What will happen when red blood cells (RBCs) are kept in more than 0.9% (mass/ volume) sodium chloride solution?
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → Cells will shrink
In osmosis, water passes through a semipermeable membrane from the more dilute to the more concentrated solution. The fluid inside blood cells is isotonic with 0.9% (mass/volume) NaCl, so a NaCl solution of more than 0.9% is more concentrated (hypertonic). Water therefore flows out of the cells into the solution and the cells shrink.
Why the other options are incorrect
Option (2) Cells will swell — Incorrect. Swelling happens in a hypotonic solution, with less than 0.9% NaCl.
Option (3) Cells would neither shrink nor swell. — Incorrect. This happens only in an isotonic solution, 0.9% NaCl.
Option (4) Water would flow into the cell. — Incorrect. Water moves towards the more concentrated solution; here that is the outside solution, so water flows out of the cell, not into it.
NCERT (2026-27 edition):
Osmosis and Osmotic Pressure – …
Note: The same/similar question has been asked in different years by NTA as per the details given below:
| 2026 | 2025 | 2024 | 2023 | 2022 |
|---|---|---|---|---|
| 22-05 S2 22-05 S1 | – | – | – | – |