Core Practical: Preparing a Pure Dry Sample of a Soluble Salt

This lesson covers the Core Practical for preparing a pure, dry sample of a soluble salt as required by the Edexcel GCSE Combined Science specification (1SC0). This is a required practical that you must know in detail, including the method, the reasoning behind each step, and how to evaluate results.

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Aim

To prepare a pure, dry sample of a soluble salt (e.g. copper sulfate) by reacting an acid with an excess of an insoluble base or insoluble carbonate.

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Background

This practical uses the reaction between sulfuric acid and copper oxide to make copper sulfate crystals.

Equation

copper oxide + sulfuric acid → copper sulfate + water

CuO(s) + H₂SO₄(aq) → CuSO₄(aq) + H₂O(l)

Copper oxide is an insoluble base — it does not dissolve in water but does react with acid.

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Apparatus