Heating blue hydrated copper(II) sulfate is a reversible reaction: CuSO4⋅5H2O⇌CuSO4+5H2O\mathrm{CuSO_{4}\cdot5H_{2}O \rightleftharpoons CuSO_{4} + 5H_{2}O}CuSO4⋅5H2O⇌CuSO4+5H2O
Heating 25.0 g of the blue solid until it has all turned white takes in 7.8 kJ of energy.
The student cools the white solid, splits it into two equal portions, and adds water to one portion until it is blue again. Ignore any energy lost to the surroundings.
Which describes this last step?
The temperature rises, and 3.9 kJ3.9\,\mathrm{kJ}3.9kJ of energy is given out
The temperature falls, and 3.9 kJ3.9\,\mathrm{kJ}3.9kJ of energy is taken in
The temperature rises, and 7.8 kJ7.8\,\mathrm{kJ}7.8kJ of energy is given out
The temperature falls, and 7.8 kJ7.8\,\mathrm{kJ}7.8kJ of energy is taken in
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.