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Re: [Phys-L] Energy & Bonds

Endo-thermic graphs (like this one: http://bit.ly/184Ow3E (full url below)) show the products with more energy than the reactants. This makes me wonder a couple of things.

First, what 'energy' is being plotted on the y-axis?

For endothermic reactions the vertical axis MUST be enthalpy because
of the definition of 'endothermic'.

Second, why is the product (which for an endothermic process has a higher 'energy' than the reactants) the more likely substance?

It's not, an equilibrium is reached. However, equilibrium is based on
free energy, not enthalpy, and is significantly more temperature
dependent than enthalpy.

It is common to create those graphs in either internal energy (U or
E), enthalpy (H), or free energy, (G or A). (No difference between U
and E; big difference between G and A.)


Dr. Roy Jensen
(==========)-----------------------------------------¤
Lecturer, Chemistry
E5-33F, University of Alberta
780.248.1808