[cliverlong]

Hi,

   I see lots of examples of the Maxwell-Boltzmann curve used in explaining activation energy and the effect of increasing temperature on reaction rate - due to a  greater proportion of reactants with at least the activation energy at the higher temperature.

    However, I'm trying to understand what are the units used on the axes. What is being measured?

Horizontal axis is usually given as kinetic energy: so that axis would have unit Joules (or KiloJoules etc.) or would it?
The vertical axis is labelled "number of particles".

Now I realise the M-B plot is a statistical curve, vertical values are "meaningless", it's areas under the curve that represent something. If I take a vertical slice between k.e. value E₁ and higher value E₂, then the area under the curve would represent those species with energy between E₁ and E₂ . But I'm still not seeing what units this quantity would be measured in. Particle-Joules? Mole-Joules?

This should be obvious but I just can't see through this.


Thanks

Clive

[Yggdrasil]

The area under the curve represents the probability of finding a particle with energy between E₁ and E₂.  This is equivalent to the fraction of particles with energy between E₁ and E₂ and it is also equivalent to the relative amount of time each particle spends traveling at a speed in that particular range (this is known as the ergodic hypothesis).