# A universal constant?

bomba923
Is the Ideal Gas Constant a universal constant?
*If not, then what is it relative to?

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gravenewworld
I'm not sure what you mean by the Real Gas constant.
The ideal Gas constant R is universal
If you are refering to the vander waal equation that describes real gases and the constants a and b, then no, both a and b are not universal constants. You have to determine a and b experimentally and measure critical temperatures and critical pressures with respect to the compound in question.

Homework Helper
universal constant, e.g. the speed of light c, where it supposedly holds true at all inertial frames of reference...everywhere.

I don't believe that R is a universal constant.

gravenewworld
Why isn't R is a universal constant for an ideal gas? When does it ever change?

bomba923
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Homework Helper
no I guess not, but before you go on to call it universal (as the speed of light is "universal) you might want to bring it up in one of the physics subforums

bomba923
GCT said:
no I guess not, but before you go on to call it universal (as the speed of light is "universal) you might want to bring it up in one of the physics subforums

!Why--exactly? How what does bringing up it a different forum have to do with the Ideal Gas Constant being universal/"calling it universal"??
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But I agree, physics and engineering do often use the Ideal Gas Constant, and it easily could have been a question in one of the physics subforums . I posted this in chemistry because I worked with the Ideal Gas Constant most frequently in my chemistry courses.

Homework Helper
GCT said:
no I guess not, but before you go on to call it universal (as the speed of light is "universal) you might want to bring it up in one of the physics subforums

$$R=k_{B} N_{A}$$

Boltzmann's constant is universal, Avogadro's number is universal, ergo the ideal gases' constant is universal.

Daniel.