An aqueous equilibrium mixture containing chromate and dichromate ions is represented by the equation:
2CrO42−(aq) [yellow]+2H+(aq)⇌Cr2O72−(aq) [orange]+H2O(l) 2\text{CrO}_4^{2-}(\text{aq}) \text{ [yellow]} + 2\text{H}^+(\text{aq}) \rightleftharpoons \text{Cr}_2\text{O}_7^{2-}(\text{aq}) \text{ [orange]} + \text{H}_2\text{O}(\text{l}) 2CrO42−(aq) [yellow]+2H+(aq)⇌Cr2O72−(aq) [orange]+H2O(l)A student adds a few drops of concentrated sodium hydroxide, NaOH(aq)\text{NaOH}(\text{aq})NaOH(aq), to the orange mixture at equilibrium.
What is the observed colour change?
The mixture turns yellow.
The mixture becomes a deeper orange.
The mixture turns green.
The mixture becomes colourless.
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.