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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 17

A student is provided with a solid mixture containing three substances:

  • Cobalt(II) carbonate, CoCO3\text{CoCO}_3CoCO3​ (insoluble in both hot and cold water)
  • Benzoic acid, C6H5COOH\text{C}_6\text{H}_5\text{COOH}C6​H5​COOH (soluble in hot water, but sparingly soluble in cold water)
  • Sodium chloride, NaCl\text{NaCl}NaCl (highly soluble in both hot and cold water)

The student wants to obtain a pure, dry sample of cobalt(II) carbonate (CoCO3\text{CoCO}_3CoCO3​) from this mixture. Which of the following experimental procedures should the student use?

A

Add cold water to the mixture, filter, wash the residue with cold water, and dry.

B

Add hot water to the mixture, filter while hot, wash the residue with hot water, and dry.

C

Add hot water to the mixture, filter while hot, cool the filtrate to crystallise, and filter to collect the crystals.

D

Add hot water to the mixture, cool the mixture to room temperature, filter, wash the residue with cold water, and dry.

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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