Why does the Dry Air Gas Constant vary?

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SUMMARY

The discussion centers on the varying values of the dry air gas constant, with reported figures ranging from 286.9 to 287.22. Sources include The Engineering Toolbox, Physics Forums, Brisbane Hot Air Ballooning, and Wikipedia. The differences arise from variations in measurement methods and the molecular weight of dry air, which is 28.964. The universal gas constant is established at 8314.32, leading to a calculated dry air gas constant of approximately 287.056.

PREREQUISITES
  • Understanding of the universal gas constant (R = 8314.32 J/(kmol·K))
  • Knowledge of molecular weight of dry air (28.964 g/mol)
  • Familiarity with significant figures in scientific measurements
  • Basic principles of gas laws and thermodynamics
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  • Research the methods of calculating gas constants in different atmospheric conditions
  • Explore the impact of molecular weight variations on gas constant values
  • Learn about the significance of significant figures in scientific calculations
  • Investigate historical changes in measurement techniques for gas constants
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Students and professionals in physics, atmospheric science, and engineering who require a deeper understanding of gas constants and their implications in calculations.

Robert James Liguori
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I'm confused on why the dry air gas constant varies:
Can someone please explain why it differs and how it is constructed. Thanks, Robert

Reference:
[link to personal website removed]
 
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to within 3 significant figures these are all the same !
It would be worth checking how each source obtained the value, especially the date when the values were measured.
Methods vary and improve over the years
 
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I am not a physicist... so you are implying that the differences in the values is insignificant? To me, it should be exact... or a means should be in place to get the exact value at each given location of sampling... if this was indeed possible, which it may not be. Please advise.
 
universal gas constant = 8314.32 (in 1976 Standard Atmosphere)
molecular weight of dry air = 28.964

8.3143 / 28.964 = 0.28705634580859 (e.g., 287.056)
 
I figured it out... thanks for your help.

[link to personal website removed]
 
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Can you measure the length of your kitchen table exactly? Why not? Are you going to let that keep you from buying a tablecloth?

Even if the value of the gas constant is not exact, does that bring your calculations to a screeching halt (until you find the exact value, which doesn't exist)? Isn't 3 significant figures accurate enough for you?
 
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On these words of wisdom, the OP's question has been answered. Thread closed.
 

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