Nitrogen dioxide, NO2(g), is formed when nitrogen monoxide, NO(g), undergoes oxidation as shown. 2 \mathrm{NO}(\mathrm{g})+\mathrm{O}_{2}(\mathrm{~g}) \rightleftharpoons 2 \mathrm{NO}_{2}(\mathrm{~g}) \quad \Delta \mathrm{H}=-62 \mathrm{~kJ} \mathrm{~mol}^{-1} A change was imposed on an equilibrium

mixture of NO2, NO and O2. The mixture returned to equilibrium and another change was imposed.The following graph shows the effects of the two changes. Identify the changes that best account for the shape of the graph.