[netgeek]

Hello,

     I am currently studying rates of reaction. I have in my notes that a catalyst and the nature of a reactant affect the number of effective collisions between particles. I am not sure though how they do this? Can anyone please explain to me how a catalyst and the nature of a reactant affect the fraction of effective collisons???

Thank you.

[Demotivator]

Well, most of the time  molecules bounce off one another and nothing happens because a couple of things need to occur; the collision is at the right spot and the thermodynamics of bond breaking/making are favorable.
The nature of the reactant has an effect because if the reactant has a complicated or bulky structure that makes it difficult for another molecule to hit it at the right spot, the effective collisions will be lower. Likewise, if the reactant has strong bonds that won't easily break.

A catalyst typically helps increase the effective collisions by weakening the bonds of the reactant (by making temporary bonds with the reactant) and thus allowing another molecule to bond with the reactant, replacing the catalyst.  

[netgeek]

Thank you very much!  

This is making sense now!