[chimico]

Hello, i read that the oxidation of glucose by oxigen free energy, but if atoms only free energy when go from an higher energetic level to a lower and that energy is equal to the one needed to separe bonds, there should be no further energy because the force that oxigen use to oxidate it is the same energy relased!
What is the wrong thing in that ?

thank you

[Arkcon]

Well, I suspect this is one of those questions that ends up going in circles, but I'll bite ...

Hello, i read that the oxidation of glucose by oxigen free energy,

Yes, the oxidation of glucose using oxygen does release energy contained in the glucose and oxygen bonds.

but if atoms only free energy when go from an higher energetic level to a lower and that energy is equal to the one needed to separe bonds, there should be no further energy because the force that oxigen use to oxidate it is the same energy relased!
What is the wrong thing in that ?

thank you

Umm ... huh?  Maybe you're missing something here?  Maybe, if you have a textbook handy, you can try to fill it in, and ask a different question?

[chimico]

I mean... how is the energy stored in the chemical bonds of glucose? And where is the advantage if the energy that the oxigen needs to break the bonds is the same energy relased?

[kapital]

When you burn methanol, for example, (or any other substance) you get carbon dioxide and water, plus it heats up. In organisms it is similar, just that you dont want heat(but of curse it is generating) but chemical energey(ATP synthesis).

The more redused the compund is, more energy it can add. (glucose is more oxidased tha fats)

[Enthalpy]

You're perfectly right: reactants already form molecules before the reaction, and their bonds must first be broken. So a reaction (here a combustion) produces heat if the new bonds are stronger than the initial ones.

For instance, O=O isn't as strong a bond as H-O-H, and H-H isn't that strong neither, so combustion into H₂O releases much heat.

As opposed, N≡N is a very strong bond, so N₂ is little reactive and combining it with other elements produces little heat, or even absorbs some.

[chimico]

You mean energy is relased when an electron join an atom more electronegative than the original one?

[Bryan Sanctuary]

I mean... how is the energy stored in the chemical bonds of glucose? And where is the advantage if the energy that the oxigen needs to break the bonds is the same energy relased?

See quote above.

Bit of a misconception here.  No energy is stored in bonds.  It is the other way.  Simple example:

1 carbon and 4 hydrogen atoms        methane CH₄
        Higher energy                           lower energy

so methane has lower energy than its separated atoms. 

This means if you want to break a bond, you have to put energy into the bond.  You do not get energy out by breaking a bond.

So in your example, why is it exothermic?  Well your have stronger bonds in the reactants than the products.  So the difference between stronger bonds and weaker bonds is the energy released in a reaction and in this case is positive.

This is what thermochemistry is about.