JEE Main 2021 · 25 July · evening · Single correct · +4 / −1
Match List I with List II :
Choose the most appropriate answer from the options given below
| List-I Example of colloids | List - II Classification |
|---|---|
| (a) Cheese | (i) dispersion of liquid in liquid |
| (b) Pumice stone | (ii) dispersion of liquid in gas |
| (c) Hair cream | (iii) dispersion of gas in solid |
| (d) Cloud | (iv) dispersion of liquid in solid |
- (a) (a)-(iv), (b)-(iii), (c)-(ii), (d)-(i)
- (b) (a)-(iv), (b)-(i), (c)-(iii), (d)-(ii)
- (c) (a)-(iii), (b)-(iv), (c)-(i), (d)-(ii)
- (d) (a)-(iv), (b)-(iii), (c)-(i), (d)-(ii)
Answer and solution
Answer (d) (a)-(iv), (b)-(iii), (c)-(i), (d)-(ii)
Solution
Chemistry ma’am · 3 steps
For every colloid, ask two things: what is spread out, and what is it spread through?
- Name both phases. A colloid is classified by its dispersed phase (the tiny particles) and its dispersion medium (the continuous part around them). List II always reads as "dispersed phase in medium".
Example Dispersed phase Dispersion medium Matches Cheese (gel) liquid solid (iv) liquid in solid Pumice stone (solid foam) gas (trapped air pockets) solid (iii) gas in solid Hair cream (emulsion) liquid (oil) liquid (water) (i) liquid in liquid Cloud (aerosol) liquid (water droplets) gas (air) (ii) liquid in gas - Deciding pair. Options (a) and (d) agree on cheese and pumice stone. They differ only on hair cream and cloud. Hair cream is an emulsion of oil and water, and a cloud is water droplets floating in air.
- So. The correct matching is cheese with (iv), pumice stone with (iii), hair cream with (i) and cloud with (ii), which is option (d).
The idea to keep. Name the colloid type first: gel is liquid in solid, solid foam is gas in solid, emulsion is liquid in liquid, aerosol is liquid or solid in gas. The medium is always the continuous part.
Answer from the NTA final answer key. Solution by PrepWiser.