One mole of a monatomic ideal gas is taken along two cyclic processes E → F → G → E and E → F → H → E as shown in the PV diagram. The processes involved are purely isochoric, isobaric, isothermal or adiabatic. Match the paths in List I with the magnitudes of the work done in List II and select the correct answer using the codes given below the lists. List I: P. G → E; Q. G → H; R. F → H; S. F → G. List II Options: (1) P→4, Q→3, R→2, S→1; (2) P→4, Q→3, R→1, S→2; (3) P→3, Q→1, R→2, S→4; (4) P→1, Q→3, R→2, S→4.
Answer: A.
Or read the worked solution below. Jump to the steps ↓
Written solution
Step 1: Identify the states and processes from the diagram.
For 1 mole of a monatomic ideal gas, the adiabatic index is . From the given diagram, the coordinates of the states are:
The states and lie on the isobaric line . The processes are identified as:
- : Isochoric
- and : Isobaric
- : Isothermal
- : Adiabatic
Step 2: Calculate the work done for path S ().
Since is an isothermal process, the temperature remains constant:
The work done during this isothermal expansion is:
Thus, S matches with 1.
Step 3: Calculate the work done for path R ().
Since is an adiabatic process:
Substitute :
The work done during this adiabatic expansion is:
Thus, R matches with 2.
Step 4: Calculate the magnitude of work done for path Q ().
Since is an isobaric process at pressure :
The magnitude of the work done is:
Thus, Q matches with 3.
Step 5: Calculate the magnitude of work done for path P ().
Since is an isobaric process at pressure :
The magnitude of the work done is:
Thus, P matches with 4.
Answer: The correct matching is: P 4, Q 3, R 2, S 1