🩺 NEET🧪 Chemistry

Surface Chemistry

5 NEET Chemistry previous year questions on Surface Chemistry — options free on every question; 1 include the answer & explanation free, the rest unlock with PYQ Pass.

Q1 FREE PREVIEW

Consider the following statements related to colloids.
(I) Lyophobic colloids are not formed by simple mixing of dispersed phase and dispersion medium.
(II) For emulsions, both the dispersed phase and the dispersion medium are liquid.
(III) Micelles are produced by dissolving a surfactant in any solvent at any temperature.
(IV) Tyndall effect can be observed from a colloidal solution with dispersed phase having the same refractive index as that of the dispersion medium.

The option with the correct set of statements is

[JEE Advanced 2023, Paper-2]

a

(I) and (II)

b

(II) and (III)

c

(III) and (IV)

d

(II) and (IV)

✓ Correct answer: a)

(I) and (II)

Explanation

(I) Because there is no contact between the dispersed phase and the dispersion medium in Lyophobic colloids, special procedures are needed for its preparation; simple mixing will not generate it.
(II) Emulsions are colloids which are liquid in liquid type.
(III) When surfactant is dissolved in a suitable solvent, micelles form only at temperatures higher than Kraft's temperature.
(IV) For the Tyndall effect to occur, there must be a significant difference in refractive index between the dispersed phase and the dispersion medium.

Hence, (I) & (II) are correct statements.

Q2

Lyophilic sols are more stable than lyophobic sols because

[JEE Main 2021, 27 Aug (Shift 2)]

a

The colloidal particles have positive charge.

b

The colloidal particles have no charge.

c

The colloidal particles are solvated.

d

There are strong electrostatic repulsion between the negatively charged colloidal particles.

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Q3

Which of the following method is used for coagulation of the sol?

a

By mixing two oppositely charged sols.

b

By electrophoresis.

c

By addition of electrolytes.

d

All of the above.

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Q4

Pumice stone is an example of

[NEET 2023]

a

gel

b

solid sol

c

foam

d

sol

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Q5

Amongst the following statements regarding adsorption, those that are valid are

(a) \( \Delta \mathrm{H} \) becomes less negative as adsorption proceeds

(b) On a given adsorbent, ammonia is adsorbed more than nitrogen gas

(c) On adsorption, the residual force acting along the surface of the adsorbent increases

(d) With increase in temperature, the equilibrium concentration of adsorbate increases

[JEE Main 2020, 2 Sep (Shift 2)]

a

(c) and (d)

b

(a), and (b)

c

(d) and (a)

d

(b) and (c)

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