What is the Equation of State for an Ideal Gas?

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SUMMARY

The equation of state for an ideal gas is represented by the relation p = ρc_s², where p is pressure, ρ is density, and c_s is the speed of sound. This equation applies specifically to an ideal isothermal gas. The discussion also references the ideal gas law pV = NkT, which can be reformulated to p = ρkT, indicating that c_s² equals k_BT under certain conditions. However, it is crucial to note that the density (ρ) in these equations refers to different quantities, with the first potentially involving mass density and the second referring to number density, highlighting the need for clarity regarding molar mass and the adiabatic index (γ).

PREREQUISITES
  • Understanding of ideal gas laws, specifically pV = NkT
  • Familiarity with the concepts of pressure, density, and speed of sound in gases
  • Knowledge of thermodynamic principles, particularly isothermal processes
  • Basic grasp of the adiabatic index (γ) and its significance in gas equations
NEXT STEPS
  • Research the derivation of the equation of state for ideal gases
  • Study the relationship between speed of sound and temperature in gases
  • Explore the implications of the adiabatic index (γ) on gas behavior
  • Examine the differences between mass density and number density in thermodynamics
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Students and professionals in physics and engineering, particularly those focusing on thermodynamics, fluid dynamics, and gas behavior in various applications.

Niles
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Homework Statement


Hi

Often I bump into the relation [itex]p=\rho c_s^2[/itex], where p is the pressure, rho the density and cs the speed of sound in the ideal gas. It is apparently called the equation of state for an ideal isothermal gas.

I know about [itex]pV=NkT[/itex], which becomes [itex]p=\rho kT[/itex], but does this mean that [itex]c_s^2=k_BT[/itex]?
 
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The ρ in your two equations is not the same quantity.
In the first equation it may be mass density (but it looks like you are missing a γ), in the second is number density. But again, the molar mass is missing.
 

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