Question

Which of the following statements is correct for any thermodynamic system?
(A) The internal energy changes in all processes.
(B) Internal energy and entropy are state functions.
(C) The change in entropy can never be zero.
(D) The work done in an adiabatic process is always zero.

Answer 1

Hint: for answering this we will use the elimination method and will eliminate the wrong option. Keeping in mind that in a thermodynamic system for some processes internal energy changes. State functions are those whose value does not depend on the path taken but only on the final and initial position. for some process change in entropy and work done can be zero.

Complete Step By Step Answer:
A thermodynamic system is a system that is separated from its environment by actual or hypothetical walls.
In a thermodynamic system, the internal energy of a system is the energy that is contained within the system; only kinetic energy and potential energy are excluded. Internal energy is a function of temperature that is if temperature changes internal energy changes. So processes in which temperature is kept constant internal energy does not change.
Hence option A) is incorrect.
In thermodynamics, state function is referred to as property whose value is independent of the path taken to reach a specific value. Internal energy and entropy are measured by initial and final states. In this, any number of steps gives us the same value. So internal energy and entropy are state functions.
Hence, option B) is the correct answer.
Change in entropy is the difference between entropy at the final state and entropy in the initial state. During a process, if there is no change in the state of a system, entropy will be zero.
Hence option C) is incorrect.
In thermodynamics, if a process is taking place under constant volume then work done will be zero. In the adiabatic process, the total heat of the system is kept constant, not the volume.
Hence option D) is incorrect.
Hence, option B) is the correct answer.

Note:
 for isothermal, free expansion, and cyclic process internal energy is zero. Density is a state function. For a reversible process change in entropy is zero. In isochoric process work done is zero as it is under constant volume.