Assign an oxidation number to each element in the reaction

The question is incomplete, the complete question is;

Assign an oxidation number to each element in the reaction.

CO(g) + 2H2(g) → CH3OH(g)

In CO, the oxidation number of C is _, and that of O is _.

In H2, the oxidation number of H is _.

In CH3OH, the oxidation number of C is _, that of O is _, and that of H is _.

See explanation

Explanation:

If we look at the reaction, in CO, C is +2 while O is -2. Remember  that the sum of all the oxidation numbers in a compound must be zero.

The oxidation number of atoms in a diatomic molecule is zero hence in H2, H is zero.

We already know the oxidation states of oxygen and hydrogen in CH3OH to be -2 and +1 respectively. Carbon is;

x + 4(1) + (-2) = 0

x + 2 =0

x = -2

Hence in CH3OH, carbon has an oxidation state of -2.