Draw a chemical equation to represent the redox reaction that ...

Question

Draw a chemical equation to represent the redox reaction that occurs when methane (CH₄) burns in the presence of oxygen (O₂). Identify the reactant that is reduced and the reactant that is oxidized. Of the four molecules that should be in your equation, point out the one that has bonds with the highest potential energy.

Accepted Answer

Hi everyone. Let's look at our next problem. It says study carefully the following metabolic reaction. We have CH four plus 02 going to C. 02 plus H 20. Methane and oxygen going to carbon dioxide and water. And then it says identify the incorrect statement regarding the above reaction. So, remember, we'll be looking for the false statement here. Well, anytime we have a molecule combining with elemental oxygen to see that oxygen combining with another molecule in the products that's a combustion reaction and that is a type of redox reaction. So let's keep that in mind. So when we look at our answer choices, Choice a says methane is oxidized while oxygen is reduced but we know we have a redox reaction, oxygen 02 is a powerful oxidizing agent. That's where the very name oxidizing comes from. So oxygen is pretty much always going to be reduced. And indeed we can sort of confirm that in the if we kind of rewrite our reaction down here in a little more space. If we look at the oxidation states of the different atoms here, uh in oh two pure oxygen, the oxidation state of oxygen will be zero because it's always zero if you just have the element by itself and when we look over water, we know that water, hydrogen is pretty much always plus one. So the hydrogen Will be in an oxidation state of Plus one. Whereas the oxygen then to balance it, we've got two, hydrogen is an oxidation state of minus two and of course that is the oxidation state most common to oxygen likes being in that state and carbon dioxide. Well, we'll look at the oxygen first again, most likely to be in that -2 state. There's two of them. So the carbon and carbon dioxide must have an oxidation state of plus four to give it a neutral charge overall. So let's look at our methane. Well, with methane, we've gotta sign the hydrogen first. So we're going to sign it an oxidation state of plus one, there's four of them. So the carbon must have an oxidation state of -4. So our carbon has gone from an oxidation state of -4 to plus four. It has increased an oxidation state. It has been oxidize. And again, that makes sense because we would expect the oxygen to be reduced. So Choice A is true and therefore not our answer. Since we're looking for an incorrect statement, Choice B says methane contains the highest amount of potential energy while methane is a very high energy molecule with its four ch bonds. So that is true and therefore not our answer. Choice C says it is an incomplete oxidation of methane molecule. Well, that is incorrect. This is a combustion reaction. It is the complete oxidation or burning of methane. It's all been converted into CO two so that is false. It is a complete oxidation and therefore we can expect that choice C is going to be our correct answer. Finally, just to be thorough, we'll look at Choice D, Choice D says the overall reaction is a redox one. Well, as we saw in the beginning, this is a combustion reaction. We have, um, elements changing their oxidation states, and therefore, yes, this is a redox reaction, so Choice D. Cannot be our correct answer. So the incorrect statement regarding this above combustion reaction is Choice C. It is an incomplete oxidation of methane molecule. Thanks for watching See you in the next video.

Key Concepts

Redox Reactions

Combustion of Methane

Potential Energy in Chemical Bonds

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