Thermodynamics, Kinetics, Equilibrium and Electrochemistry
What you must understand
Thermodynamics: enthalpy change ΔH (exothermic negative, endothermic positive), Hess's law, bond energies, entropy ΔS and Gibbs energy ΔG = ΔH − TΔS. A reaction is spontaneous when ΔG < 0. Calorimetry: q = mcΔT.
Kinetics: collision theory, activation energy, effect of concentration, temperature, surface area, pressure and catalyst on rate. Distinguish rate from yield; catalysts lower activation energy without changing ΔH or equilibrium position.
Equilibrium: dynamic equilibrium, Le Chatelier's principle, equilibrium constant K. Predict shifts with changes in concentration, pressure, temperature, catalyst.
Electrochemistry: oxidation at the anode, reduction at the cathode. Galvanic cells convert chemical to electrical energy; electrolysis uses electrical energy to drive reactions. Standard electrode potentials predict cell voltage and spontaneity (E°cell = E°cathode − E°anode).
Traps
Catalysts do not shift equilibrium or change yield - only speed. Increasing pressure shifts equilibrium toward fewer gas moles. Exothermic reactions are not always spontaneous (entropy matters). Watch sign conventions for ΔH and electrode potentials.
Rule of thumb
For a spontaneous galvanic cell, E°cell must be positive - the more positive potential is the cathode.
Worked example
Zn/Cu cell: E°(Cu²⁺/Cu) = +0.34 V, E°(Zn²⁺/Zn) = −0.76 V. E°cell = 0.34 − (−0.76) = 1.10 V, positive, so the reaction is spontaneous.