Chapter 18 Outline
Reaction Rates and Equilibrium
 The rate of a chemical reaction depends upon
_________________________________________________
_________________________________________________
______________________________________.
Section 18.1 – Rate of Reaction
 A
is a measure of the
change that occurs within an interval of
 In chemistry, the
the
amount of
of any
.
of chemical change or
is usually expressed as the
changing per unit of time.
 According to
, particles can
react to form products when they
with
one another, provided that the colliding particles
have enough
.
 The
that colliding
particles must have in order to react is called the
________________________.
 An
is an unstable
arrangement of atoms that forms _________________
at the
of the activation-energy barrier.
 The activated complex
is sometimes called the
______________________.
 Usually, ____________ the temperature
_________________ reactions.
 Increasing the
the frequency of
of particles that have enough
over the
 The
affects the
increases both
and the number
to slip
.
of particles in a given volume
at which reactions occur.
 More
increase the __________________
which increase the number of _________________
leading to a higher reaction rate.
 The
the reaction rate.
 The
area.
the particle, the
 An increase in
amount of the reactant
 A
without being
of a reactant affects
surface
increases the
for reaction.
increases the rate of reaction
during the reaction.

along a
Section 18.2 – Equilibrium
permit the reaction to proceed
.
 Since a catalyst is
during a
reaction, it does not appear as a _________________
___________________.
 Instead, the catalyst is written
yield
.

the
in your digestive tract act as
_______________ for breaking down
 It takes your body a
 When the
reactions are
reached
.
to digest proteins.
 Without the enzymes, it would take _______________
for you to digest your food.
Section 18.1 Assessment
1. How is the rate of a chemical reaction expressed?
2. What are four factors that affect the rate of a
chemical reaction?
3. Does every collision between reaction particles
lead to products? Explain.
4. Why does refrigerated food stay fresh longer than
room temperature food?
 A
is one in which the
conversion of reactants to products and the
conversion of products to reactants occur
______________________.
of the forward and reverse
, the reaction has
.
 At chemical equilibrium, no
in the
components of the system.
occurs
of the
 The relative
of the
reactants and products at equilibrium constitute
the
of a reaction.
 The
indicates
whether the reactants or products are
____________ in a reversible reaction.

states that if a
____________ is applied to a system in
___________________, the system changes in a
way that
the stress.
 Stresses that upset the equilibrium include
_______________________________________________
_______________________________________________
______________________________________________.
 Changing the
of any
reactant or product at equilibrium _____________
the equilibrium.
 The system adjusts to
of the change by
the effects
the equilibrium.
 Increasing the
causes the
________________________ to shift to the direction
that
.
 Think of
the
as a reactant or product in
.
 A change in
only affects
____________ equilibria that have an unequal
number of
of reactants and products.
Sample Problem
 What effect do each of the following changes
have on the equilibrium position for this following
reaction?
PCl5(g) + heat  PCl3(g) + Cl2(g)
a. Addition of Cl2
b. Increase in pressure
c. Removal of heat
d. Removal of PCl3 as it is formed
 The
is the ratio of
the
concentration to _____________
concentration at equilibrium, with each
concentration raised to a
equal to
the number of
of that substance in
the
chemical equation.
 Generic Reaction:
 Equilibrium Constant:
Keq =
 Keq > 1,
 Keq < 1,
favored at equilibrium
favored at equilibrium
Sample Problem
 A liter of a gas mixture at equilibrium contains
0.0045mol or N2O4 and 0.030mol of NO2.
Calculate Keq.
N2O4(g)  2NO2(g)
Practice Problem
 At equilibrium, a 1L flask contains 0.15 mol H2,
0.25 mol N2, and 0.10 mol NH3. Calculate Keq for
the reaction.
N2 + 3H2  2NH3
Section 18.2 Assessment
1. How do the amounts of reactants and products
change after a reaction has reached chemical
equilibrium?
2. What are three stresses that can upset the
equilibrium of a chemical system?
3. What does the value of the equilibrium constant
tell you about the amounts of reactants and
products present at equilibrium?
4. How can a balanced chemical equation be
used to write an equilibrium-constant
expression?
5. Can a pressure change shift the equilibrium
position in every reversible reaction? Explain.
6. Using the following equilibrium constants,
determine which reactions would favor the
products.
a. 1 x 102
b. 0.003
c. 3.5