Thermochemistry

This chapter assesses thermochemistry, which is the study of energy released or absorbed as heat during chemical reactions and how it depends upon the conditions. Thermochemistry is a branch of thermodynamics because a reaction vessel and its contents form a system, and chemical reactions result in the exchange of energy between the system and the surroundings. The chapter begins by looking at enthalpies of physical and chemical changes. It explains Hess's law, according to which the standard reaction enthalpy is the sum of the values for the individual reactions into which the overall reaction may be divided. The chapter then considers the standard enthalpy of formation, as well as the temperature dependence of reaction enthalpies. It also discusses differential scanning calorimetry (DSC) and isothermal titration calorimetry (ITC).