X Y is the membrane/partition between two chambers 1 and 2 containing sugar solutions of concentration c₁ and c₂(c₁>c₂) mol L⁻¹. For the reverse osmosis to take place identify the correct condition.
(Here p₁ and p₂ are pressures applied on chamber 1 and 2 ).
A. Membrane/Partition : Cellophane, p₁>π
B. Membrane/Partition : Porous, p₂>π
C. Membrane/Partition : Parchment paper, p₁>π
D. Membrane/Partition : Cellophane, p₂>π
Choose the correct answer from the option given below:

Solution

Chemistry ma’am · 3 steps

Reverse osmosis needs a semipermeable wall and extra pressure on the concentrated side, here chamber 1.

1. Normal direction. Since c₁ > c₂, solvent naturally flows from chamber 2 (dilute) into chamber 1 (concentrated). The pressure that just stops this flow is the osmotic pressure π. For sugar, which does not ionise, it equals (c₁ - c₂)RT.
2. Two conditions. To reverse the flow, push on the concentrated side with p₁ > π. The partition must also be semipermeable, letting solvent through but not sugar. Cellophane and parchment paper are semipermeable. A porous partition lets sugar pass as well, so no osmosis of any kind can happen.

   Statement	Membrane	Pressure applied on	Reverse osmosis?
   A	Cellophane, semipermeable	chamber 1, concentrated	Yes
   B	Porous, lets sugar through	chamber 2, dilute	No
   C	Parchment paper, semipermeable	chamber 1, concentrated	Yes
   D	Cellophane, semipermeable	chamber 2, dilute	No, this only speeds up normal osmosis

3. So. Only A and C meet both conditions, so the answer is (a).

The idea to keep. For reverse osmosis, check two things: a semipermeable membrane, and pressure greater than π on the more concentrated solution. Pressure on the dilute side only helps normal osmosis.

Answer from the NTA final answer key. Solution by PrepWiser.