Chemical energetics

Learning objectives

Define the standard enthalpy changes of reaction, formation, combustion and neutralisation at 298 K and 101 kPa, and use the sign of ΔH to classify a change as exothermic or endothermic

Draw and interpret energy profile (reaction pathway) diagrams, labelling ΔH and the activation energy Ea for exothermic and endothermic reactions

Calculate enthalpy changes from calorimetry results using q = mcΔT and ΔH = −mcΔT/n, and evaluate sources of error such as heat loss

Calculate ΔH from bond energies and explain why the answer differs from a data-book value when some of the bond energies used are averages

Apply Hess's law to build energy cycles from formation, combustion or bond energy data, including finding enthalpy changes that cannot be measured directly