Universal gas, Boltzmann's constant

[Evilinside]

I understand the formulas involved and numerical values of these constants and in the respective units . However I'm still having troubling understanding exactly what it is these two constants define. Does Universal gas constant say that For every mol times Kelvin there is 8.315J ? I don't think that makes sense since an increase in kelvin should actually decrease the amount joules, since K is in the denominator, which I believe then defies a portion of kinetic theory. Then Boltzmann's constant is it saying that every atom will have 1.38x amount of joules per kelvin?

 

[FredGarvin]

R is defined by this relationship going back to the definition of enthalpy:

h = u + \frac{p}{\rho} and the form of ideal gas equation of state p =\rho RT You get:

h = u + RT

If you differentiate with respect to temperature:

dh = du + R dT

\frac{dh}{dT} = \frac{du}{dT} + R

From relations for ideal gases...

C_v = \frac{du}{dT} and C_p = \frac{dh}{dT}

we can say that C_p = C_v + R or

C_p - C_v = R

This is important because that says that for all ideal gasses, the difference between C_p and C_v is a constant.

 

[Evilinside]

oh, I don't think came across any formula concerning enthalpy yet but it makes sense in equation form.

 

[FredGarvin]

Enthalpy is a very useful term. If you get into thermodynamics you will become very familiar with it.