Dinitrogen tetroxide (N2O4\text{N}_2\text{O}_4N2O4) is a colourless gas.
Nitrogen dioxide (NO2\text{NO}_2NO2) is a brown gas.
These gases can exist together in dynamic equilibrium according to the equation:
N2O4(g)⇌2NO2(g)ΔH=+58 kJ/mol \text{N}_2\text{O}_4(\text{g}) \rightleftharpoons 2\text{NO}_2(\text{g}) \quad \Delta H = +58\text{ kJ/mol} N2O4(g)⇌2NO2(g)ΔH=+58 kJ/molA mixture of these gases is allowed to reach equilibrium in a sealed container of fixed volume at 20∘C20^\circ\text{C}20∘C. This equilibrium mixture is pale brown in colour.
The sealed container is heated to 90∘C90^\circ\text{C}90∘C.
As the temperature of the gas mixture increases, the pressure of the gas mixture also increases.
Predict the effect of the increase in temperature on the position of equilibrium.
Predict the effect of the increase in pressure on the position of equilibrium.
Suggest why it is difficult to predict which way the equilibrium will shift.
Suggest why the equilibrium mixture is a darker shade of brown at 90∘C90^\circ\text{C}90∘C than the equilibrium mixture at 20∘C20^\circ\text{C}20∘C.
28 exam-style questions on Edexcel IGCSE Chemistry Reversible reactions and equilibria. Each one has a worked solution and a mark scheme showing where the marks go.