Question

Why does a reduced compound have more potential energy than an oxidized compound?

Answer 1

First, remeber this is not univeral fact that reduced compounds have more energy than oxidised, e.g ATP has mor energy than ADP. Lets talk of oxidation of fuels. When a compound is oxidised some bonds are broken and some new bonds are formed. Usualy what happen is

C-H bond is oxidised to C=O bonds. In any reaction if the new bonds formed are weaker than reactant bonds ENERGY WILL BE ABSORBED. And if new bonds are stronger ENERGY WILL BE RELEASED. In the bove oxidation the product bonds (OXIDISED COMPOUNDS) have stronger bonds and hence lower POTENTIAL ENERGY than the reactants (REDUCED COMPOUNDS).Here REDUCED COMPOUNDS have weaker bonds hene more POTENTIAL ENERGY.