: How do catalysts work?

Question

1) why arent they consumed in the reaction ( can you explain step by step how it influences the reaction?)
2) is it energy related?

In: 4

Answer 1

Well, consider a concrete example: destruction of ozone by chlorine. The reactions are:

* Cl + O3 => ClO + O2
* ClO + O3 => Cl + O2 + O2

That is, chlorine (Cl) reacts with ozone (O3) to produce chlorine monoxide (ClO) and oxygen (O2). The chlorine *is* consumed in the reaction. But then a second reaction occurs: the chlorine monoxide reacts with more ozone to produce chlorine and more oxygen. So then we have chlorine again, which is the same chemical we started with. So when we consider the sequence as a whole (which amounts to Cl + 2O3 => Cl + 3O2), the chlorine was not consumed.

And, I mean, yes, you can talk about it in terms of energy. O3 is lower energy than O2 + O, so the ozone molecules are somewhat stable on their own. But Cl + O3 is higher energy than ClO + O2, so chlorine can break ozone molecules. And then ClO + O3 is also higher energy than Cl + 2O2, so chlorine monoxide can *also* break ozone molecules.