Is my answer correct for finding the change in entropy?

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SUMMARY

The discussion focuses on calculating the change in entropy for an ideal gas during a reversible compression process. The user correctly identifies that the formula for entropy change at constant temperature simplifies to S = nR ln(V2/V1). Given that the volume ratio V2/V1 equals 1/3 due to the pressure increasing to three times the original, the final expression for entropy change is S = nR ln(1/3). The user’s approach and calculations are confirmed as correct.

PREREQUISITES
  • Understanding of the ideal gas law and its parameters.
  • Familiarity with the concepts of entropy and thermodynamic processes.
  • Knowledge of the specific heat capacities, particularly Cv for ideal gases.
  • Basic logarithmic functions and their properties.
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  • Study the derivation of the ideal gas law and its applications in thermodynamics.
  • Learn about the relationship between pressure, volume, and temperature in reversible processes.
  • Explore the concept of entropy in greater detail, including its implications in thermodynamic cycles.
  • Investigate the role of specific heat capacities in calculating changes in thermodynamic systems.
USEFUL FOR

This discussion is beneficial for students and professionals in thermodynamics, particularly those studying ideal gas behavior, entropy calculations, and reversible processes in physics and engineering.

aruwin
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I am not sure if my work is correct so I need your help to confirm it.

Question:
Find the change in entropy when:

n mol of ideal gas (ɣ=7/5) is reversibly compressed until the pressure is three times the ideal gas at constant temperature.

My answer:
S=n Cv ln(T2/T1) + nR ln(V2/V1)

as temperature is constant so

S=nR ln(V2/V1)
V2/V1=1/3
 
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aruwin said:
I am not sure if my work is correct so I need your help to confirm it.

Question:
Find the change in entropy when:

n mol of ideal gas (ɣ=7/5) is reversibly compressed until the pressure is three times the ideal gas at constant temperature.

My answer:
S=n Cv ln(T2/T1) + nR ln(V2/V1)

as temperature is constant so

S=nR ln(V2/V1)
V2/V1=1/3
Look right to me.

AM
 

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