Question

In thermodynamics, a process is called reversible when:
A. Surroundings and system change into each other
B. There is no boundary between system and surroundings
C. The surroundings are always in equilibrium with system
D. The system changes into the surroundings spontaneously

Answer 1

Hint: A process is said to be reversible when occurs by an infinitesimal change in the state of functions. The terms surroundings and system are interrelated to each other but are entirely opposite to each other. System is something which we are observing and surrounding is an environment except for the system.

Complete step by step answer:
Let us talk about reversible process and its conditions:
- A reversible process is a process which can be turned into either direction by inducing infinitesimal changes in the system through its surroundings.
- Reversible process is something that after it has taken place, it can be reversed and when reversed, allows the system and its surroundings to return to their initial states.
- In reversibility equilibrium operates at quasi equilibrium. The process is done in such a way that the equilibrium terms and conditions are maintained at each step.
- During the reversible process, the system is in thermodynamic equilibrium with its surroundings. On being reversible, it does not leave any change in either the system or the surroundings. Since it takes an infinite time for a reversible process to finish, hence, perfectly reversible processes are not possible.
The correct answer of this question is in thermodynamics, a process is called reversible when the surroundings are always in equilibrium with system.
So, the correct answer is “Option C”.

Note: There is equilibrium between system and surroundings only in reversible process, in irreversible processes, the volume or pressure of the system does not have the time to reach equilibrium as changes in system occur instantaneously and dramatically.