Final answer:
The chemical potential μ of a pure substance is the Gibbs energy (A), which is defined as G=H-TS and offers insight into the spontaneity of chemical reactions and system equilibria at constant temperature and pressure.
Step-by-step explanation:
The chemical potential μ of a pure substance is the Gibbs energy. The Gibbs energy, also known as the Gibbs function or Gibbs potential, is denoted by the symbol G and is defined as G=H-TS, where H is the enthalpy and TS represents the product of the temperature (T) in Kelvins and the entropy (S) of the system. This thermodynamic quantity provides a criterion for predicting the direction of a chemical reaction and the equilibrium composition of a system.
Understanding the Gibbs energy is important in thermodynamics and chemistry, as it allows for the examination of processes that occur at constant temperature and pressure. The change in Gibbs energy is used to determine whether a process will occur spontaneously; a negative change (ΔG<0) indicates a spontaneous process under constant temperature and pressure.
The enthalpy (H) is the sum of a system's internal energy plus the product of its pressure and volume. On the other hand, entropy (S) is a measure of the 'dilution' of thermal energy and changes with temperature. At 0 K, according to the Third Law of Thermodynamics, a perfectly ordered solid has an entropy of zero. However, as temperature rises, so does the entropy.