Is the Boltzman constant really constant for all gases???

Question

Is the Boltzman constant really the same for all gases. After all the mass of the Chlorine molecule is about 35 times that of the hydrogen molecule

Answer 1

The Boltzmann constant is a way to relate kinetic energy to heat.

I think you're picturing Chlorine molecules vibrating "as much" as Hydrogen molecules. However, the Chlorine molecules can vibrate "less" and still be just as energetic as the Hydrogen molecules. Keep in mind that kinetic energy is a product of mass and velocity. An increase in mass can maintain the same kinetic energy with lower agitation.

It may be helpful to see the source below. The subsection "Application to simple gas thermodynamics" in the section "Role in the equipartition of energy" somewhat addresses your concern. You'll see how k*T really represents the energy in the system. Thus, higher temperatures have more impact on the average velocity of particles of less mass.

Answer 2

Boltzmann constant k = R/Na, where R = 8.314 J/mol*K, the constant from the state equation of gases and Na = 6.02*10^23 the Avogadro's number. So, yes the Boltzmann constant is the same for all gases.

Answer 3

it wouldnt be acalled a constant if it wasnt constant.
it may not be exacly the same but it works for mathamatical purposes