Question

An ideal gas undergoes isothermal process from some initial state i to final state f. Choose the correct alternatives.

1. dU = 0
2. dQ= 0
3. dQ = dU
4. dQ = dW

Answer 1

a and d

Explanation:

First Law of Thermodynamics: It is a statement of conservation of energy in a thermodynamical process.

According to it, heat given to a system (∆Q) is equal to the sum of the increase in its internal energy (AIT) and the work done (AW) by the system against the surroundings.

∆Q = ∆U + ∆W

According to the first law of thermodynamics.

∆AQ = ∆U + ∆W but ∆U ∝ ∆T

∆U = 0   .....[As ∆T = 0]

∆Q = ∆W, i.e., heat supplied in an isothermal change is used to do work against external surroundings.

or if the work is done on the system then an equal amount of heat energy will be liberated by the system