(HT only) Distinguish bond energy calculations from reaction profile interpretation.

In the subtopic The energy change of reactions (HT only), this learning objective focuses on (HT only) Distinguish bond energy calculations from reaction profile interpretation. It belongs to Exothermic and endothermic reactions in AQA GCSE Chemistry 8462 Unit 4.5 Energy changes, so the explanation must stay inside energy-transfer, reaction-profile, cell, fuel-cell, exothermic, endothermic, activation-energy or bond-energy context as appropriate. Approved keywords to use include HT only, calculation, bond energy. Reaction profile interpretation. means a qualitative analysis of a plotted energy diagram that identifies whether a reaction is exothermic or endothermic by comparing the relative energies of reactants, products, and the activation energy Avoid the mistake of students think that the shape of a reaction profile can be used to calculate the exact energy change of a reaction, or that the activation energy shown on the profile is the same as the bond energies used in calculations; instead, explain that a reaction profile is a qualitative diagram showing the relative energies of reactants, transition state and products, and that it cannot provide numerical bond‑energy values. Bond‑energy calculations use tabulated average energies for specific bonds to determine the overall energy change, while a reaction profile only indicates whether a reaction is exothermic or endothermic and the relative size of the activation energy For exam answers, when you calculate a reaction’s ΔE using bond energies, first sketch the reaction profile: draw reactants, products, activation energy and overall ΔE. Then, after you finish the bond‑energy calculation, check that the sign of ΔE matches the profile’s overall energy change (negative for exothermic, positive for endothermic)