Rate Determining Step Flashcards
What is the rate determining step?
The slowest step in a multi step reaction which determines the rate of reaction
What must appear in the rate determining step?
All the reactants in the rate equation
Or substances derived from it (eg shows up before the rate determining step)
Catalysts
What must appear in the rate determining step?
All the reactants in the rate equation
Or substances derived from it (eg shows up before the rate determining step)
Why do certain reactants appear in the rate determining step?
Because they can be first/second order so will have an effect on rate in some way thus must be in rate determining step
(0 order has no effect on rate)
What can be done with rate determine step?
Finding the rate equation from multi step reaction
Finding rate determining step from rate equation and steps
Finding mechanism from what the rate determining step is
How to find rate equation from multi step reactions?
Any reactant in the rate determining step must be in the rate equation (large number in front determines order)
Any reactants that form this reactant eg if this reactant in rate determining step is an intermediate/catalyst
How to find what the rate determining step is from the rate equation?
Find the step which has accounted for all the reactants in the rate equation
Mark off the reactants till you have accounted for all that show in rate equation = rate determining step
Choosing mechanism from rate determining step
Choose the Mechanism which has only the reactant in the rate equation in the rate determining step
What to remember in writing mechanisms
Those in the rate equation must be in the rate determining step
Based on the orders of the equation, shows how many molecules are in the rate determining step
Those reactants not in rate determining step MUST appear after it
Catalysts present in rate determining step must be reformed by end
Cancelling out mechanisms on either side = overall equation
Suggesting and writing a mechanism
Having to make a mechanism for a reaction when given the rate equation
When writing a mechanism…
Start with the reactant in the rate determining step
Form one of the products shown in the overall equation (remaining atoms make another product)
Any products made in first reaction not in the overall equation are intermediates
Intermediates must be used up
All reactants must be accounted for in all stages
Products must add up to final product