Molecules are reduced when hydrogens are added and oxygens removed. This also increases their energy. Why?

Question

When molecules are reduced they generally gain energy. If reduction involves the addition of electrons, then the electrons add their energy to the molecule. However, a molecule is also reduced simply by adding hydrogens and removing oxygens. This does not add the energy of new electrons since the number of electrons does not change (assuming that the number of bonds doesn't change). Why then should the energy necessarily be higher simply because hydrogens have been substituted for oxygens? Example: Methane (CH4) has more energy than Carbon dioxide (CO2). Same number of bonds in each, carbons being double-bonded to each oxygen in CO2.

Answer 1

The energies of CH4 and CO2 have nothing to do with reduction (or oxidation). Putting in hydrogens and taking oxygens is completely different than adding and removing electrons. Molecules are not "reduced" simply because their energies increases. One reason that CH4 has a higher energy than CO2 is the different bonding structures of the two. CH4 has four sigma bonds, and CO2 has two sigma bonds and two pi bonds (because of the double bond.) Pi bonds are generally weaker than sigma bonds, hence the lower energy in CO2.

Answer 2

The Hydrogen atoms are electron donors. They like to give up their electrons and therefore provide energy. Oxygen is an electron acceptor. It needs 2 electrons to complete its outer shell and therefore is happy receiving electrons. Since we live in an oxidative universe, removing electrons provides energy (oxidation). Reduction requires energy. When removing oxygen, the 2 electrons oxygen would normally have accepted are now added back to the other molecule (like carbon).

Answer 3

I am not convinced that your observations are correct. The energy of FORMATION may be higher with methane than with CO2, but the reaction with oxygen that creates CO2 (and water) releases energy that is not devoted to the formation of those compounds.