UPSC Prelims 2005 Q71: Science & Technology – Biology
Consider the following statements :
1. During the process of osmosis, the solvent travels from the concentrated solution to the dilute
solution.
2. In the reverse osmosis, external pressure is applied to the dilute solution.
Which of the statements given above is/are correct?
- (a) 1 only
- (b) 2 only
- (c) Both 1 and 2
- (d) Neither 1 nor 2
Answer: (d) Neither 1 nor 2
Explanation
Osmosis and reverse osmosis
| Statement | Verdict |
|---|---|
| 1. Solvent moves from concentrated to dilute solution | False: it moves from dilute to concentrated |
| 2. In reverse osmosis pressure is applied to the dilute solution | False: it is applied to the concentrated solution |
Neither statement is correct.
Answer: (d) Neither 1 nor 2.
Why each option is right or wrong
- (a) Incorrect. The direction of solvent flow is stated wrongly.
- (b) Incorrect. Pressure is applied to the concentrated side.
- (c) Incorrect. Both statements are wrong.
- (d) CORRECT. Both statements are false.
Key point
Osmosis: dilute to concentrated through semipermeable membrane; reverse osmosis: apply pressure beyond osmotic pressure on concentrated side.
Remember
In osmosis the solvent moves from dilute to concentrated solution.
Common mistakes
- Reversing the direction of osmosis.
- Applying pressure on the dilute side.
- Forgetting that RO is used for desalination.
Exam tip
RO needs pressure more than osmotic pressure on the concentrated solution.
Sources
- NCERT Class XII Chemistry — Solutions
- NCERT Class XI Biology — Transport in Plants (osmosis)