Gas Constant: Does Pressure or Temperature Affect R?

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Discussion Overview

The discussion centers around the nature of the gas constant (R) in relation to the ideal gas law, specifically whether temperature or pressure affects its value. Participants explore theoretical implications and practical applications related to gas behavior under varying conditions.

Discussion Character

  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant questions if the gas constant changes with varying pressure (e.g., 25kPa vs. 100kPa) while working on an assignment related to turbine blades.
  • Another participant asserts that the universal gas constant is indeed a constant and not a function of temperature, suggesting that deviations from the ideal gas law are due to correction terms related to intermolecular forces and molecular volume.
  • It is noted that while R is constant, the equation of state that relates pressure, volume, and temperature can vary, with the ideal gas law being a simplified model.
  • A later reply confirms that the gas constant remains at 287 Jkg/K regardless of atmospheric pressure or temperature, indicating these variables do not influence the calculation of R.

Areas of Agreement / Disagreement

Participants generally agree that the gas constant itself does not change with pressure or temperature. However, there is a discussion about the implications of the ideal gas law and its limitations, indicating some level of debate regarding the broader context of gas behavior.

Contextual Notes

The discussion does not resolve the complexities of gas behavior under non-ideal conditions or the specific contexts in which the ideal gas law may fail, leaving open questions about the applicability of R in various scenarios.

Who May Find This Useful

This discussion may be useful for students and professionals working in fields related to thermodynamics, fluid mechanics, and engineering, particularly those dealing with gas behavior in practical applications.

The Chase
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Hi there,

I've had an assignment recently about turbine blades which involved lots of calculations with the gas constant (R). Working away at my report I came across the ideal gas law that use the gas constant in its equation, and I was wondering if temperature or air pressure effect the Gas constant at all? For example would the gas constant change if pressure was 25kPa as opposed to 100kPa?

Thanks in advance!
 
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From my understanding the universal gas constant itself is a constant.

The departure of the ideal gas law is expressed as correction terms to the pressure and volume due to intermolecular forces and the fact that molecules do occupy some space rather than being point particles. R is not a function of temperature.

See here:
http://hyperphysics.phy-astr.gsu.edu/hbase/kinetic/waal.html#c1
 
R is a constant, by definition.

What is not "constant" is the equation of state, which links the gas pressure, volume, and temperature. The "ideal gas law" PV = nRT is the simplest equation of state and accurate enough for many purposes, but there have been many improvements to it.
http://en.wikipedia.org/wiki/Equation_of_state
 
So the gas constant itself will always remain at 287 Jkg/K despite atmospheric pressure/temperature? As these variables are not used in the calculation of R?
 

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