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Purity and separating mixtures

Purity and separating mixtures

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Question 14

A student is given a crude sample of copper(II) sulfate pentahydrate, CuSO4⋅5H2O\text{CuSO}_4\cdot5\text{H}_2\text{O}CuSO4​⋅5H2​O, which is contaminated with insoluble silicon dioxide (SiO2\text{SiO}_2SiO2​) and a small amount of highly soluble impurities.

The student is asked to obtain pure, dry crystals of copper(II) sulfate pentahydrate using recrystallization and filtration techniques.

They write down the following steps for the procedure, which are not listed in the correct order:

  1. Filter the cold mixture under reduced pressure using a Büchner funnel to isolate the crystals.
  2. Dissolve the crude solid in the minimum volume of hot distilled water.
  3. Wash the obtained crystals with a small volume of ice-cold distilled water and dry them.
  4. Cool the hot filtrate slowly to room temperature, then place it in an ice bath to allow crystallization.
  5. Perform a hot gravity filtration of the mixture to remove the insoluble silicon dioxide.

What is the correct order of these steps to obtain the maximum yield of pure, dry crystals?

A

2, 5, 4, 1, 3

B

2, 4, 5, 1, 3

C

5, 2, 4, 1, 3

D

2, 5, 1, 4, 3

Markscheme

Purity and separating mixtures Questions

  1. GCSE
  2. /Chemistry
  3. /Purity and separating mixtures

46 exam-style questions on OCR GCSE Chemistry Purity and separating mixtures. Each one has a worked solution and a mark scheme showing where the marks go.

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