What do you mean by reversible and irreversible process? Give example.

Explanation

Reversible process:
  It is the process which can be retraced to the initial state in such a way that the system undergoes the same changes as occurred in the direct process.
  Example
i) Melting of ice
ii) Working substance taken along complete Carnot.s cycle.
Irreversible process
It is the process in which the system cannot be retraced to its original state.
Example
i) Rusting of iron. 
ii) Diffusion of gases
iii) Sudden expansion or contraction of a gas.