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3.2 Methods of separating and purifying substances

3.2 Methods of separating and purifying substances

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Question 23

During the purification of an impure sample of a solid organic product via recrystallisation, a student performs the following sequence of steps:

  1. Dissolve the impure solid in the minimum volume of hot solvent.
  2. Filter the hot solution through fluted filter paper under gravity.
  3. Cool the filtrate slowly to room temperature, then place it in an ice bath.
  4. Filter the cold mixture under reduced pressure using a Büchner funnel.
  5. Wash the collected crystals.
  6. Dry the purified crystals in a desiccator.

Which of the following correctly identifies both the primary purpose of Step 2 and the correct choice of wash liquid for Step 5?

A

Step 2: To remove insoluble impurities; Step 5: Wash with a minimum volume of ice-cold solvent.

B

Step 2: To remove soluble impurities; Step 5: Wash with a large volume of ice-cold solvent.

C

Step 2: To remove insoluble impurities; Step 5: Wash with a minimum volume of hot solvent.

D

Step 2: To remove soluble impurities; Step 5: Wash with a large volume of hot solvent.

Markscheme

3.2 Methods of separating and purifying substances Questions

  1. GCSE
  2. /Chemistry
  3. /3.2 Methods of separating and purifying substances

107 exam-style questions on Edexcel GCSE Chemistry 3.2 Methods of separating and purifying substances, covering 3.2.1 Pure substances and mixtures, 3.2.2 Techniques for separating mixtures, 3.2.3 Paper chromatography and Rf values, and 3.2.4 Making water potable. Each one has a worked solution and a mark scheme showing where the marks go.

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