Video: EC17-18-S1-Q22

When iron (II) oxalate is heated in air, iron (III) oxide can be produced. Why does this happen?

02:08

Video Transcript

When iron two oxalate is heated in air, iron three oxide can be produced. Why does this happen?

Before we consider the chemical processes here, let’s have a review of what iron two oxalate is. This is the structure of the oxalate anion. It’s otherwise known as ethanedioate. And this is the structure of iron two oxalate. Now, let’s consider what happens when heating iron two oxalate in the absence of air. Now, this motif O C O should look familiar. Upon heating, it’s highly likely to form carbon dioxide and escape as a gas. Now, it’s not possible for both ends of the oxalate element to leave a CO₂. That would leave the iron two cation all on its own, which would not be very stable. Instead, heating the oxalate anion forms one carbon dioxide molecule and one carbon monoxide molecule, leaving behind iron two oxide. So there we have the complete equation.

So the next thing we have to consider is what happens to iron two oxide in the presence of air, when heated. Well, iron two oxide is prone to oxidation by oxygen. So when heated in air, iron two oxide forms iron three oxide. And here’s the balanced equation. We now have all the information needed to write the answer. When iron two oxalate is heated in air, iron three oxide can be produced because when iron two oxalate is heated in air, it first decomposes to iron two oxide. Iron two oxide is easily oxidized in air, forming iron three oxide. Alternatively, you could’ve just drawn the chemical equations for the processes involved.

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