In a hot car engine, some of the nitrogen and oxygen from the air react to form nitrogen monoxide, NO.
N2(g)+O2(g)→2NO(g)\mathrm{N_{2}(g)} + \mathrm{O_{2}(g)} \rightarrow \mathrm{2NO(g)}N2(g)+O2(g)→2NO(g)
The table shows some bond energies.
| Bond | Bond energy / kJ mol−1\mathrm{kJ\,mol^{-1}}kJmol−1 |
|---|---|
| N≡N | 945 |
| O=O | 498 |
| N=O (in NO) | 630 |
Calculate the energy change for the reaction.
Nitrogen and oxygen are both present in the air around us, but they do not react at room temperature. Explain why nitrogen monoxide forms in a car engine but not in the air at room temperature. Use ideas about bond breaking, bond making, activation energy and the reaction profile in your answer.
Nitrogen monoxide reacts with more oxygen in the air to form nitrogen dioxide. State one environmental problem caused by oxides of nitrogen.
53 exam-style questions on Edexcel GCSE Chemistry 8.2 Heat energy changes in chemical reactions, covering 8.2.1 Exothermic and endothermic changes, 8.2.2 Bond breaking, bond making and overall energy change, 8.2.3 Calculating energy change from bond energies, and 8.2.4 Activation energy and reaction profiles. Each one has a worked solution and a mark scheme showing where the marks go.