This lecture covers the equilibration of redox reactions by assigning oxidation degrees, identifying species exchanging electrons, and describing the transfer of electrons. It also discusses the conservation of atoms, the first principle of thermodynamics, internal energy, and the relationship between state variables. The concepts of enthalpy, exothermic and endothermic processes, and the calculation of standard enthalpies of reaction are explained. The lecture further explores the Hess law, enthalpy changes in reactions, and the calculation of enthalpy from bond enthalpies. Examples and methods for calculating enthalpy, including the ethyne formation reaction, are provided.