Question

How in Irrverisible process Entropy of universe increased and how contant in reversible process in CHemsitry

Answer 1

Entropy of the universe increases in an irreversible process because these spontaneous natural processes inherently lead to greater disorder and dispersal of energy/matter, a principle defined by the Second Law of Thermodynamics ($\Delta S_{universe} > 0$). In contrast, for an idealized reversible process, the entropy of the universe remains constant ($\Delta S_{universe} = 0$). This is because any gain in entropy by the system is precisely counterbalanced by an equal loss of entropy from the surroundings, or vice versa, maintaining a net zero change ($\Delta S_{system} = -\Delta S_{surroundings}$).

Answer 2

Entropy measures disorder. The total entropy of the universe ($\Delta S_{universe}$) is the sum of the system's and surroundings' entropy changes: $\Delta S_{universe} = \Delta S_{system} + \Delta S_{surroundings}$.

• Irreversible Process: Spontaneous processes increase $\Delta S_{universe}$ because they lead to greater dispersal of energy/matter and randomness.
• Reversible Process: Idealized, infinitely slow processes result in $\Delta S_{universe} = 0$, where system and surroundings entropy changes cancel out ($\Delta S_{system} = -\Delta S_{surroundings}$).

A reversible process is an idealized, hypothetical process that occurs infinitely slowly, such that the system remains in thermodynamic equilibrium with its surroundings at every infinitesimal step. Such a process can be reversed by an infinitesimal change in conditions, returning both the system and surroundings to their initial states without any net change in the universe. For a reversible process, the total entropy change of the universe is zero: $\Delta S_{universe} = 0 \quad \text{(for reversible processes)}$ This zero change implies that any entropy gained by the system is exactly compensated by an equal amount of entropy lost by the surroundings, or vice versa: $\Delta S_{system} = -\Delta S_{surroundings}$ Irreversible processes are spontaneous processes that occur naturally in a single direction and cannot be reversed without external intervention. For any spontaneous (irreversible) process, the total entropy of the universe always increases: $\Delta S_{universe} > 0 \quad \text{(for irreversible processes)}$ This increase occurs because irreversible processes lead to a greater dispersal of energy and matter, increasing the number of accessible microstates. Natural processes tend to move towards states of higher probability and greater disorder.