Calcium carbonate undergoes endothermic thermal decomposition in a kiln. Its reaction profile shows an activation energy of 210 kJ/mol. Four proposed values for the overall energy change are -175 kJ/mol, 0 kJ/mol, +175 kJ/mol and +260 kJ/mol.
Which statement could be correct for this reaction profile?
The overall energy change is +260 kJ/mol+260\,\mathrm{kJ/mol}+260kJ/mol.
The overall energy change is −175 kJ/mol-175\,\mathrm{kJ/mol}−175kJ/mol.
The overall energy change is 0 kJ/mol0\,\mathrm{kJ/mol}0kJ/mol.
The overall energy change is +175 kJ/mol+175\,\mathrm{kJ/mol}+175kJ/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.