Transcript The Arrhenius Equation

The Arrhenius Equation
• Collision Theory: A bimolecular reaction
occurs when two correctly oriented
molecules collide with sufficient energy.
• Activation Energy (Ea): The potential
energy barrier that must be surmounted
before reactants can be converted to
products.
The Arrhenius Equation
The Arrhenius Equation
The Arrhenius Equation
• This relationship is summarized by the
Arrhenius equation.
E

- a RT


k = Ae
• Taking logs and rearranging, we get:
 Ea 1 
ln k = ln A
+

 
R T
The Arrhenius Equation
Temp
k
(°C) (M-1 s-1)
283 3.52e-7
356
393
3.02e5
2.19e-4
427
1.16e-3
508
3.95e-2
The Arrhenius Equation
The
The second-order
second-order rate
rate constant
constant for
for the
the
decomposition
decomposition of
of nitrous
nitrous oxide
oxide (N
(N22O)
O) into
into nitrogen
nitrogen
molecule
molecule and
and oxygen
oxygen atom
atom has
has been
been measured
measured at
at
different
different temperatures:
temperatures:
Determine
Determine graphically
graphically
the
the activation
activation energy
energy
for
for the
the reaction.
reaction.
kk (M
(M-1-1ss-1-1))
1.87x10
1.87x10-3-3
0.0113
0.0113
0.0569
0.0569
0.244
0.244
tt (°C)
(°C)
600
600
650
650
700
700
750
750
The Arrhenius Equation
• A simpler way to use this is by comparing the rate
constant at just two temperatures:
Ea  1 1 
k2
ln =  - 
k1
R T2 T1
• If the rate of a reaction doubles by increasing the
temperature by 10°C from 298.2 K to 308.2 K,
what is the activation energy of the reaction?
