Hydrogen sulfide burns in oxygen to form sulfur dioxide and water.
2H2S+3O2→2SO2+2H2O \mathrm{2H_{2}S + 3O_{2} \rightarrow 2SO_{2} + 2H_{2}O} 2H2S+3O2→2SO2+2H2OThe table shows the bonds in one molecule of each substance.
| Molecule | Bonds in one molecule |
|---|---|
| H2S\mathrm{H_{2}S}H2S | two H−S\mathrm{H{-}S}H−S bonds |
| O2\mathrm{O_{2}}O2 | one O=O\mathrm{O=O}O=O bond |
| SO2\mathrm{SO_{2}}SO2 | two S=O\mathrm{S=O}S=O bonds |
| H2O\mathrm{H_{2}O}H2O | two O−H\mathrm{O{-}H}O−H bonds |
| Bond | H−S\mathrm{H{-}S}H−S | O=O\mathrm{O=O}O=O | S=O\mathrm{S=O}S=O | O−H\mathrm{O{-}H}O−H |
|---|---|---|---|---|
| Bond energy (kJ/mol\mathrm{kJ/mol}kJ/mol) | 347 | 498 | 523 | 463 |
What is the energy change for the reaction?
−780 kJ/mol-780\,\mathrm{kJ/mol}−780kJ/mol
−1062 kJ/mol-1062\,\mathrm{kJ/mol}−1062kJ/mol
+1062 kJ/mol+1062\,\mathrm{kJ/mol}+1062kJ/mol
−531 kJ/mol-531\,\mathrm{kJ/mol}−531kJ/mol
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.