3.1.9: Rate equations Flashcards
(12 cards)
What is the order of a reaction (n)?
the power in which the concentration of the reactant is raised in a rate equation
What is the overall order of a reaction?
the total sum of all the powers of the reactants or products
- must be found experimentally, can’t be found by looking at the equation
- therefore, rate equation only found by experiment
What are the different orders of a reaction?
- zero order (n=0)- the reaction rate proportional to [A]^0=1, rate not affected by change in [A]
- first order (n=1)- the reaction rate is proportional to [A]
- second order (n=1)- the reaction rate is proportional to [A]^2
What is the rate equation?
rate= k[A]m[B]^n
- k= rate constant
How do you find the rate equation?
- overall order= (m+n) powers
- m+n must be found experimentally, can’t be found by looking at the equation
- catalyst can appear in rate equation
- k= rate constant, different for each reaction
What is k affected by?
- only temperature and catalyst
- units of k depend on roder of reaction
What is the rate determining step?
the slowest step in the reaction mechanism
What’s found in the rate determining step?
- catalyst and reactant
- catalyst- used to speed up RDS (as slowest) by lowering Ea
- order of reactant- how many nol in RDS
- intermediate reacts quickly, never reactant in RDS
- needs to cancel out to make stochiometric equation
What is Arrhenius equation?
k = Ae ^ (-Ea/RT)
or
lnk = lnA - (Ea/RT)
How is Arrhenius equation modelled on a graph?
- y intercept- lnA
- y= lnk
- x= 1/T
- m=-Ea/R
What do concentation-time graphs show about order?
- zero order- straight line downwards
- first order- curve line downwards
- second order- curvier line downwards
What do rate-concentration graphs show about order?
- zero order- straight line no gradient
- first order- straight line upwards
- second order- exponential graph
