Final answer:
Helmholtz Free Energy is a thermodynamic potential that measures the useful work that can be extracted from a system at constant temperature and volume. It is a state function and relates to the spontaneity of a process. In a reversible process, the change in Helmholtz Free Energy is zero, while in an irreversible process, it is positive.
Step-by-step explanation:
Helmholtz Free Energy, also known as Helmholtz energy, is a thermodynamic potential that measures the useful work that can be extracted from a system at constant temperature and volume. It is denoted by the symbol F or A, and is related to the enthalpy and entropy of the system by the equation F = U - TS, where U is the internal energy, T is the temperature, and S is the entropy.
Helmholtz Free Energy is a state function, which means that its value depends only on the current state of the system and not on the path taken to reach that state. It is related to the spontaneity of a process - if the change in Helmholtz Free Energy is negative, the process is spontaneous; if it is positive, the process is non-spontaneous.
In a reversible process, the change in Helmholtz Free Energy is zero, indicating that the system is in equilibrium and no useful work can be extracted. However, in an irreversible process, the change in Helmholtz Free Energy is positive, indicating that some of the system's work potential has been lost as heat.