The R(aq)\text{R}\text{(aq)}R(aq) particles are orange. The P(aq)\text{P}\text{(aq)}P(aq), Q(aq)\text{Q}\text{(aq)}Q(aq) and S(aq)\text{S}\text{(aq)}S(aq) particles are colourless.
A closed mixture has reached equilibrium.
P(aq)+Q(aq)⇌R(aq)+S(aq)\text{P}\text{(aq)} + \text{Q}\text{(aq)} \rightleftharpoons \text{R}\text{(aq)} + \text{S}\text{(aq)}P(aq)+Q(aq)⇌R(aq)+S(aq)
A small volume of concentrated S(aq)\text{S}\text{(aq)}S(aq) solution is added. The change in the total volume is negligible.
Which statement describes the mixture when it reaches a new equilibrium?
It is deeper orange, because adding S increases the amount of every product
It is paler orange, because the forward reaction stops
It is paler orange, because R and S react to form more P and Q
It is deeper orange, because P and Q react to use up the added S
109 exam-style questions on AQA GCSE Chemistry 6.2 Reversible reactions and dynamic equilibrium, covering 6.2.1 Reversible reactions, 6.2.2 Energy changes and reversible reactions, 6.2.3 Equilibrium, 6.2.4 The effect of changing conditions on equilibrium, 6.2.5 The effect of changing concentration, 6.2.6 The effect of temperature changes on equilibrium, and 6.2.7 The effect of pressure changes on equilibrium. Each one has a worked solution and a mark scheme showing where the marks go.