At the very high temperatures inside car engines, nitrogen reacts with oxygen to form nitrogen monoxide. $\tfrac{1}{2}\text{N}_2(g) + \tfrac{1}{2}\text{O}_2(g) \rightarrow \text{NO}(g) \qquad \Delta H^{\circ} = +90\,\text{kJ mol}^{-1}$ The reaction has activation energy $E_a$. Which reaction profile diagram shows this reaction correctly?
Chemistry 9701 · AS & A Level · Chemical energetics