Negative orders in reactions

[smhjn17]

I know negative order wrt a reactant signifies an inverse effect on the rate...

However can i know an example of such a situation?

Moreover products cannot be included in the rate bcos they dont affect the rate so wat bt this reaction:

2O3--> 3O2 rate= k[O3]^2 [O2]^-1

Firstly, on what grounds is this product O2 included in rate law eq.

Secondly , the rate is actually undefined instead of 2-1=1

Plz explain...

[hypervalent_iodine]

1. You gave yourself an example with the ozone reaction.

 

2. Who says products don't affect reaction rate? They can and do and where this is the case, they are included in equations defining the reaction rate.

 

3. The order of the reaction is really something that you determine experimentally. Having a negative order indicates that the mechanism is quite complex and you can't simply add the numbers together as you suggest, hence why it is undefined.

[smhjn17]

I want to know an example in which a reactant has a negative order

[studiot]

Here is an extract from a university level text that has many examples to look at.

 

Chemical Kinetics and Reaction Mechanisms by Wilkinson.

 

 

 

 

[smhjn17]

Thnk u so much..really helpful...

[studiot]

I hope you noticed he makes very clear that all the exponents should be determined experimentally.

 

I meant to say this before.

Edited June 19, 2015 by studiot

[mississippichem]

I hope you noticed he makes very clear that all the exponents should be determined experimentally.

 

I meant to say this before.

Yes! It is a common source of confusion for people to draw up a mechanism and try to write down reactant orders.

 

Kinetics on paper are easy to understand and neat. Kinetics in real solutions are always messy.