Answer:
H2
Step-by-step explanation:
CO2 + H2 → CO + H2O
↓ (-2). 0. (+2 )(-2). (+1)(-2)
↓ ·2 (+2)
+4 (-4)
Write down the oxidation number under each element, each molecule should equal 0 unless there is a charge shown.
Oxygen, always has an oxidation number of -2 unless in a peroxide.
Hydrogen, is -1 with metals,+1 with non-metals. Hydrogen loves non-metals!
H2 is zero because any standalone element has an oxidation number of zero
What is being oxidized? Whatever is being oxidized, loses electrons and becomes more positive, it will be a whole molecule, not just an element. In this case, the H in H2 goes from 0 to (+1) so it is the oxidized molecule.