The enthalpy of a thermodynamic system, denoted by H, can be determined with the help of the following equation:
H = U + PV
Where U is the internal energy of the system, P is the pressure, and V is the volume. As per the second law of thermodynamics, the entropy of an isolated system can never decrease, i.e. the entropy change in an isolated system can only be positive or zero. Therefore, a process can be feasible only when the change in the entropy of the universe is positive. This implies that any process that does not violate the second law of thermodynamics must create an increase in the entropy of the universe.