A sealed container holds an equilibrium mixture of phosphorus pentachloride, phosphorus trichloride and chlorine.
Phosphorus pentachloride and phosphorus trichloride are colourless. Chlorine is greenish-yellow.
PCl5(g)⇌PCl3(g)+Cl2(g)\text{PCl}_5\text{(g)} \rightleftharpoons \text{PCl}_3\text{(g)} + \text{Cl}_2\text{(g)}PCl5(g)⇌PCl3(g)+Cl2(g)
The pressure is decreased at constant temperature. The mixture is allowed to reach equilibrium again.
Which statement correctly predicts the appearance of the mixture?
The greenish-yellow colour is unchanged because the forward and reverse reactions have equal rates at equilibrium
The greenish-yellow colour becomes more intense because lower pressure favours the side with more gas molecules
The greenish-yellow colour becomes less intense because lower pressure favours the side with fewer gas molecules
The greenish-yellow colour is unchanged because each side contains the same number of chlorine atoms
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.