pressure of the solution increases by 20 mm Hg. Vapour pressure (in mm Hg) of B in pure state is . (Nearest integer)

Answer

200

Solution

Raoult's law: p = xA p A + xB p B

Solution 1 (xA = 34, xB = 14): 34 p A + 14 p B = 500

3p A + p B = 2000 ...(i)

Solution 2 (xA = 45, xB = 15): 45 p A + 15 p B = 520

4p A + p B = 2600 ...(ii)

(ii) − (i): p A = 600 mm Hg

p B = 2000 - 3(600) = 200 mm Hg

Answer: 200

JEE Main 2026 (Online) 23rd January Evening Shift

Keep practising — Solutions

2

Consider a solution of CO2(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 CO2 in water) [x-axis] at 25 ?

  1. [figure]
  2. [figure]
  3. [figure]
  4. [figure]
JEE Main 2026 (Online) 22nd January Morning Shift
3

Given below are two statements : In the light of the above statements, choose the correct answer from the options given below

  1. Both Statement I and Statement II are true
  2. Statement I is true but Statement II is false
  3. Statement I is false but Statement II is true
  4. Both Statement I and Statement II are false
JEE Main 2026 (Online) 22nd January Morning Shift
4

Elements P and Q form two types of non-volatile, non-ionizable compounds PQ and PQ2. When 1 g of PQ is dissolved in 50 g of solvent 'A', Tb was 1.176 K while when 1 g of PQ2 is dissolved in 50 g of solvent 'A', Tb was 0.689 K. (Kb of 'A' = 5 K kg mol-1). The molar masses of elements P and Q (in g mol-1) respectively, are :

  1. 25, 60
  2. 60, 25
  3. 65, 145
  4. 70, 110
JEE Main 2026 (Online) 21st January Morning Shift
5

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 : R = 0.08 L atm K-1 mol-1 Assume complete dissociation of NaCl (Given: Molar mass of Na and Cl are 23 and 35.5 g mol-1 respectively.)

JEE Main 2026 (Online) 21st January Evening Shift
6

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 10-2. (nearest integer) [Given: Kb of the solvent = 5.0 K kg mol-1] Assume the solution to be dilute and no association or dissociation of X takes place in solution.

JEE Main 2026 (Online) 21st January Evening Shift
7

HA(aq) H+(aq) + A-(aq) The freezing point depression of a 0.1 m aqueous solution of a monobasic weak acid HA is 0.20 C. The dissociation constant for the acid is Given: Kf(H2O) = 1.8 K kg mol-1, molality ≡ molarity

  1. 1.90 10-3
  2. 1.38 10-3
  3. 1.1 10-2
  4. 1.89 10-1
JEE Main 2025 (Online) 8th April Evening Shift
8

Which of the following binary mixtures does not show the behaviour of minimum boiling azeotropes?

  1. CH3OH + CHCl3
  2. C6H5OH + C6H5NH2
  3. H2O + CH3COC2H5
  4. CS2 + CH3COCH3
JEE Main 2025 (Online) 8th April Evening Shift
9

The percentage dissociation of a salt (MX3) solution at given temperature (van't Hoff factor i = 2) is % (Nearest integer)

JEE Main 2025 (Online) 7th April Morning Shift
10

Liquid A and B form an ideal solution. The vapour pressures of pure liquids A and B are 350 and 750 mm Hg respectively at the same temperature. If xA and xB are the mole fraction of A and B in solution while yA and yB are the mole fraction of A and B in vapour phase, then,

  1. (xA - yA) < (xB - yB)
  2. xAxB = yAyB
  3. xAxB < yAyB
  4. xAxB > yAyB
JEE Main 2025 (Online) 7th April Evening Shift
11

Match List - I with List - II. Choose the correct answer from the options given below :

  1. A-III, B-I, C-IV, D-II
  2. A-III, B-IV, C-I, D-II
  3. A-II, B-I, C-IV, D-III
  4. A-II, B-IV, C-I, D-III
JEE Main 2025 (Online) 7th April Evening Shift

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