Iron(III) ions (Fe3+\text{Fe}^{3+}Fe3+) react reversibly with thiocyanate ions (SCN−\text{SCN}^-SCN−) to form iron(III) thiocyanate complex ions ([Fe(SCN)]2+[\text{Fe(SCN)}]^{2+}[Fe(SCN)]2+).
Iron(III) ions in solution are pale yellow, thiocyanate ions are colourless, and [Fe(SCN)]2+[\text{Fe(SCN)}]^{2+}[Fe(SCN)]2+ ions are deep red.
Fe3+(aq)+SCN−(aq)⇌[Fe(SCN)]2+(aq) \text{Fe}^{3+}(\text{aq}) + \text{SCN}^-(\text{aq}) \rightleftharpoons [\text{Fe(SCN)}]^{2+}(\text{aq}) Fe3+(aq)+SCN−(aq)⇌[Fe(SCN)]2+(aq)The mixture is placed in a beaker and left until a state of dynamic equilibrium is reached.
The conditions of the system are then altered to favour the reverse reaction.
Explain what you would observe as the mixture reaches its new equilibrium.
38 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.