Which elements are oxidized? Which elements are reduced?

Question

CH3CH2OH(l)+3O2(g)→3H2O(l)+2CO2(g)

Answer 1

The oxidation state of oxygen in O₂ is zero.  (True for all single elements).  The oxidation state of oxygen in CO₂ and in H₂O is -2.  Going from ox state 0 to -2 is gaining electrons = reduction.  So what is being oxidized?  Hydrogen maintains a +1 oxidation state throughout the reaction, so lets look at C.  There are 2C, 6H and 1O in the alcohol.  Oxygen is almost always -2 in a compound, hydrogen is almost always +1 in a compound, so lets figure C ox state.

 2x + 6(+1) + 1(-2) =0

Ox state of C in alcohol = +2.  How about C in CO₂?  Again, oxygen is -2 in this compound so  2(-2) + x = 0.  Carbon has an oxidation state of +4 in carbon dioxide.  C goes from oxidation state +2 to +4, meaning it lost electrons = oxidation

Answer 2

CH₃-CH₂-OH is structurally H₃C-CH₂-O-H where Hydrogen in -OH (alcohol group) has affinity to be oxidized by Oxygen (O₂) in vicinity. After the Hydrogen atom from -OH group gets loose the free electron in -O- pulls the Hydrogen atoms from nearby =CH₂ cluster. Thus the Hydrogen atoms in  =CH₂ are oxidized by Oxygen (O₂) in vicinity. Thus free negative charges of -O- and and =C= pulls farther apart Hydrogen atoms from H₃C- cluster and then loose Hydrogen atoms from H₃C- cluster are  oxidized by Oxygen (O₂) in vicinity. Then the remaining Oxygen atoms in vicinity couples up with tetravalent carbons, hence the carbons are also oxidized. Only oxygen atoms with highest electron affinity is being reduced.