Chemical Energetics: Thermochemistry structured questions · GCE A-Level H1 Chemistry

Learning objectives

• explain that most chemical reactions are accompanied by energy changes, principally in the form of heat usually associated with the breaking and forming of chemical bonds; the reaction can be exothermic (∆H negative) or endothermic (∆H positive)
• construct and interpret an energy profile diagram, in terms of the enthalpy change of the reaction and of the activation energy (see also Section 7)
• explain and use the terms: — enthalpy change of reaction and standard conditions, with particular reference to: formation; combustion; neutralisation
• explain and use the terms: — bond energy (∆H positive, i.e. bond breaking) (see also Section 2)
• explain and use the terms: — lattice energy (∆H negative, i.e. gaseous ions to solid lattice)
• calculate enthalpy changes from appropriate experimental results, including the use of the relationship: heat change = mc∆T
• explain, in qualitative terms, the effect of ionic charge and of ionic radius on the numerical magnitude of a lattice energy
• apply Hess’ Law to carry out calculations involving given simple energy cycles and relevant energy terms (restricted to enthalpy changes of formation, combustion and neutralisation), with particular reference to: — determining enthalpy changes that cannot be found by direct experiment, e.g. an enthalpy change of formation from enthalpy changes of combustion
• apply Hess’ Law to carry out calculations involving given simple energy cycles and relevant energy terms (restricted to enthalpy changes of formation, combustion and neutralisation), with particular reference to: — average bond energies [construction of energy cycles is not required]