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: When pressure larger than the osmotic pressure is applied on the solution side, reverse osmosis takes place.

Reason: Reverse osmosis may be used for desalination of sea water.

(a)

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. Reverse osmosis is used in desalination of sea water.