UPSC Prelims 2005 · General Studies
Question 71: Science and Technology
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?
AnswerThe answer is (d).
In osmosis the solvent moves through a semipermeable membrane from the dilute solution to the concentrated one, so statement 1 reverses it. In reverse osmosis, pressure higher than the osmotic pressure is applied to the concentrated solution, forcing solvent out to the dilute side; this is how seawater is desalinated. Statement 2 therefore also fails.
- 1. The solvent moves from the dilute to the concentrated solution.
- 2. In reverse osmosis pressure is applied to the concentrated solution.
How you could have got this
- If you were sure statement 1 is not correct, (a) and (c) go: each of them includes 1.
What you needed to know: The solvent moves from the dilute to the concentrated solution.
- Then, if you were sure statement 2 is not correct, (b) goes: it includes 2.
What you needed to know: In reverse osmosis pressure is applied to the concentrated solution.
Only (d) is left. This one needs every statement.
This follows an unofficial answer: UPSC has not published its key for this year, and if that answer is wrong, so is this path.
Which options go is worked out from UPSC’s key and the options, not by a model.
Why each option is right or wrong
- (a) Statement 1 reverses the direction of osmosis.
- (b) Statement 2 applies pressure on the wrong side.
- (c) Both statements are wrong.
- (d) Correct: neither statement is right.
Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2005, General Studies. UPSC's own paper isn't online; the words are from a published compilation. The paper on upsc.gov.in.