Question

At equilibrium the change in Helmholtz free energy is :

• A. equal to zero
• B. less than zero
• C. greater than zero
• D. both $A$ and $C$

Answer 1

The correct option is B less than zero

In thermodynamics, the Helmholtz free energy is a thermodynamic potential that measures the “useful” work obtainable from a closed thermodynamic system at a constant temperature and volume. The negative of the difference in the Helmholtz energy is equal to the maximum amount of work that the system can perform in a thermodynamic process in which volume is held constant. For a system at constant temperature and volume, the Helmholtz energy is minimized at equilibrium.