Question

Gibbs' free energy is given by:
1 G = H - TS
2 G= H + TS
3 G = U + H - TS
4 G = U-TS​

Answer 1

In thermodynamics, the Gibbs free energy is a thermodynamic potential that can be used to calculate the maximum of reversible work that may be performed by a thermodynamic system at a constant temperature and pressure. The Gibbs free energy ({\displaystyle \Delta G=\Delta H-T\Delta S}{\displaystyle \Delta G=\Delta H-T\Delta S}, measured in joules in SI) is the maximum amount of non-expansion work that can be extracted from a thermodynamically closed system (can exchange heat and work with its surroundings, but not matter). This maximum can be attained only in a completely reversible process. When a system transforms reversibly from an initial state to a final state, the decrease in Gibbs free energy equals the work done by the system to its surroundings, minus the work of the pressure forces.