Question

Why does entropy increase in an irreversible process?

Answer 1

Entropy:

1. Entropy is independent of the path for changing the state and it is responsible for measuring the randomness of a system.
2. In an irreversible process, in addition to this exchange of entropy with the surroundings, there is also entropy generated within the system itself.
3. In the irreversible case the applied pressure exceeds the internal pressure so there is a mismatch and less work is done on the gas than in the reversible case.
4. No heat is exchanged in the surrounding in the irreversible adiabatic process but there is a requirement for change in entropy.
5. As entropy is a state function, whether the process is reversible or irreversible, there is no difference in change in entropy of the system.
6. Energy always flows downhill which increases the entropy.
7. An irreversible process is defined as a process that cannot be reversed, a process, that cannot return both the system and the surroundings to their original conditions.
8. Also, the entropy increases with the increase in the number of energy levels.
9. Energy increases the entropy of the system.
10. Presence of friction and heat losses. In real thermodynamic systems or in real heat processes, we cannot exclude the presence of mechanical friction or heat losses
11. During the irreversible process, the entropy of the system increases. There are many factors that make a process irreversible:
12. When there is a rise in the volume of a system at constant energy more energy level is occupied
13. $S$ represents entropy, so for the irreversible process, the change in entropy is$\mathrm{\Delta }{S}_{irreversible}>0$, $S=\frac{dQ}{T}$ $dQ$ represents a change in heat and$T$ represents temperature.
14. This formula states that the variation of entropy of a system between the states $A$ and $B$ can always (even for irreversible "real" transformations) be gotten by the integral of $\delta Q_{rev}/T$ along any reversible path that goes from $A$ to $B$.
15. For instance, the path can be a combination of isothermal, isobaric and isothermal transformations; it does not matter as long as the path goes from $A$ to $B$.
16. If you consider an initial state $A$ that undergoes either:
17. A reversible adiabatic transformation to a state $B_r$
18. An irreversible adiabatic transformation to a state $B_i$