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MCQEasyJEE 2024Purification Methods (Crystallisation, Sublimation, Distillation)

JEE Chemistry 2024 Question with Solution

The technique used for purification of steam volatile water immiscible substance is:

  • A

    Fractional distillation

  • B

    Fractional distillation under reduced pressure

  • C

    Distillation

  • D

    Steam distillation

Answer

Correct answer:D

Step-by-step solution

Standard Method

Given: A purification technique is required for a substance that is steam volatile and water immiscible.

Find: The correct technique among the given options.

Steam distillation is specifically used for substances that are volatile in steam and immiscible with water. In this method, steam is passed through the mixture, and the volatile compound vaporizes along with steam at a temperature lower than its normal boiling point.

Fractional distillation is used mainly for separating miscible liquids with different boiling points. Fractional distillation under reduced pressure is useful for heat-sensitive substances, but it is not the characteristic method identified by steam volatility and water immiscibility. Ordinary distillation is too general and does not specifically use steam.

Therefore, the correct option is D, Steam distillation.

Direct Concept Check

Given: The substance is steam volatile and water immiscible.

Find: The matching purification method.

Whenever a question mentions both steam volatile and immiscible in water, the direct technique is steam distillation.

Therefore, the correct option is D.

Common mistakes

  • Choosing fractional distillation because it is a common separation method. This is incorrect because fractional distillation is mainly for miscible liquids with close boiling points. Use steam distillation when the substance is steam volatile and immiscible with water.

  • Confusing reduced pressure distillation with steam distillation. Reduced pressure distillation lowers the boiling point by decreasing pressure, but it is not the defining method for water-immiscible steam volatile substances. Focus on the keywords in the question.

  • Selecting ordinary distillation because the substance is volatile. This is incomplete reasoning because the question specifically mentions steam volatile and water immiscible. The correct specialized method is steam distillation.

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