Calculate the work done in polyatomic gas

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SUMMARY

The discussion focuses on calculating the work done during an irreversible adiabatic expansion of 2 moles of a polyatomic gas with a heat capacity ratio (γ) of 4/3, starting at 300K and 10 atm pressure, expanding to 1 atm. The formula for work done in an adiabatic process is W = nCvΔT, where Cv is derived as R/(γ-1). The final answer provided is 405R, but participants highlight the challenge of determining the change in temperature due to unknown final temperature and volume. The relationship PV^γ = constant is noted as applicable for adiabatic processes, but its relevance in irreversible processes is questioned.

PREREQUISITES
  • Understanding of adiabatic processes in thermodynamics
  • Familiarity with the ideal gas law
  • Knowledge of heat capacity ratios (γ) for different gas types
  • Basic algebra for manipulating equations
NEXT STEPS
  • Study the derivation and application of the formula W = nCvΔT in adiabatic processes
  • Learn how to apply the ideal gas law to find final temperature and volume in adiabatic expansions
  • Research the differences between reversible and irreversible adiabatic processes
  • Explore the implications of the heat capacity ratio (γ) on work done in gas expansions
USEFUL FOR

This discussion is beneficial for students and professionals in thermodynamics, particularly those studying gas laws and adiabatic processes, as well as anyone involved in engineering or physical sciences requiring a deeper understanding of gas behavior during expansion.

paragchitnis
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Homework Statement


Calculate the work done by the system in an irreversible (single step) adiabatic expansion of 2 moles of a polyatomic gas (\gamma = 4/3) from 300K and pressure 10 atm to 1 atm.


Homework Equations


Work done in adiabatic process
W = nCv\DeltaT
n = Moles of gas
Cv = R/(\gamma-1) R-Universal gas constant
\DeltaT- Change in absolute temperature

The Attempt at a Solution


The given answer is 405R. I am unable to find out the change in temperature as final temperature and volume are unknown. Is there any other formula to calculate the work done in adiabatic expansion?
 
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Are you aware that P V^{\gamma} = constant for adiabatic processes? You can find the final temperature using this fact and the ideal gas equation of state.
 
Pi-Bond said:
Are you aware that P V^{\gamma} = constant for adiabatic processes? You can find the final temperature using this fact and the ideal gas equation of state.

I think PV\gamma= constant is applicable for adiabatic reversible processes only. It is irreversible process..
 

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