# A universal constant?

1. Jul 8, 2005

### bomba923

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

Last edited: Jul 8, 2005
2. Jul 8, 2005

### 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.

3. Jul 8, 2005

### GCT

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.

4. Jul 8, 2005

### gravenewworld

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

5. Jul 8, 2005

### bomba923

Oh yes---that's right!
*It is also called, "The Universal Gas Constant"
(sorry--i guess that kind of answers the question)
_
*GTC, any contentions?

Last edited: Jul 8, 2005
6. Jul 9, 2005

### GCT

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

7. Jul 9, 2005

### bomba923

!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.

8. Jul 9, 2005

### dextercioby

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

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

Daniel.

9. Jul 9, 2005

### GCT

Well there you go.

I have to say I'm a bit unfamiliar with so called "universal constants" I've just taken my second semester of physics. I just thought there would be more to the universal constant concept and I didn't think it to be appropriate to accept it simply as some vague notion.

10. Jul 9, 2005

### dwilkerson

I pose another question: Will we ever know why all of the "universal" constants are constant? Haha, just kidding around!