I understand activation energy to be the relative difference in energy between that of the activated complex/transition state (at some temperature) and the average energy of the reactants like shown here:
(Source: Wikimedia, User Bkell)
If this is correct, I have questions about graph like this one:
(Source: webchem.net (not available anymore, Internet Archive), retrieved via the Internet Archive)
Is the location marked activation energy supposed to be the energy level of the transition state provided the energy axis is absolute?
Can the Maxwell-Boltzmann distribution be done for heterogeneous systems (i.e., two chemical reactants)?
Unrelated to the graph, why does negative activation energy result in a decrease in reaction rate (per Arrhenius equation)?