Calcium carbonate breaks down when it is heated.
CaCO3(s)⇌CaO(s)+CO2(g) \mathrm{CaCO_{3}(s) \rightleftharpoons CaO(s) + CO_{2}(g)} CaCO3(s)⇌CaO(s)+CO2(g)A student heats calcium carbonate strongly in an open crucible. The reaction does not reach equilibrium.
Why does the reaction not reach equilibrium?
Calcium oxide is a solid, so the reverse reaction cannot happen.
Strong heating stops the forward reaction from happening.
The crucible acts as a catalyst for the forward reaction.
Carbon dioxide escapes, so the reverse reaction cannot happen.
124 exam-style questions on OCR GCSE Chemistry 5.3 Equilibria, covering 5.3.1 Reversible reactions and dynamic equilibrium and 5.3.2 Changing the position of equilibrium. Each one has a worked solution and a mark scheme showing where the marks go.