A student heats some blue hydrated copper sulfate crystals in a boiling tube. The crystals turn white and water vapour is given off. When the white solid has cooled, the student adds a few drops of water to it. The solid turns blue again and the boiling tube becomes warm.
hydrated copper sulfate ⇌ \rightleftharpoons\,⇌ anhydrous copper sulfate + water
State what the symbol ⇌ \rightleftharpoons\,⇌ shows about this reaction.
Give the colour change seen when water is added to anhydrous copper sulfate.
State the condition the student changed to make the forward reaction happen.
The boiling tube becomes warm when water is added to the anhydrous copper sulfate.
Give the name of the type of reaction that gives out heat energy.
State whether the forward reaction, when the blue crystals are heated, is exothermic or endothermic.
Anhydrous copper sulfate is used to test for water. Suggest why this test cannot show that a sample of water is pure.
45 exam-style questions on Edexcel GCSE Chemistry 5.2 Reversible reactions and equilibria, covering 5.2.1 Reversible reactions and dynamic equilibrium, 5.2.2 The Haber process, and 5.2.3 Changing the position of a dynamic equilibrium. Each one has a worked solution and a mark scheme showing where the marks go.