Understanding Oxidizing Agents in 2CuO + C

[Drakkith]

Homework Statement

Which substance is the oxidizing agent in this reaction? 2CuO + C = 2Cu + CO₂

Homework Equations

2CuO + C = 2Cu + CO₂

The Attempt at a Solution

According to the online program I'm using for homework, CuO is the oxidizing agent, but I don't understand why. The oxidizing agent is the substance that gained electrons. Cu had an oxidation state of +2 prior to the reaction, and ends up gaining electrons to form neutral Cu. Each oxygen had an oxidation state of -2 prior to the reaction and ends up with -2 after the reaction. Carbon has an oxidation state of zero prior to the reaction and ends up with +4 after the reaction since it is reduced.

So 4 electrons are taken from carbon and given to 2 copper atoms. Shouldn't Cu be the oxidizing agent here? CuO doesn't even exist after the reaction, so how can it have gained electrons?

 

[Bystander]

All you want to look at is the reactant, no deeper details such as which metal oxide you're using to oxidize C, or the specific mechanism. Sorting "spectators" like K⁺ from chemistries of aqueous solutions can be arbitrary, and sorting oxidizer, oxidizing agent, can be equally arbitrary, but the reaction as written involves mixing two black solids and getting a bright metal and a gas as products, one reactant was oxidized, and one reactant was reduced. You can also look at it from the point of view that CuO is a way of identifying a specific oxidized copper compound to use in the reaction reducing copper.

 

[Drakkith]

So you're saying that since CuO is a reactant, you can't separate the Cu out of it and say that Cu was the oxidizing agent?

 

[Bystander]

Correct.

 

[Drakkith]

Thanks Bystander.

 

[Bystander]

Anytime. Chemistry can be "arbitrary" at times.

 

[Drakkith]

Eh. It's the memorization that's killing me.

 

[Bystander]

Been there --- enough rote memory will eventually reach a critical mass in which "contexts" will begin to take shape, and you'll be able to start memorizing exceptions to general rules rather than everything that's presented.