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.
Practise Edexcel GCSE Chemistry Reversible reactions and equilibria with exam-style questions for Foundation and Higher tier. 38 questions, matched to the Edexcel GCSE Chemistry (1CH0) specification and written in Paper 1 and Paper 2 style. Every question includes a full worked solution and mark scheme, so you can see where marks are awarded rather than just whether you got the answer right.
