Kinetic Energy in relation to the ideal gas law

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SUMMARY

The discussion clarifies the relationship between kinetic energy and the ideal gas law, specifically addressing the average kinetic energy of monatomic and diatomic molecules. For monatomic molecules, the average kinetic energy is expressed as (3/2)kbT, while for diatomic molecules, it is (5/2)kbT. The ideal gas law, represented as PV = nparticleskbT, does not include these factors because pressure and energy density, although dimensionally similar, represent different physical quantities. Consequently, pressure multiplied by total volume does not equate to total energy, whereas energy density multiplied by total volume does.

PREREQUISITES
  • Understanding of kinetic energy and its relation to temperature
  • Familiarity with the ideal gas law (PV = nRT)
  • Knowledge of monatomic and diatomic molecular structures
  • Basic principles of thermodynamics
NEXT STEPS
  • Study the derivation of the ideal gas law and its assumptions
  • Explore the concept of energy density in thermodynamics
  • Learn about the equipartition theorem and its implications for different types of gases
  • Investigate the differences between pressure and energy density in physical systems
USEFUL FOR

This discussion is beneficial for physics students, educators, and professionals in thermodynamics, particularly those focusing on gas laws and molecular behavior.

vjk2
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I'm trying to fit this together.

For monotomic molecules, the avg kinetic energy is 3/2 k_b T

for diatomic, it is 5/2 k_b T

PV = n_particles * k_b T

Why is there no factor of 3/2 or 5/2 in the ideal gas law? How is it factored out?
 
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A simple answer might be that although pressure and energy density have the same dimensions, they are not the same quantity. For an ideal gas, its pressure and its energy density are not the same. Therefore:

pressure * total volume is not equal to total energy.

energy density * total volume is equal to total energy.
 

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