Oxidation number or oxidation state denotes the number of electrons lost or gained by an atom when it forms a chemical bond with another atom.
In general:
-the oxidation number for a free element is zero
- the oxidation number for H = +1 when attached to non-metal and -1 when attached to a metal
-The oxidation number for O is -2 most of the time
- for a neutral molecule, the sum of the oxidation number = 0
The given reaction is:
CO + 2H2 → CH3OH
1) In CO, the oxidation number of C = +2 and O = -2
2) In H2, the oxidation number of H = 0
3) In CH3OH, the oxidation number of C = +1, H = +1 and O = -2