Energetics — A/L Chemistry

Chemical energetics studies enthalpy changes (ΔH), Hess's law cycles, lattice energy (Born-Haber cycles), entropy (ΔS), and Gibbs free energy (ΔG) determining reaction spontaneity.

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1. Hess's Law & Enthalpy Cycles: Constructing accurate thermochemical cycles to calculate enthalpy of reaction from enthalpies of formation (ΔH = ΣΔH_f(products) - ΣΔH_f(reactants)) or combustion.
2. Born-Haber Cycles: Stepwise evaluation of lattice enthalpy accounting for atomization, ionization energy, electron affinity, and bond dissociation enthalpy with correct signs.
3. Spontaneity Equation (ΔG = ΔH - TΔS): Determining temperature thresholds where endothermic or entropy-decreasing processes become spontaneous (ΔG < 0).