Chapter 13 Chemical
Equilibrium
13.1 Rates of Reactions
Copyright © 2008 by Pearson Education, Inc.
Publishing as Benjamin Cummings
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Collision Theory of Reactions
For a chemical reaction to occur
• Collisions must have sufficient energy to break
the bonds in the reactants.
• Molecules must collide with the proper
orientation.
• Bonds between atoms in the reactants(N2 and
O2) must break and new bonds (NO) form.
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Copyright © 2008 by Pearson Education, Inc.
Publishing as Benjamin Cummings
Collision Theory of Reactions
A chemical reaction does not take place if the
• Collisions between molecules do not have
sufficient energy to break the bonds in the
reactants.
• Molecules are not properly aligned.
N2
3
O2
N2
O2
Activation Energy
Activation energy
• Is the minimum
energy needed
for a reaction to
take place.
• Must be
provided during
collision for
reactants to form
products.
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Copyright © 2008 by Pearson Education, Inc.
Publishing as Benjamin Cummings
Reaction Rate and
Temperature
Reaction rate
• Is the speed at which reactant is used up.
• Is the speed at which product forms.
• Increases when temperature rises because
reacting molecules move faster providing
more colliding molecules with energy of
activation.
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Reaction Rate and
Concentration
Reaction rate
• Is affected by the
concentration of the
reactants.
• Is increased by
adding more
reactants, which
increases the
number of collisions.
Copyright © 2008 by Pearson Education, Inc.
Publishing as Benjamin Cummings
6
Reaction Rate and
Surface Area
Reaction rate
• Is affected by the surface area of solid reactants.
• Is increased by increasing the surface area, which
exposes the solid reactant to more collisions with
the liquid or gas reactant.
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Copyright © 2008 by Pearson Education, Inc.
Publishing as Benjamin Cummings
Reaction Rate and Catalysts
A catalyst
• Speeds up the
rate of a
reaction.
• Lowers the
energy of
activation.
• Is not used up
during the
reaction.
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Copyright © 2008 by Pearson Education, Inc.
Publishing as Benjamin Cummings
Summary of Factors and
Reaction Rate
Table 13.1
Copyright © 2008 by Pearson Education, Inc.
Publishing as Benjamin Cummings
9
Learning Check
State the effect of each on the rate of reaction as:
1) increases
2) decreases
3) no change
A. Increasing the temperature.
B. Removing some of the reactants.
C. Adding a catalyst.
D. Placing the reaction flask in ice.
E. Increasing the concentration of one of the
reactants.
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Solution
State the effect of each on the rate of reaction as:
1) increases 2) decreases 3) no change
1 A. Increasing the temperature.
2 B. Removing some of the reactants.
1 C. Adding a catalyst.
2 D. Placing the reaction flask in ice.
1 E. Increasing the concentration of one of the
reactants.
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Learning Check
Indicate the effect of each on the rate of the
reaction as 1) increases 2) decreases 3) none:
2CO(g) + O2(g)
2CO2 (g)
A.
B.
C.
D.
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Raising the temperature
Adding O2
Adding a catalyst
Lowering the temperature
Solution
Indicate the effect of each on the rate of the
reaction as 1) increases 2) decreases 3) none:
2CO(g) + O2(g)
2CO2 (g)
A.
B.
C.
D.
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(1)
(1)
(1)
(2)
Raising the temperature
Adding O2
Adding a catalyst
Lowering the temperature