Consider the following reaction
CO2(g) + H2(g) — COG) + H2011)
What is being oxidized?
carbon
carbon dioxide
oxygen
hydrogen
Dedio

H2

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.

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