Chemistry 12—Unit 3-Reaction Kinetics--Notes
Energy Diagrams Practice
Ea,  and bond strengths for forward and reverse reactions
ACTIVATED
COMPLEX
100
90
80
POTENTIAL
ENERGY
70
60
Ea – Energy needed
for Reactants to
form the Activated
Complex
50
40
REACTANTS
- Energy Difference between
Reactants and Products. (In this
case  is negative so Rx. is
Exothermic
30
20
PRODUCTS
10
Progress of Reaction
Try this question:
ACTIVATED
COMPLEX
2 00
18 0
16 0
14 0
12 0
10 0
REACTANTS
80
Forward Reaction
60
40
PRODUCTS
20
Progress of Reaction
Using the graph above, find:
Ea (forward rx.) = _________kJ
 (forward rx. ) = _________kJ
This forward reaction is ______thermic
Chemistry 12—Unit 1-Reaction Kinetics—Notes
Page 1 of 6 pages
Chemistry 12—Unit 3-Reaction Kinetics--Notes
-Considering reverse rx.
ACTIVATED
COMPLEX
2 00
18 0
POTENTIAL
ENERGY
16 0
14 0
12 0
10 0
Ea (reverse rx.)
REACTANTS
80
60
reverse rx.)
40
Reverse Reaction
PRODUCTS
20
Progress of Reaction
 (reverse rx. ) = _________kJ
Ea (reverse rx.) = _________kJ
This reverse reaction is ______thermic
Given the following Potential Energy Diagram for the Reaction:
A2 + B2
50

2AB
A2B2
45
POTENTIAL
ENERGY
40
35
30
25
A2 + B2
20
15
10
2 AB
5
Progress of Reaction
a)
Ea (forward) =
kJ
b)
Energy needed to break bonds in A2 & B2
A-A B-B
Chemistry 12—Unit 1-Reaction Kinetics—Notes
kJ
Page 2 of 6 pages
Chemistry 12—Unit 3-Reaction Kinetics--Notes
c)
Ea (reverse) =
kJ
d)
Energy needed to break bonds in AB (A-B)
kJ
e)
Which has the stronger bonds A2 & B2 or 2AB?
f)
On a PE diagram, species with stronger bonds (more stable) are
(low/high)__________________er on the graph
g)
Which set of species (A2 & B2, A2B2, or 2AB) have the weakest bonds?
. This species is the most
stable. It is called the
__________________________ ______________________________
h)
Which set of species has the highest PE?_________________________
i)
Which set of species has the highest KE?_________________________
j)
Draw a graph of KE vs. reaction proceeds for the same forward rx.
KINETIC
ENERGY
Progress of Reaction
Chemistry 12—Unit 1-Reaction Kinetics—Notes
Page 3 of 6 pages
Chemistry 12—Unit 3-Reaction Kinetics--Notes
Energy Diagrams Practice - ANSWERS
Ea,  and bond strengths for forward and reverse reactions
ACTIVATED
COMPLEX
100
90
80
POTENTIAL
ENERGY
70
60
Ea – Energy needed
for Reactants to
form the Activated
Complex
50
40
REACTANTS
- Energy Difference between
Reactants and Products. (In this
case  is negative so Rx. is
Exothermic
30
20
PRODUCTS
10
Progress of Reaction
Try this question:
ACTIVATED
COMPLEX
2 00
18 0
16 0
14 0
12 0
10 0
REACTANTS
80
Forward Reaction
60
40
PRODUCTS
20
Progress of Reaction
Using the graph above, find:
Ea (forward rx.) = _70_kJ
 (forward rx. ) = ___-80_kJ
This forward reaction is __exo_thermic
Chemistry 12—Unit 1-Reaction Kinetics—Notes
Page 4 of 6 pages
Chemistry 12—Unit 3-Reaction Kinetics--Notes
-Considering reverse rx.
ACTIVATED
COMPLEX
2 00
18 0
POTENTIAL
ENERGY
16 0
14 0
12 0
10 0
Ea (reverse rx.)
REACTANTS
80
60
reverse rx.)
40
Reverse Reaction
PRODUCTS
20
Progress of Reaction
 (reverse rx. ) = __+80__kJ
Ea (reverse rx.) = __150__kJ
This reverse reaction is __endo_thermic
Given the following Potential Energy Diagram for the Reaction:
A2 + B2

50
2AB
A2B2
45
POTENTIAL
ENERGY
40
35
30
25
A2 + B2
20
15
10
2 AB
5
Progress of Reaction
a)
Ea (forward) =
20
kJ
b)
Energy needed to break bonds in A2 & B2
A-A B-B
Chemistry 12—Unit 1-Reaction Kinetics—Notes
20
kJ
Page 5 of 6 pages
Chemistry 12—Unit 3-Reaction Kinetics--Notes
c)
Ea (reverse) = 40
kJ
d)
Energy needed to break bonds in AB (A-B)
40
kJ
e)
Which has the stronger bonds A2 & B2 or 2AB?
f)
On a PE diagram, species with stronger bonds (more stable) are
(low/high)_____lower____er on the graph
g)
Which set of species (A2 & B2, A2B2, or 2AB) have the weakest bonds?
A2B2
. This species is the most
un
stable. It is called the
_________activated_____ _____complex___________
h)
Which set of species has the highest PE?_____ A2B2__________
i)
Which set of species has the highest KE?____ 2AB___________
j)
Draw a graph of KE vs. reaction proceeds for the same forward rx.
KINETIC
ENERGY
Basically, this graph
should be the mirror
image of the PE graph
since as PE increases,
KE decreases and vice
versa.
Progress of Reaction
Chemistry 12—Unit 1-Reaction Kinetics—Notes
Page 6 of 6 pages