Arrange the following steps in the correct sequence to carry out reverse osmosis
(A) Two solutions having different concentrations of the same solute are taken.
(B) Very high external pressure is applied on the high concentration side.
(C) A semipermeable membrane is inserted between the two solutions.
(D) Solvent flows from the high concentration side to the low concentration one.
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → (A), (C), (B), (D)
In osmosis the solvent flows through a semipermeable membrane from the dilute solution into the concentrated one. If a pressure larger than the osmotic pressure is applied on the concentrated side, the flow is reversed and the solvent is pushed out of the concentrated solution. This is reverse osmosis, used in the desalination of sea water.
The steps in order:
(A) Two solutions of different concentration of the same solute are taken.
(C) A semipermeable membrane is placed between them; without it there is no osmosis to reverse.
(B) A very high external pressure is applied on the high concentration side.
(D) The solvent now flows from the high concentration side to the low concentration side.
Shortcut: Taking the solutions (A) comes first and the solvent flow (D) last, which leaves Options (1) and (2). The membrane must be in place before pressure is applied, so (C) comes before (B): Option (2).
NCERT (2026-27 edition):
Reverse Osmosis and Water Purification – “The direction of osmosis can be reversed if a pressure larger than the osmotic pressure is applied to the solution side. That is, now the pure solvent flows out of the solution through the semi permeable membrane. This phenomenon is called reverse osmosis and is of great practical utility.”