Equilibrium, Redox Reactions,
Hydrocarbons, and Functional
Groups
Chapters 18,
20, 22, and 23
Jennie L. Borders
Chapter 18 – Reaction Rates
and Equilibrium
A
rate is a measure of the speed of any
change that occurs within an interval of
time.
 In chemistry, the rate of chemical change
or the reaction rate is usually expressed as
the amount of reactant changing per unit
of time.
Section 18.1 – Rate of Reaction
 According
to collision theory, particles
can react to form products when they
collide with one another, provided that
the colliding particles have enough
kinetic energy.
 The minimum energy that colliding
particles must have in order to react is
called the activation energy.
Activation Energy
Transition State
 An
activated complex is an unstable
arrangement of atoms that forms
momentarily at the peak of the
activation-energy barrier.
 The activated complex is sometimes
called the transition state.
Factors Affecting Reaction
Rates
 The
rate of a chemical reaction depends
upon temperature, concentration,
particle size, and use of a catalyst.
Temperature
 Usually,
raising the temperature speeds up
reactions.
 Increasing the temperature increases
both the frequency of collisions and the
number of particles that have enough
energy to slip over the activation-energy
barrier.
Concentration
 The
number of particles in a given volume
affects the rate at which reactions occur.
 More particles increase the concentration
which increase the number of collisions
leading to a higher reaction rate.
Particle Size
 The
surface area of a reactant affects the
reaction rate.
 The smaller the particle, the more surface
area.
 An increase in surface area increases the
amount of the reactant exposed for
reaction.
Catalysts
A
catalyst increases the rate of reaction
without being used up during the
reaction.
 Catalysts permit the reaction to proceed
along a lower energy path.
Catalyst vs. No Catalyst
catalyst
Catalysts
 Since
a catalyst is not consumed during a
reaction, it does not appear as a reactant
or a product.
 Instead, the catalyst is written above the
yield arrow.
Enzymes
 Enzymes
in your digestive
tract act as catalysts for
breaking down proteins.
 It takes your body a few
hours to digest proteins.
 Without the enzymes, it
would take many years for
you to digest your food.
Section 18.1 Assessment
1.
2.
3.
4.
How is the rate of a chemical reaction
expressed?
What are four factors that affect the rate
of a chemical reaction?
Does every collision between reaction
particles lead to products? Explain.
Why does refrigerated food stay fresh
longer than room temperature food?
Section 18.2 - Equilibrium
A
reversible reaction is one in which the
conversion of reactants to products and
the conversion of products to reactants
occur simultaneously.
Equilibrium
 When
the rates of the forward and
reverse reactions are equal, the reaction
has reached chemical equilibrium.
 At chemical equilibrium, no net change
occurs in the actual amounts of the
components of the system.
Position
 The
relative concentrations of the
reactants and products at equilibrium
constitute the equilibrium position of a
reaction.
 The equilibrium position indicates whether
the reactants or products are favored in a
reversible reaction.
Le Chatelier’s Principle
 Le
Chatelier’s Principle states that if a
stress is applied to a system in equilibrium,
the system changes in a way that relieves
the stress.
 Stresses that upset the equilibrium include
changes in the concentration of
reactants or products, change in
temperature, or changes in pressure.
Concentration
 Changing
the concentration of any
reactant or product at equilibrium disturbs
the equilibrium.
 The system adjusts to minimize the effects
of the change by shifting the equilibrium.
Temperature
 Increasing
the temperature causes the
equilibrium position to shift to the direction
that absorbs heat.
 Think of heat as a reactant or product in
the reaction.
Pressure
A
change in pressure only affects gaseous
equilibria that have an unequal number
of moles 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.
b.
c.
d.
Addition of Cl2
equilibrium shifts to the left
Increase in pressure equilibrium shifts to the left
Removal of heat
equilibrium shifts to the left
Removal of PCl3 as it is formed
equilibrium shifts to the right
Equilibrium Constant
 The
equilibrium constant (Keq) is the ratio
of the product concentration to reactant
concentration at equilibrium, with each
concentration raised to a power equal to
the number of moles of that substance in
the balanced chemical equation.
Equilibrium Constant
Generic Reaction:
aA + bB  cC + dD
Equilibrium Constant:
Keq = [C]c x [D]d
[A]a x [B]b
Equilibrium Constant
 Keq
> 1, products favored at equilibrium
 Keq < 1, reactants 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)
Keq = [NO2]2
[N2O4]
Keq = (0.030M)2 = 0.20
(0.0045M)
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
Keq =
[NH3]2
[N2][H2]3
Keq =
(0.10M)2 = 11.85
(0.25)(0.15)3
Section 18.2 Assessment
1.
2.
3.
How do the amounts of reactants and
products change after a reaction has
reached chemical equilibrium?
What are three stresses that can upset
the equilibrium of a chemical system?
What does the value of the equilibrium
constant tell you about the amounts of
reactants and products present at
equilibrium?
Section 18.2 Assessment
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
Chapter 20 – OxidationReduction Reactions
 Oxidation-reduction
reactions are also
known as redox reactions.
 Oxidation is the loss of electrons or the
gain of oxygen.
 Reduction is the gain of electrons or the
loss of oxygen.
Section 20.1 - Oxidation vs.
Reduction
 The
way to remember the difference in
oxidation and reduction is OIL RIG.
O = oxidation
I = is
L = loss of electrons
R = reduction
I = is
G = gain of electrons
Oxidation-Reduction
Reactions
Mg(s) + S(s)  Mg+2S-2(s)
Mg has a 0 charge and changes to Mg+2,
so it loses electrons and is oxidized.
S has a 0 charge and changes to S-2, so it
gains electrons and is reduced.
Oxidizing and Reducing Agents
 The
substance that loses electrons is
called the reducing agent.
 The substance that accepts electrons is
called the oxidizing agent.
 In other words, the substance that is
reduced is the oxidizing agent, and the
substance that is oxidized is the reducing
agent.
Sample Problem
Determine what is oxidized and what is
reduced. Identify the oxidizing agent and
the reducing agent.
2AgNO3(aq) + Cu(s)  Cu(NO3)2(aq) + 2Ag(s)
2Ag+NO3-(aq) + Cu0(s)  Cu+2(NO3-)2(aq) + 2Ag0(s)
Ag goes from +1 to 0, so it gains electrons. Cu
goes from 0 to +2, so it loses electrons.
Ag is reduced and is the oxidizing agent.
Cu is oxidized and is the reducing agent.
Practice Problem
Determine which substance is oxidized and
which is reduced. Identify the oxidizing
agent and the reducing agent.
4Al(s) + 3O2(g)  2Al2O3(s)
4Al0(s) + 3O20(g)  2Al2+3O3-2(s)
Al goes from 0 to +3, so it loses electrons. O
goes from 0 to -2, so it gains electrons.
Al is oxidized and is the reducing agent.
O is reduced and is the oxidizing agent.
Section 20.1 Assessment
1.
2.
3.
Define oxidation and reduction in terms
of loss or gain of oxygen.
Define oxidation and reduction in terms
of loss or gain of electrons.
How do you identify the oxidizing agent
and the reducing agent in a redox
reaction?
Section 20.1 Assessment
4. Determine which substance is oxidized
and which is reduced. Identify the oxidizing
agent and reducing agent.
Mg(s) + Cu(NO3)2(aq)  Mg(NO3)2(aq) + Cu(s)
Mg0(s) + Cu+2(NO3-)2(aq)  Mg+2(NO3-)2(aq) + Cu0(s)
Mg goes from 0 to +2, so it loses electrons. Cu goes
from +2 to 0, so it gains electrons.
Mg is oxidized and is the reducing agent.
Cu is reduced and is the oxidizing agent.
Section 20.2 – Oxidation Numbers
 An
oxidation number is a
positive or negative
number assigned to an
atom to indicate its degree
of oxidation or reduction.
 A bonded atom’s
oxidation number is the
charge that it would have
if the electrons in the
bonded were assigned to
the atom of the more
electronegative element.
Rules for Oxidation Numbers
1.
2.
3.
The oxidation number of a monatomic
ion is equal to its ionic charge.
Ex: Br- = -1
Fe+3 = +3
The oxidation number for H is +1 except
in metal hydrides where it is -1.
Ex: HCl, H = +1
NaH, H = -1
The oxidation number for oxygen is -2
except in peroxides where it is -1.
Ex: MgO, O = -2
H2O2, O = -1
Rules for Oxidation Numbers
4.
The oxidation number of a nonbonded
element is 0.
Ex: Ag = 0
5.
N2 = 0
For a neutral compound, the sum of the
oxidation numbers must equal 0.
Ex: NaCl = +1 and -1 equal 0.
H2O = 2(+1) and -2 equal 0.
6.
For a polyatomic ion, the sum of the oxidation
numbers must equal the ionic charge of the
ion.
Ex: CO3-2, O = -2, so C = +4
4 + (3 x -2) = -2
Oxidation Numbers
Sample Problem
What is the oxidation number of each
element in Na2SO4?
Na2SO4 = Na2+SO4-2 so Na is +1
SO4-2 = O is -2, so S has to be +6
Na=+1, O=-2, and S=+6
Practice Problems
1.
Assign the oxidation numbers for each
element in SO2.
SO2, O = -2, so S would be +4
O=-2 and S=+4
2.
Assign the oxidation number for each
element in (NH4)2S.
(NH4)2S = (NH4)2+S-2, so S = -2
NH4+, H = +1, so N would be -3
N=-3, H=+1, and S = -2
Oxidation Numbers
 In
some redox reactions, it is necessary to
look at oxidation numbers instead of just
using charges.
Sample Problem
Identify which atoms are oxidized and which
are reduced in the reaction.
2KNO3(s)  2KNO2(s) + O2(g)
+1 +5 -2
+1 +3 -2
0
2KNO3(s)  2KNO2(s) + O2(g)
Since N went from +5 to +3, it is reduced.
Since O went from -2 to 0, it is oxidized.
Practice Problem
Identify which atoms are oxidized and
which are reduced in the reaction.
2HNO3(aq) + 6HI(aq)  2NO(g) + 3I2(s) + 4H2O(l)
+1 +5 -2
+1 -1
+2 -2
0
+1
-2
2HNO3(aq) + 6HI(aq)  2NO(g) + 3I2(s) + 4H2O(l)
Since N goes form +5 to +2, it is reduced.
Since I goes form -1 to 0, it is oxidized.
Section 20.2 Assessment
1.
2.
What is the general rule for assigning
oxidation numbers?
Identify which atoms are oxidized and
which are reduced.
2Na(s) + Cl2(g)  2NaCl(s)
0
0
+1
-1
2Na(s) + Cl2(g)  2NaCl(s)
Since Na goes from 0 to +1, it is oxidized.
Since Cl goes from 0 to -1, it is reduced.
Chapter 22 – Hydrocarbon
Compounds
 Compounds
that contain carbon are
classified as organic compounds.
 The simplest organic compounds contain
only carbon and hydrogen and are
called hydrocarbons.
Section 22.1 - Hydrocarbons
 Because
carbon has four valence
electrons, a carbon atom always forms
four covalent bonds.
Alkanes
 An
alkane is a hydrocarbon in which there
are only single covalent bonds.
 The carbon atoms in an alkane can be
arranged in a straight chain or in a chain
that has branches.
Naming Alkanes
 The
following chart shows the names for straightchain alkanes containing 1 to 10 carbons.
# Carbon
Name
1
2
3
Methane
Ethane
Propane
Molecular
Formula
CH4
C2H6
C3H8
4
Butane
C4H10
5
6
7
8
Pentane
Hexane
Heptane
Octane
C5H12
C6H14
C7H16
C8H18
9
10
Nonane
Decane
C9H20
C10H22
Writing the Formulas for
Hydrocarbons
 Molecular
Formula
C6H14
Branched-Chain Alkanes
 An
atom or group of atoms that can take
the place of a hydrogen atom on a
parent hydrocarbon is called a
substituent.
 The longest continuous carbon chain of a
branched-chain hydrocarbon is called
the parent alkane.
Alkyl Group
A
hydrocarbon substituent is called an
alkyl group.
 Alkyl groups are named by removing the
–ane ending from the parent
hydrocarbon and adding –yl.
 Ex: methane = methyl
ethane = ethyl
Naming Branched-Chain
Alkanes
 The
IUPAC rules for naming branchedchain alkanes are based on the name of
the longest continuous carbon chain.
 Each alkyl substituent is named according
to the length of the chain and numbered
according to its position on the main
chain.
IUPAC Rules
1.
2.
3.
The longest chain is the parent chain.
Number the carbons in the parent chain
in order so that the groups attached to
the chain will have the smallest numbers.
Add numbers to the names of the
substituent groups to identify their
positions.
IUPAC Rules
4.
5.
6.
Use prefixes to indicate the appearance of the
same group more than once in the structural
formula.
List the names of the alkyl substituents in
alphabetical order, but ignore any prefixes.
Use proper punctuation.
Commas are used to
separate numbers, and
hyphens are used to
separate numbers and
words.
Sample Problems
 Name
the following compound.
7
1
6
2
5
3
4
4
3
5
2
6
1
7
4-ethyl-2,3-dimethylheptane
Sample Problems
 Name
the following compound.
6
5
4
3
2
1
2,3,4-trimethylhexane
Practice Problems
1.
Name the following compound.
4
3
2
5
6
1
7
4-ethyl-3,3,4-trimethylheptane
Practice Problems
1. Name the following compound.
4
3
5
2
6
1
7
4,4-diethylheptane
Drawing a Structural
Formula
1.
2.
3.
4.
Write the parent chain (the ending of
the name).
Number the carbons.
Attach the substituent groups.
Add hydrogens as needed until all
carbons have 4 bonds.
Sample Problem
1. Draw the structural formula for 2,2,4trimethylpentane.
1st draw pentane (5 carbons).
2nd add a methyl (-CH3) group to the 2, 2, and 4.
3rd fill in H’s until each C has 4 bonds.
CH3
CH3
I
I
CH3 - C - C H2 - C H - CH3
I
CH3
Practice Problem
1. Draw the structural formula for 4-ethyl2,3,4-trimethyloctane.
1st draw octane (8 carbons).
2nd add an ethyl (CH3CH2-) to 4 and a methyl (CH3-)
to 2, 3, and 4.
3rd add H’s until each C has 4 bonds.
CH2CH3
I
CH3- C H - CH - C - CH2 - C H2 - C H2- C H3
I
I
I
CH3 CH3 CH3
Section 22.1 Assessment
1.
2.
Explain why carbon atoms form four
covalent bonds.
Write the structural formula for the
following alkanes.
a. propane
3.
b. pentane
Draw the structural formula for 2,2dimethylbutane.
CH
3
I
CH3-C-CH2-CH3
I
CH3
Section 22.2 – Unsaturated
Hydrocarbons
 Organic
molecules that contain the
maximum amount of hydrogen atoms per
carbon atoms are called saturated
compounds.
 Compounds that contain double or triple
bonds are called unsaturated
compounds.
Alkane
R–CH2–CH2–R
Alkene
R–CH=CH–R
Alkyne
R–C≡C–R
Alkenes
 Alkenes
are hydrocarbons that contain
one or more carbon-carbon double
covalent bonds.
 When naming alkenes, find the longest
chain that includes the double bond and
change the ending of the alkane name
to –ene. Ex: butane = butene
Naming Alkenes
 The
carbons should be numbered so that
the double bonded carbons have the
lowest number.
 Any substituents should follow the rules
that we have already covered.
Alkynes
 Hydrocarbons
that contain one or more
carbon-carbon triple bonds are called
alkynes.
 Alkynes are named like alkenes, except
that the alkane name ending changes to
–yne. Ex: propane = propyne
Sample Problem
 Name
7
1
the following compound.
6
2
5 4
3 4
3
5
2
6
1
7
3-methyl-2-heptene
Practice Problem
 Name
1
the following compound.
2
3
CH3-CH2-C
CH3
4 5
6I
7
8
C-CH-CH-CH2-CH3
I
CH2CH3
5-ethyl-6-methyl-3-octyne
Section 22.2 Assessment
 Describe
the bonding between atoms in
an alkene.
 What types of bonds are present in an
alkyne?
 What is the difference between saturated
and unsaturated hydrocarbons?
Chapter 23 – Functional
Groups
 The
substituents of organic
molecules often contain
oxygen, nitrogen, sulfur,
and/or phosphorus.
 A functional group is a
specific arrangement of
atoms in an organic
compound that is
capable of characteristic
chemical reactions.
Section 23.1 – Functional
Groups
 The
symbol R represents any
carbon chains or rings attached to
the functional group.
 Double bonds and triple bonds are
also considered functional groups.
 A halocarbon is a carbon
containing compound with a
halogen substituent.
Functional Groups
phenyl
Functional Groups
Section 23.1 Assessment
1.
2.
What is a halocarbon?
Identify the functional group in each
structure.
a. CH3-OH
b. CH3-CH2-NH2
c.
C - OH
II
O
d. CH3-CH2-CH2-Br
e. CH3-CH2-O-CH2-CH3