Question

Why is the activation energy of combustion so large compared with regular bonding?

Answer 1

heya ❕ here's your answer
see the attachment..
hope it helps you

Answer 2

I wanted to know why combustion requires an activation energy and I found this article (see this too). It says that molecular oxygen ground state is a triplet state (according to Hund's rules), and that prevents it from reacting with singlet molecules. It still says nothing about bonding in an excited state (where the product is not a singlet).

Now consider a free oxygen atom and another oxygen atom during the formation of dioxygen. Since each oxygen atom is a triplet then it's possible for the direct product to have spin 2, 1 or 0 (according to Wigner's rule). So in principle I expect to see either an excited oxygen molecule (not a triplet) or a triplet. The excited states could not deexcite directly since it would be a forbidden transition, but they can through collisions. Is this paragraph correct?

In any case, what makes the formation of oxygen molecules from oxygen atoms "easier" than combustion in the absence of activation energy? why can't oxygen and singlet molecules (fuel) bond to form an excited state and then deexcite to initiate combustion? or is the fact that a triplet and a singlet can't give a singlet product (that's the preferred state of the intermediate products from what I have read) a big impediment?