Osmosis and Osmotic pressure play a significant role in biological processes. Osmotic pressure is a colligative property and depends on the concentration of solute and not on its nature. The osmotic pressure of human blood is 8.21 atm at 27 ⁰C. It is interesting to note that a 0.91% (mass/volume) solution of sodium chloride known as saline water is isotonic with fluids inside the human red blood cells. In this solution, the corpuscles neither swell nor shrink. Therefore, medicines are mixed with saline water before being injected into the veins.

In the following question, a statement of assertion followed by a statement of reason is given. Choose the correct answer out of the following choices:

(a) Assertion and reason both are correct statements and reason is the correct explanation for assertion.

(b) Assertion and reason both are correct statements and reason is not the correct explanation for assertion.

(c) Assertion is a correct statement but reason is a wrong statement.

(d) Assertion is a wrong statement but reason is a correct statement.

Assertion: On placing RBC's in 0.5% NaCl solution, they will shrink due to plasmolysis.

Reason: RBC's are isotonic with 0.91% NaCl solution.

(d)

If the salt concentration is less than 0.9% (mass/volume), the solution is said to be hypotonic. In this case, water will flow into the cells if placed in this solution and they would swell.