Question #9d2da

1 Answer
Dec 15, 2014

What you are looking for is acetylen's combustion reaction, which can also be viewed as an oxidation-reduction reaction.

2C_2H_2 + 5O_2 -> 4CO_2 + 2H_2O

Let's assign oxidation numbers for all atoms involved in the reaction

2C_2^(-1)H_2^(+1) + 5O_2^(0) -> 4C^(+4)O_2^(-2) + 2H_2^(+1)O^(-2)

We can see that C's oxidation number goes from (-1) on the reactants' side, to (+4) on the products' side

C^(-1) -> C^(+4) + 5e^_ (for each individual C atom);

O's oxidation number went from (0) an the reactants' side, to (-2) for both products

O^0 + 2e^(-) -> O^(-2) (for each individual O atom);

The total number of electrons lost by C is 4 * 5e^(-) = 20e^-, while the total number of electrons gained by O is 8 * 2 e^(-) + 2 * 2e^(-) = 20e^(-) -> determined from the balanced REDOX reaction.

Therefore, C is being oxidized - acts as a reducing agent, while O is being reduced - acts as an oxidation agent.