Hydrogen reacts with fluorine to form hydrogen fluoride.
H2+F2→2HF \mathrm{H_{2} + F_{2} \rightarrow 2HF} H2+F2→2HFA hydrogen molecule contains one H−H\mathrm{H{-}H}H−H bond, a fluorine molecule contains one F−F\mathrm{F{-}F}F−F bond and a hydrogen fluoride molecule contains one H−F\mathrm{H{-}F}H−F bond.
| Bond | H−H\mathrm{H{-}H}H−H | F−F\mathrm{F{-}F}F−F |
|---|---|---|
| Bond energy (kJ/mol\mathrm{kJ/mol}kJ/mol) | 436 | 158 |
The energy change for the reaction is -540 kJ/mol.
Calculate the bond energy of the H−F\mathrm{H{-}F}H−F bond.
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.