In C2H4(g) + 3O2(g) giving 2CO2(g) + 2H2O(l), what happens to carbon?

1. In C2H4 each hydrogen is +1, so four hydrogen atoms give +4. 2. The molecule is neutral, so the two carbon atoms together must be -4, that is -2 each. 3. In CO2 oxygen is -2, so two oxygen atoms give -4 and carbon must be +4. 4. Carbon therefore moves from -2 up to +4, an increase, which is oxidation. 5. Oxygen moves from 0 in O2 down to -2, a decrease, so oxygen is reduced. 6. That makes C2H4 the reducing agent, or fuel, and O2 the oxidizing agent. 7. Reading the change backwards is the common trap, since the fuel is always the one oxidized. _Source: OpenStax Chemistry (CC BY 4.0), Ch 4 "Stoichiometry of Chemical Reactions", section 4.2 Classifying Chemical Reactions_