Rate Equations & Arrhenius Flashcards
How do you find the individual order of something eg A
Look where A changes and the other things stay the same. Then compare A with rate
What’s the units for rate
Moldm^-3 s^-1
What’s the units for [A] eg
Moldm^-3
How do you know what species is the catalyst
it will be in the rate equation but not the overall equation
What is 0 order
No effect on ROR
What is 1st order
The same as ROR
What is 2nd order
The ROR is the [conc] squared ^2
How does temperature effect the rate constant (K)
As temperature increases the rate constant increases
Define the rate constant (k)
a number that connects the concentration of reactants in a reaction to the rate of that reaction
Define order of reaction
the power to which the concentration of that reactant is raised in the rate equation
How do you work out activation energy (Ea) in the Arrhenius equation
- RT(In A - In K)
- Then divide by 1000
How do you work out T in the Arrhenius equation
Activation energy/ R(In A - In k)
In the Arrhenius equation what units must activation energy be in
Joules. So if in kJ then multiply by 1000 to get in J
What will the units of A (Arrhenius constant) be the same as
The units of the rate constant
How do you work out the Arrhenius constant
K divided by e to the power of (-Ea/RT)
How would you know if iodine has all reacted
It would go from brown to colorless
How do you work out the rate equation from 2 or more reaction mechanisms
rate equation for a reaction includes all reactants which appear before and during the slowest step (rate determining step) in the mechanism
Intermediates are ruled out
How could you use a graph to work out Ea using R= 8.31
- Work out gradient from graph
- write down Gradient = -Ea/8.31
- Ea = 8.31 x gradient
- Divide by 1000
In what circumstance can the order of a reaction with respect or something be ignored?
- if there is a much larger amount of that than the other reactants
- the conc of it will stay almost constant
How would you know from a graph that a reaction is zero order?
- if it is a straight line
- Say the gradient is constant
- So the rate of reaction does not change as the reactant is used up
