Colourless ions, L+\mathrm{L^{+}}L+ and M−\mathrm{M^{-}}M−, react reversibly to form the violet dissolved species LM\mathrm{LM}LM.
L+(aq)+M−(aq)⇌LM(aq) \mathrm{L^{+}(aq) + M^{-}(aq) \rightleftharpoons LM(aq)} L+(aq)+M−(aq)⇌LM(aq)A sealed flask contains a pale violet mixture at dynamic equilibrium. A student injects a small volume of concentrated, colourless solution containing M−\mathrm{M^{-}}M− ions and reseals the flask.
Predict how the colour of the mixture changes and explain why this happens.
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.