Reversible Reactions and Equilibria
5 marks · EasyThis question is about reversibility in chemical reactions, especially in sealed containers.
What is meant by a reversible reaction? State the symbol used to represent a reversible reaction in a chemical equation.
Copper(II) sulfate crystals can lose water when heated and regain it when water is added.
Write a balanced chemical equation using symbols to show the reversible change involving hydrated and anhydrous copper(II) sulfate.
What does it mean if this reaction occurs in a sealed container?
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
Show answer
(a) — · must show A reversible reaction can go both forwards and backwards, Use of the double arrow symbol: or
(b(i)) CuSO4·5H2O(s) \rightleftharpoons CuSO4(s) + 5H2O(l) · must show Balanced reversible equation with correct symbols and state symbols
(b(ii)) — · must show No substances can enter or leave the container, Only heat can be exchanged
Show mark scheme and worked solution
Marking points
B1 (a) · 1 mark · States a reversible reaction can go both forwards and backwards
B2 (a) · 1 mark · Gives the correct reversible arrow (e.g., , )
B3 (b(i)) · 1 mark · Balanced reversible equation with correct state symbols for hydrated/anhydrous copper(II) sulfate
B4 (b(ii)) · 1 mark · States that in a sealed container no substances can enter or leave
B5 (b(ii)) · 1 mark · Mentions heat can be exchanged, but nothing else enters or leaves
Worked solution
a) A reversible reaction is a reaction where the products can react to reform the reactants, i.e., the reaction can go both forwards and backwards. It is represented in a chemical equation by the reversible arrow symbol: .
b(ii) In a sealed container, no substances are allowed to enter or leave the system during the reaction. Only energy (heat) can be transferred in or out, but the reactants and products remain inside.