Activation energy - EduEx

Additional resources

The Coldest Reaction

16.2 Activation energy

Understanding

The Arrhenius equation uses the temperature dependence of the rate constant to determine the activation energy.

Guidance
Use energy level diagrams to illustrate multi-step reactions showing the RDS in the diagram.

A graph of 1/T against lnk is a linear plot with gradient –Ea/R and intercept InA.
The frequency factor (or pre-exponential factor) (A) takes into account the frequency of collisions with proper orientations.

Applications and skills

● Analysing graphical representation of the Arrhenius equation in its linear form k
−E
RT
ln = a +lnA .
● Using the Arrhenius equation k Ae
E
RT
a
=
−
.
Guidance
● Consider various data sources in using the linear expression k
RT
ln = +lnA
−Ea .
● The expression
k
R
ln =
E1 a
k2
1
T2
1
T1
( − ) is given in the data booklet.
● Describing the relationships between temperature and rate constant; frequency factor and
complexity of molecules colliding.
● Determining and evaluating values of activation energy and frequency factors from data.

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