Download The Arrhenius Equation

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Date: ___________
The Arrhenius Equation
Unit: Kinetics
Skills:

calculate values for Ea from rate law and temperature data
Recall that the rate of a chemical reaction increases as the activation
energy decreases. In 1889, the Swedish chemist Svante Arrhenius
determined that the rate constant k obeys the equation:
k  Ae
E
 RTa
where A is a constant, Ea is the activation energy, R is the gas constant,
and T is the temperature (in Kelvin).
Use this space for additional notes.
Chemistry II
Copyright © 2010–2017 Mr. Bigler.
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The Arrhenius Equation
Taking the logarithm of both sides of the equation gives the Arrhenius
equation in logarithmic form:
ln k  ln A 
Ea
RT
Because A is a constant, so is ln A. Therefore, the Arrhenius equation is a
straight line plot in y = mx + b form:
y 
m x  b
ln k  
Ea  1 
   ln A
R T 
This means that if we graph ln k vs.
E
1
, the slope will be  a .
T
R
Multiplying the slope by the gas constant R gives the activation energy Ea
for the reaction.
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Chemistry II
Mr. Bigler
Page 2 of 3
Mark Important
The Arrhenius Equation
Points in Margin
If you have two values for k at two different temperatures, you can
calculate Ea as follows:
ln
k2
E 1
1
 a   
k1
R T2 T1 
The equation is usually given as:
ln
k2 E a  1
1

  
k1
R T1 T2 
Notice that we reversed the order of
negative sign in front of
Ea
.
R
Note also that if you use R  8.31
kJ
mol
J
mol K
1
1
&
in order to get rid of the
T1
T2
, then Ea comes out in
instead, you need to use R  8.31  10
3
kJ
mol K
J
mol
. If you want
.
Use this space for additional notes.
Chemistry II
Mr. Bigler
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