Question

What are the oxidation numbers of the atoms in this reaction?

Check all that apply.

CH4(g) + 2O2(g) → CO2(g) + 2H2O(g)

-4 for C in CH4

+4 for C in CO2

-2 for O in all substances

+1 for H in both CH4 and H2O

+4 for O in H2O

Answer 1

Correct choices:

- -4 for C in CH4 (H is +1, so C + 4(+1) = 0 → C = −4)
- +4 for C in CO2 (each O is −2, so C + 2(−2) = 0 → C = +4)
- +1 for H in both CH4 and H2O (H bonded to nonmetals is +1)

Incorrect choices:

- −2 for O in all substances — O is 0 in O2 (elemental), −2 in CO2 and H2O.
- +4 for O in H2O — O is −2 in H2O.