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Acids, bases and salt preparations

Acids, bases and salt preparations

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Question 7

Crystals of magnesium sulfate, MgSO4\text{MgSO}_4MgSO4​, can be prepared by reacting solid magnesium oxide, MgO\text{MgO}MgO, with dilute sulfuric acid.

a.

Write a chemical equation for this reaction.

[1]
b.

A student is given a sample of magnesium oxide containing small amounts of insoluble impurities. The steps below describe the method used to prepare some pure, dry crystals of magnesium sulfate from this sample:

  • Stage 1: Place 50 cm350\text{ cm}^350 cm3 of dilute sulfuric acid into a beaker and warm.
  • Stage 2: Add the impure magnesium oxide a little at a time and stir, until it is in excess.
  • Stage 3: Filter the mixture.
  • Stage 4: Heat the filtrate until the crystallisation point is reached.
  • Stage 5: Allow the filtrate to cool.
  • Stage 6: Filter off the crystals and dry with filter paper.

Why is the acid warmed in Stage 1?

[1]
c.

How will the student know when the magnesium oxide is in excess in Stage 2?

[1]
d.

How will the student know when the crystallisation point is reached in Stage 4?

[1]
e.

In which stage are the insoluble impurities removed?

[1]
Markscheme

Acids, bases and salt preparations Questions

  1. IGCSE
  2. /Chemistry
  3. /Acids, bases and salt preparations

23 exam-style questions on Edexcel IGCSE Chemistry Acids, bases and salt preparations. Each one has a worked solution and a mark scheme showing where the marks go.

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