Ethane reacts with chlorine to make chloroethane and hydrogen chloride.
H3C−CH3+Cl−Cl→H3C−CH2−Cl+H−Cl \mathrm{H_3C-CH_3 + Cl-Cl \rightarrow H_3C-CH_2-Cl + H-Cl} H3C−CH3+Cl−Cl→H3C−CH2−Cl+H−Cl| Bond | C−H\mathrm{C-H}C−H | Cl−Cl\mathrm{Cl-Cl}Cl−Cl | C−Cl\mathrm{C-Cl}C−Cl | H−Cl\mathrm{H-Cl}H−Cl |
|---|---|---|---|---|
| Bond energy (kJ/mol\mathrm{kJ/mol}kJ/mol) | 413 | 243 | 338 | 432 |
Calculate the energy change for the reaction.
A different reaction has an energy change of -75 kJ/mol. Which reaction releases more energy per mole, the reaction above or the different reaction? Explain your answer.
106 exam-style questions on OCR GCSE Chemistry 3.2 Energetics, covering 3.2.1 Exothermic and endothermic reactions and reaction profiles and 3.2.2 Calculating energy change from bond energies. Each one has a worked solution and a mark scheme showing where the marks go.