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Surface Chemistry question

2023 · Shift 2 · Q2
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Surface Chemistry question

2023 · Shift 2 · Q2

JEE AdvancedChemistrySurface ChemistryMCQ+3 / −1
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 :
  1. A
    (I) and (II)
  2. B
    (II) and (III)
  3. C
    (III) and (IV)
  4. D
    (II) and (IV)
View written solutionFree

Correct answer: A

  1. Statement (I): Lyophobic colloids are not formed by simple mixing of dispersed phase and dispersion medium.
    This is true.
    Lyophobic sols have very little affinity between dispersed phase and dispersion medium, so they are generally prepared by special methods such as dispersion methods or condensation methods, not by simple mixing.

  2. Statement (II): For emulsions, both the dispersed phase and the dispersion medium are liquid.
    This is true.
    By definition, an emulsion is a colloidal system in which both phases are liquids, for example, oil in water or water in oil.

  3. Statement (III): Micelles are produced by dissolving a surfactant in any solvent at any temperature.
    This is false.
    Micelles form only:

    • above a certain concentration called the critical micelle concentration (CMC), and
    • above a certain temperature called the Krafft temperature.
      Also, they are not formed in any solvent.

  4. Statement (IV): Tyndall effect can be observed from a colloidal solution with dispersed phase having the same refractive index as that of the dispersion medium.
    This is false.
    Tyndall effect occurs due to scattering of light by colloidal particles. If the refractive index of dispersed phase and dispersion medium is the same, scattering is negligible, so Tyndall effect is not observed.

  5. Therefore, the correct statements are: (I) and (II)\text{(I) and (II)}(I) and (II)

  6. Hence, the correct option is: A\boxed{\text{A}}A​

  7. Comparison with stored answer:
    Stored correct answer = A
    Derived answer = A
    So, they agree.

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