The high- and low-pressure limits relate to the different behaviour of a unimolecular reaction; specifically to the rate of reaction at these extremes at a constant temperature. At infinitely high-pressure the reaction is first order in reactant and at low pressures the reaction becomes second order … first order in reactant and first order in the bath gas. It becomes more difficult to observe the hi-pressure limit experimentally at high temperatures and with small molecules.
Most university level physical chemistry texts describe this situation and those are better places to start your enquiries.
J. M. Simmie//NUIG//Ireland
>Sent to CCL by: "bonoit bonoit" [bonoit_10[-]yahoo.fr] Dear CCLers,
>I would like to enquire about the meaning of high-pressure limit and low-pressure limit and what are their influence on the rate >of a given reaction. I mean why some products form in the high-pressure limit and other low-pressure limit?
>What is the relation of these two pressure limits with temperature?