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 the system
(d) the system changes into the surroundings spontaneously

Answer 1

In thermodynamics, all the processes occur when the systems are in equilibrium and reversible reactions are those reactions in which the final state of the system can be again reversed back into its initial stage and vice -versa. Now identify the correct statement.

Complete step by step solution:
- First of all, let’s discuss what thermodynamics is. By the term thermodynamics we mean the branch of science which deals with the heat and the other forms of energy i.e. work and the relationship between them.
- On the other hand, reversible reactions are those reactions in which the reaction can be reversed i.e. the changes which occur in the system can be reversed back. The initial state of the system which gets converted into the final state of the system can be reversed back to its initial stage without affecting the system and surroundings.
- For the reversible reactions to occur, the system and the surroundings both should be in the state of equilibrium for the reactions to take place. If this condition is satisfied only then the thermodynamic system is said to be reversible.

Hence option (c) is correct.

Note: Thermodynamics is not concerned with how and at what rate these energy transformations are carried out but depends on the initial and final states of the system undergoing the change. Laws of thermodynamics are applied only when the system is in equilibrium.