Adiabatic expansion of an ideal gas

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SUMMARY

The discussion focuses on the adiabatic expansion of an ideal monatomic gas, specifically calculating the final pressure and the change in enthalpy after the volume is doubled. The relevant equation used is pVγ = constant, where γ (gamma) is the heat capacity ratio. The participants confirm that treating temperature as constant during the expansion is incorrect for part b, emphasizing the need to apply the correct thermodynamic principles for accurate calculations.

PREREQUISITES
  • Understanding of ideal gas laws
  • Familiarity with adiabatic processes
  • Knowledge of thermodynamic properties, specifically enthalpy
  • Concept of heat capacity ratio (γ) for monatomic gases
NEXT STEPS
  • Study the derivation and application of the adiabatic process equation pVγ = constant
  • Learn how to calculate changes in enthalpy for non-isothermal processes
  • Explore the implications of the first law of thermodynamics in adiabatic expansions
  • Investigate the behavior of ideal gases under varying conditions of pressure and volume
USEFUL FOR

Students and professionals in physics and engineering, particularly those studying thermodynamics and gas laws, will benefit from this discussion.

Elvis 123456789
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Homework Statement


An ideal monatomic gas has initial pressure Po and occupies initial volume Vo. The gas undergoes an adiabatic expansion in which the volume is doubled. Calculate in terms of Po and Vo

a) the final pressure of the gas

b) the change in its enthalpy during the expansion

Homework Equations


I posted two attachments with my attempted solutions. All the relevant equations are there. Just posting to see if anyone can spot anything wrong with my solutions. I feel fairly confident about part a, but not so much about part b.

The Attempt at a Solution

 

Attachments

  • thermo hw.png
    thermo hw.png
    76.3 KB · Views: 863
  • thermo hw b.png
    thermo hw b.png
    82.9 KB · Views: 904
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Elvis 123456789 said:
I feel fairly confident about part a, but not so much about part b.
In part b you treated T as constant during the process.
 
TSny said:
In part b you treated T as constant during the process.
Yeah that's the part I felt most uncomfortable about. Is this the right approach then, or do I have to go about it another way?
 
Elvis 123456789 said:
Yeah that's the part I felt most uncomfortable about. Is this the right approach then, or do I have to go about it another way?
Using the equation pVγ=const for adiabatic processes?
 
ehild said:
Using the equation pVγ=const for adiabatic processes?
yes that's it! thanks :)
 

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