Question

Define reversible process.

Answer 1

Hint: Reversible process means the process that has the capability of being reversed so that the previous state is again attainable. The symbol $ \rightleftharpoons $ is used for reversible reactions like for example:
$N{H_4}Cl \rightleftharpoons N{H_3} + HCl$ (Decomposition of ammonium chloride is a reversible process)

Complete answer:
We see so many changes in our daily life happening around us like boiling of water, burning of paper, melting of ice etc. In some of the cases the system and surroundings can be brought back to its initial state but in some cases it is not possible.
Hence reversible process is defined as the process that can be reversed without leaving any impact on the surroundings. It means both the system and surroundings can be returned to their initial states at the end of the reversible process. There is no change in the thermodynamic properties like temperature, pressure and volume.
A process is said to be reversible if a change is brought about in such a way that the process could, at any moment be reversed by an infinitesimal change.
In a reversible process, the opposing force is infinitesimally smaller than the driving force and an infinitesimal change in the opposing force can reverse the process.
A reversible process is considered to proceed from initial to final state through infinite series of infinitesimally small stages and it is virtually in state of equilibrium.
A reversible process is considered to be an ideal process.
During the reversible process all the changes that occur in the system are in thermodynamic equilibrium with each other.
Few examples of Reversible process:
-Frictionless motion of solids.
-Extension of springs.
-Slow isothermal compression or expansion of gases.

Note:The machine is in thermodynamic equilibrium with its surroundings during the whole reversible phase.
It leaves no difference in either the system or the surroundings after being reversed.
Because the reversible method will take an endless length of time to complete.
Perfectly reversible procedures are unlikely.
However, the difference from reversibility can be negligible if the device undergoing the modifications reacts much faster than the changes applied.