## Catalyst, Equation, and Rate Law

Arrhenius Equation: $\ln k = - \frac{E_{a}}{RT} + \ln A$

Ava Harvey 2B
Posts: 54
Joined: Fri Sep 29, 2017 7:04 am

### Catalyst, Equation, and Rate Law

I understand that a catalyst speeds up a reaction by providing an alternative pathway, however, I don't understand why it doesn't appear in the balanced equation for a reaction, yet it does appear in the rate law. If someone wouldn't mind explaining that to me, that would be great! Thanks so much!

Shawn Patel 1I
Posts: 54
Joined: Thu Jul 27, 2017 3:01 am

### Re: Catalyst, Equation, and Rate Law

Hey,
A catalyst is accounted for in the rate law because it speeds up the reaction. It isn't considered in a balanced chemical equation because it doesn't undergo any change, nor does it affect any of the reactants in anyway besides increasing the speed of the reaction.

LMendoza 2I
Posts: 41
Joined: Sat Jul 22, 2017 3:00 am

### Re: Catalyst, Equation, and Rate Law

Shawn Patel 1I wrote:Hey,
A catalyst is accounted for in the rate law because it speeds up the reaction. It isn't considered in a balanced chemical equation because it doesn't undergo any change, nor does it affect any of the reactants in anyway besides increasing the speed of the reaction.

So basically, does the catalyst not react or interact with the reactants at all?

Shawn Patel 1I
Posts: 54
Joined: Thu Jul 27, 2017 3:01 am

### Re: Catalyst, Equation, and Rate Law

The catalyst itself is not consumed during the reaction and so it does not interfere with the reactants turning into the products, aside from decreasing activation energy so that the process is sped up.

Harjas Sabharwal 1G
Posts: 42
Joined: Sat Jul 22, 2017 3:01 am

### Re: Catalyst, Equation, and Rate Law

The poster above did a good job explaining the concept, so here is an example using an enzyme. Enzymes bring their substrates together and then alter their formation to make them more likely to react and thus start the reaction. However, it would be horribly energy inefficient if a cell had to create a new enzyme every time it reacted. Hence, enzymes, and catalysts by extension are not used up in a reaction, and thus not included in the chemical equation.