Rate Determining Step

Question 1

What is the rate determining step?

Answer 1

The slowest step in a multi step reaction which determines the rate of reaction

Question 2

What must appear in the rate determining step?

Answer 2

All the reactants in the rate equation
Or substances derived from it (eg shows up before the rate determining step)
Catalysts

Question 3

What must appear in the rate determining step?

Answer 3

All the reactants in the rate equation
Or substances derived from it (eg shows up before the rate determining step)

Question 4

Why do certain reactants appear in the rate determining step?

Answer 4

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)

Question 5

What can be done with rate determine step?

Answer 5

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

Question 6

How to find rate equation from multi step reactions?

Answer 6

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

Question 7

How to find what the rate determining step is from the rate equation?

Answer 7

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

Question 8

Choosing mechanism from rate determining step

Answer 8

Choose the Mechanism which has only the reactant in the rate equation in the rate determining step

Question 9

What to remember in writing mechanisms

Answer 9

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

Question 10

Suggesting and writing a mechanism

Answer 10

Having to make a mechanism for a reaction when given the rate equation

Question 11

When writing a mechanism…

Answer 11

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

Question 12

What does the number of moles of reactants in the rate determining step show?

Answer 12

The order of those reactants

Question 13

If the reaction has a zero order reactant…

Answer 13

Then there must be multiple stages in the mechanism (as well as the rate determining step) because the zero order reactant will be involved but not in the rate determining step