2.2 Reversible and Irreversible Processes

  Thermodynamics and Thermochemistry

    1.0 Introduction to Thermodynamics
    2.0 Thermodynamic Processes
    3.0 Heat $(Q)$
    4.0 Work $(W)$
    5.0 Internal Energy
    6.0 Zeroth Law of Thermodynamic
    7.0 First Law of Thermodynamics
    8.0 Heat Capacity
    9.0 Enthalpy $(H)$ or Heat Content
    10.0 Significance of $?H$ and $?E$
    11.0 Relationship Between $?H$ and $?E$
    12.0 Standard Enthalpy of Reaction
    13.0 Law of Thermodynamics
    14.0 Bond Energy or Bond Enthalpies
    15.0 Second Law of Thermodynamic
    16.0 Entropy (S)
    17.0 Spontaneous Processes
    18.0 Free Energy (G)
    19.0 Enthalpy, Entropy, Free Energy Changes and The Nature of Process
    20.0 Standard Free Energy Change
    21.0 Coupled Reactions
    22.0 Third Law of Thermodynamic
    23.0 Important Facts

---

2.2 Reversible and Irreversible ProcessesIn thermodynamics, a process is said to be reversible when energy change in each step of the process can be reversed in direction by changing the variables such as pressure, volume or temperature acting on them. Here the process is carried out in infinitesimally slowly such that at every stage the system is in pressure and temperature equilibrium with its surrounding, In such a process the driving and opposing forces differ infinitesimally and the process can be reversed completely by increasing the opposing force by an infinitesimally amount. Any process which does not take place in an above-mentioned manner is said to be an irreversible process the driving and opposing force differs by a large amount. The fact that the process is irreversible does not mean that the system cannot be restored to the original state. The water that has come down to the ocean can be taken to the top of the hill but such reversals would involve work by the surrounding or external agencies greater than that is obtained during the forward change.