JEE Advanced 2023 · Paper 2 · Chemistry Q2

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ChemistrySingle correct+3 / -1Question 36 of 51

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

(I) and (II)

(II) and (III)

(III) and (IV)

(II) and (IV)

Answer and worked solution

Official answer: A

(I) True. Lyophobic sols, such as metal sols and sulphides, need special methods (dispersion or condensation). They do not form on simple mixing.

(II) True. An emulsion is a liquid dispersed in a liquid.

(III) False. Micelles form only above the critical micelle concentration and above the Kraft temperature, and only in suitable solvents.

(IV) False. The Tyndall effect needs the dispersed phase and the medium to differ in refractive index.

The correct set is (I) and (II).

Topics:Colloids Emulsions

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JEE Advanced 2023 · Paper 2, Chemistry question 2