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MCQEasyJEE 2025Colligative Properties

JEE Chemistry 2025 Question with Solution

XYXY is the membrane / partition between two chambers 11 and 22 containing sugar solutions of concentration c1c_{1} and c2c_{2} (c1>c2)\left(c_{1}>c_{2}\right) mol L−1\mathrm{mol} \, \mathrm{L}^{-1}. For the reverse osmosis to take place identify the correct condition

(Here p1p_{1} and p2p_{2} are pressures applied on chamber 11 and 22 )

Two adjacent chambers labeled 1 and 2 are separated by vertical membrane XY, with solution c1 on left and solution c2 on right.
  • A

    Membrane/Partition ; Cellophane, p1>πp_{1}>\pi

  • B

    Membrane/Partition ; Porous. p2>πp_{2}>\pi

  • C

    Membrane/Partition ; Parchment paper, p1>πp_{1}>\pi

  • D

    Membrane/Partition : Cellophane, p2>πp_{2}>\pi Choose the correct answer from the options given below: (1)\left(1\right) B and D only (2)\left(2\right) A and D only (3)\left(3\right) A and C only (4)\left(4\right) C only

Answer

Correct answer:C

Step-by-step solution

Standard Method

Given: Chamber 11 contains sugar solution of concentration c1c_1 and chamber 22 contains sugar solution of concentration c2c_2 with c1>c2c_1>c_2. The membrane XYXY separates the two chambers.

Find: The correct condition for reverse osmosis.

Reverse osmosis requires solvent to move from the region of higher solute concentration to the region of lower solute concentration by applying an external pressure greater than the osmotic pressure on the more concentrated side.

The osmotic pressure is given by

π=iCRT\pi = iCRT

Explanation from the solution

Since c1>c2c_1>c_2, chamber 11 is the more concentrated side. Therefore, for reverse osmosis, the applied pressure on chamber 11 must satisfy

p1>πp_1 > \pi

Also, the membrane must be semipermeable. From the given statements in the options, the solution identifies Parchment paper with p1>πp_1>\pi as the correct condition.

Therefore, the correct option is C.

Common mistakes

  • Applying pressure on the dilute side and taking p2>πp_2>\pi. This is wrong because reverse osmosis requires pressure to be applied on the more concentrated solution side. Use p1>πp_1>\pi since c1>c2c_1>c_2.

  • Choosing a porous membrane. This is wrong because reverse osmosis needs a semipermeable membrane, not an ordinary porous partition. Use an appropriate semipermeable membrane such as parchment paper or cellophane.

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