Kinetics (Year 2) Flashcards
Define the term rate of reaction
Change in concn per unit of time
How do you calculate rate of reaction?
Rate of reaction = change in concn / change in time
What affects the value of the rate constant?
Temperature
Give an example of a rate expression
Rate = k [A]a [B]b
k = constant
[A] and [B] = species concn
a and b = order of reaction
Define the term order of reaction
The power to which a species concn is raised in the rate equation
What are the units for each component in a rate equation?
Rate = mol dm-3 s-1
Concn = mol dm-3
k = dependent on other units (sub them in then cancel out)
Explain a rate concn graph for a zero order reactant
Rate remains the same as concn increas
Explain a rate concn graph for a first order reactant
Both rate and concn proportionally increase
Explain a rate concn graph for a second order reactant
As concn increases, rate increases exponentially
What is the effect of 10K on the rate of reaction?
Doubles rate of reaction
What is the half life of a first order reactant?
Half life is constant
What is the Arrhenius equation?
-Ea / RT
k = A e
k = rate constant
A = pre-exponential factor
e = mathematical quantity
R = gas constant
Ea = activation energy
T = temperature
How can you convert the Arrhenius equation to plot on a graph?
ln k = -Ea / RT + ln A
What is the rate determining step?
The slowest step in a reaction mechanism
Determines the overall rate of reaction
How does the rate determining step affect the rate expression?
Species in the R.D.S. appear in the rate expression
Species NOT in the R.D.S. do NOT appear in the rate expression
