Energetics covers thermodynamics — enthalpy, Hess\'s law, Born-Haber cycles, entropy, and free energy. Kinetics covers rates — collision theory, rate equations, orders, the Arrhenius equation, and catalysis.
Standard enthalpy changes: formation ΔHf°, combustion ΔHc°, neutralisation, atomisation, ionisation, electron affinity. Hess\'s law: ΔH for a reaction is the same regardless of route. Calculate ΔH using formation enthalpies: ΔH = ΣΔHf°(products) − ΣΔHf°(reactants). Or using combustion: ΔH = ΣΔHc°(reactants) − ΣΔHc°(products). Bond enthalpies: ΔH ≈ Σ(bonds broken) − Σ(bonds formed). Born-Haber cycle for ionic compounds: lattice enthalpy from Hess\'s law using atomisation, ionisation, electron affinity, formation. Entropy S: measure of disorder (J/K/mol). ΔS = ΣS°(products) − ΣS°(reactants). Gibbs free energy: ΔG = ΔH − TΔS. Reaction spontaneous when ΔG < 0.
Rate = change in concentration / time. Collision theory: rate depends on frequency of successful collisions (sufficient energy + correct orientation). Rate equation: rate = k[A]ᵐ[B]ⁿ (k = rate constant, m and n are orders). Orders determined experimentally (cannot be deduced from equation). Zero order: rate independent of [A]. First order: rate ∝ [A], half-life constant. Second order: rate ∝ [A]². Rate-concentration graphs. Initial rates method: compare experiments where one concentration changes. Arrhenius equation: k = Ae^(−Ea/RT). ln k = ln A − Ea/(RT). Plot ln k vs 1/T: gradient = −Ea/R. Catalysts: provide alternative route with lower Ea. Homogeneous (same phase) vs heterogeneous (different phase). Mechanisms: rate-determining step is the slowest; its molecularity determines the rate equation.
Orders cannot be deduced from the balanced equation — they must be determined experimentally. Method 1 (Initial rates): run multiple experiments changing one concentration at a time. Compare: if doubling [A] doubles rate → first order in A; if it quadruples rate → second order; if no change → zero order. Method 2 (Concentration-time graph): plot [A] vs time. If the half-life is constant (time to halve is always the same) → first order. For first order, ln[A] vs t gives a straight line (gradient = −k). For second order, 1/[A] vs t gives a straight line. For zero order, [A] vs t is a straight line (constant rate of decrease). Method 3 (Rate-concentration graph): plot rate vs [A]. If straight through origin → first order. If curve through origin → second order. If horizontal line → zero order.
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