General organic and biological chemistry structures off life 5th CH10 rates of reactions GOB structures 5th ed

Lecture Presentation

Chapter 10

Reaction Rates and Chemical
Equilibrium

Karen C. Timberlake

General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

© 2016 Pearson Education, Inc.


Chapter 4 Reaction Rates and Chemical Equilibrium

A neonatal nurse works with newborns that are
premature or have birth defects, cardiac
malformations, and surgical problems.

Most neonatal nurses care for infants from the time
of birth until the time they are discharged from the
hospital.

General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

© 2016 Pearson Education, Inc.

Chapter 10 Readiness

Key Math Skills

•
•

Solving Equations (1.4D)
Writing Numbers in Scientific Notation (1.4F)

Core Chemistry Skills

•
•
•

Using Significant Figures in Calculations (2.3)
Balancing a Chemical Equation (7.1)
Calculating Concentration (9.4)

General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

© 2016 Pearson Education, Inc.


10.1 Rates of Reactions

Reaction rates vary greatly for everyday
processes. A banana ripens in a few days,

silver tarnishes in a few months, while the
aging process of humans takes many years.

Learning Goal Describe how temperature, concentration, and catalysts affect the rate of a
reaction.
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

© 2016 Pearson Education, Inc.


Rates of Reaction

Reacting molecules must collide, have a minimum amount of energy, and have the proper orientation to form
products.

General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

© 2016 Pearson Education, Inc.


Activation Energy

•

Even when a collision has the proper orientation, there still must be sufficient energy to break the
bonds between the atoms of the reactants.

Three Conditions Required for a Reaction to Occur

1. Collision

The reactants must collide.

2. Orientation

The reactants must align properly to

3. Energy The collision must provide the energy

General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

break and form bonds.

of activation.

© 2016 Pearson Education, Inc.


Activation Energy

•

The activation energy is the minimum amount of energy required to break the bonds between atoms of
the reactants.

General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

© 2016 Pearson Education, Inc.


Rate of Reaction

The rate (or speed) of a reaction is determined by measuring the amount of

•
•

reactant used up in a certain period of time.
product formed in a certain period of time.

General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

© 2016 Pearson Education, Inc.


Factors That Affect the Rate of a Reaction

Reactions with low activation energies go faster than reactions with high activation
energies.

For any reaction, the rate is affected by

•
•
•

changes in temperature.
changes in reaction concentration.
adding a catalyst.

General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

© 2016 Pearson Education, Inc.


Rate of Reaction: Temperature

At higher temperatures the increase in kinetic energy of the reactant molecules

•
•
•

makes them move faster.
makes them collide more often.
makes them collide with more energy.

For every 10 °C increase in temperature, most reaction rates approximately double.

General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

© 2016 Pearson Education, Inc.

Rate of Reaction: Reactant Concentration

When there are more reacting
molecules, more collisions that
form products can occur, and the
reaction goes faster.

General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

© 2016 Pearson Education, Inc.


Rate of Reaction: Catalysts

•

Adding a catalyst speeds up the rate of the
reaction by providing an alternative pathway that
has a lower activation energy.

•

When activation energy is lowered, more
collisions provide sufficient energy for reactants to
form product.

•

During a reaction, a catalyst is not changed or

consumed.

General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

© 2016 Pearson Education, Inc.


Factors That Affect Reaction Rates

General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

© 2016 Pearson Education, Inc.


Study Check

Indicate the effect of each factor listed on the rate of the reaction as (I) increases, (D)
decreases, or (N) no change.
2CO(g) + O2(g)  2CO2 (g)
A. raising the temperature
B. removing O2
C. adding a catalyst
D. lowering the temperature

General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

© 2016 Pearson Education, Inc.

Solution

Indicate the effect of each factor listed on the rate of the reaction as (I) increases, (D)
decreases, or (N) no change.
2CO(g) + O2(g)  2CO2 (g)
A. raising the temperature
B. removing O2
C. adding a catalyst
D. lowering the temperature

General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

(I) increases
(D) decreases
(I) increases
(D) decreases

© 2016 Pearson Education, Inc.


Study Check

State the effect of each on the rate of reaction as (I) increases, (D) decreases, or (N)
no change.
A. decreasing the temperature
B. removing one of the reactants
C. adding a catalyst

D. placing the reaction flask in ice
E. increasing the concentration of a reactant

General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

© 2016 Pearson Education, Inc.


Study Check

State the effect of each on the rate of reaction as (I) increases, (D) decreases, or (N) no change.
A. decreasing the temperature

(D) decreases

B. removing one of the reactants

(D) decreases

C. adding a catalyst
D. placing the reaction flask in ice

(I) increases
(D) decreases

E. increasing the concentration of a
reactant

General, Organic, and Biological Chemistry: Structures of Life, 5/e

Karen C. Timberlake

(I) increases

© 2016 Pearson Education, Inc.


Chemistry Link to the Environment:
Catalytic Converters

Catalytic converters are used in automobile engines to reduce pollutants such as carbon monoxide (CO),
hydrocarbons such as octane (C8H18), and nitrogen oxide (NO).

General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

© 2016 Pearson Education, Inc.


Chemistry Link to the Environment:
Catalytic Converters

When pollutants pass through the surface, they react with the catalysts and are converted to CO 2, N2, O2,
and H2O.

General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

© 2016 Pearson Education, Inc.

General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

© 2016 Pearson Education, Inc.


10.2 Chemical Equilibrium

In most chemical reactions, the reactants are not completely converted to products
because a reverse reaction takes place in which products collide to form the reactants.

Learning Goal Use the concept of reversible reactions to explain chemical equilibrium.

General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

© 2016 Pearson Education, Inc.


Reversible Reactions

When a reaction proceeds in both a forward and a reverse direction, it is said to be a reversible reaction.
As the reactants, H2 and I2, collide, the forward reaction begins.

H2(g) + I2(g)
2HI(g)
HI molecules begin to form and collide with each other to form reactants in the reverse reaction. This
reversible reaction is written with a double arrow.

forward

H2(g) + I2(g)

2HI(g)
reverse

General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

© 2016 Pearson Education, Inc.


Reversible Reactions

A reversible reaction

•

occurs in both the forward and reverse direction at the same time.
forward
H2(g) + I2(g)
reverse

•

2HI (g)

has two rates, a rate for the forward reaction and a rate for the reverse reaction.

General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

© 2016 Pearson Education, Inc.


Study Check

Write the forward and reverse reactions for the following:

CH4(g) + 2H2S(g)

General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

CS2(g) + 4H2(g)

© 2016 Pearson Education, Inc.


Solution

Write the forward and reverse reactions for the following:

CH4(g) + 2H2S(g)

CS2(g) + 4H2(g)

The forward reaction is
CH4(g) + 2H2S(g)

CS2(g) + 4H2(g)

The reverse reaction is
CS2(g) + 4H2(g)

General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake

CH4(g) + 2H2S(g)

© 2016 Pearson Education, Inc.