Standard Enthalpy of Formation - Exothermic?

[alebeau]

Hello, I have a conceptual question about enthalpies of formation I hope you can assist me with.

Given that the enthalpy of reaction is typically negative, does that suggest that the product formed is lower in energy than the reactants?

For example,

O2 + 1/2 C (graphite) --> CO2. ΔH f =393.5 kJ/mol

That seems odd to me. Based on the negative ΔH, it would appear as though CO2 was indeed lower in energy than molecular oxygen and carbon (graphite) as the reaction is exothermic. However, this seems counter-intuitive? Can anyone please explain?

Thanks

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Charcoal catches fire! Carbon dioxide does not turn back into charcoal.