Chemical Equilibrium

1
Chemical Equilibrium
I. A State of Dynamic Balance
1N2 (g)
3H2(g)

2NH3(g)
?G0 -33.1 kJ
The reaction is spontaneous under
standard conditions
The concentrations of the reactants decrease at
first
But, then, before the reactants are used up, all
concentrations become constant
while the concentration of the product increases
2
Chemical Equilibrium
I. A State of Dynamic Balance
-when a ________ results in the almost ________
conversion of ________ to ________, the
________ is said to go to __________, but _____
_________ ___ ____ go to __________, most
_________ are __________
reaction
complete
reactants
products
reaction
1N2 (g)
3H2(g)

2NH3(g)
completion
most
reactions
1N2 (g)
3H2(g)

2NH3(g)
do
not
completion
reactions
reversible
1N2 (g)
3H2(g)

2NH3(g)
At first, only the reactants are present, so only
the forward reaction can occur
1N2 (g)
3H2(g)

2NH3(g)
3
Chemical Equilibrium
I. A State of Dynamic Balance
-as soon as the ________ ________ begins, the
____________ of the _________ go _____, and the
_________ _____ goes _____ as the number of
__________ per unit ____ goes _____
forward
reaction
concentrations
reactants
down
reaction
rate
down
collisions
time
down
As soon as the products begin forming, the
forward reaction rate slows and the reverse
reaction begins
1N2 (g)
3H2(g)

2NH3(g)
4
Chemical Equilibrium
I. A State of Dynamic Balance
-as the _________ proceeds, the ____ of the
________ _________ continues to ________ and the
____ of the ________ ________ continues to
________ until the two _____ are _____, and the
system has reached a state of ________ __________
reaction
rate
forward
reaction
decrease
rate
reverse
reaction
increase
rates
equal
chemical
equilbrium
1N2 (g)
3H2(g)

2NH3(g)
5
Chemical Equilibrium
I. A State of Dynamic Balance
-at ___________, the ____________ of the
________ and ________ are not _____, but
_______, because the ____ of _________ of the
________ is _____ to the ____ of _________ of
the ________
equilibrium
concentrations
reactants
products
equal
constant
rate
formation
products
equal
rate
formation
reactants
The Golden Gate Bridge connects San Francisco to
Sausalito.
If all other roads leading in and out of the two
cities were closed
and the number of vehicles crossing the bridge
per hour in one direction equaled the number of
vehicles crossing the bridge in the
opposite direction
What is true of the number of vehicles in each
city throughout the day?
Are there the same number of vehicles in each
city?
6
Chemical Equilibrium
II. Equilibrium Expressions and Constants
-while _____ chemical systems have little
tendency to _____, and _____ chemical systems
_____ readily and ___ to __________, _____
chemical systems reach a _____ of __________,
leaving varying amounts of ________ ____________
some
react
some
react
go
completion
most
state
equilibrium
reactant
unconsumed
Waage
-in 1864, Norwegian chemists ______ and
_________ proposed the _______
___________________, which states, at a given
___________, a chemical system may reach a
_____ in which a particular _____ of _______
and _______ ____________ has a _______ value
Guldberg
Law of
Chemical Equilibrium
temperature
state
ratio
reactant
product
concentrations
constant
Peter Waage 1833-1900
Cato Maximilian Guldberg 1836-1902
7
Chemical Equilibrium
II. Equilibrium Expressions and Constants
-the _______ ________ for a _______ at
__________ can be written _______________________
_______, where __ and __ are ________, __ and
__ are ________, __, __, __, and __ are the
___________ in the ________ ________, and the
__________ _______ __________ is
general
equation
reaction
equilibrium
aA

bB
cC

dD
A
B
reactants
C
D
products
a
b
c
d
coefficients
balanced
equation
equilibrium
constant
expression
Cc
Dd
Keq

Aa
Bb
equilibrium
mixtures
Keq
-___________ ________ with ___ values __ __
contain more ________ than ________ at
___________, while __________ ________ with ___
values __ __ contain more ________ than
________ at __________
gt
1
products
reactants
equilibrium
equilibrium
mixtures
Keq
1
lt
reactants
products
equilibrium
8
Chemical Equilibrium
II. Equilibrium Expressions and Constants
Write the equilibrium constant expression for the
homogeneous equilibrium for the synthesis of
ammonia from nitrogen and hydrogen.
1N2 (g)
3H2(g)

2NH3(g)
The equilibrium is homogeneous because all the
reactants and products are in the same
physical state (gas)
Cc
Dd
Keq

Aa
Bb
Cc
NH3c
NH32
Keq



Aa
Bb
N2a
H2b
N21
H23
9
Chemical Equilibrium
II. Equilibrium Expressions and Constants
Write the equilibrium constant expression for the
equilibrium for the synthesis of Hydrogen iodide
from iodine and hydrogen.
1H2 (g)
1I2(g)

2HI(g)
The equilibrium is homogeneous because all the
reactants and products are in the same
physical state (gas)
Cc
Dd
Keq

Aa
Bb
Cc
HIc
HI2
Keq



Aa
Bb
H2a
I2b
H21
I21
10
Chemical Equilibrium
II. Equilibrium Expressions and Constants
Write the equilibrium constant expression for the
equilibrium for the decomposition of Dinitrogen
tetroxide into Nitrogen dioxide.
1N2O4 (g)
2NO2(g)
The equilibrium is homogeneous because all the
reactants and products are in the same
physical state (gas)
Cc
Dd
Keq

Aa
Bb
Cc
NO2c
NO22
Keq



N2O4a
Aa
N2O41
11
Chemical Equilibrium
II. Equilibrium Expressions and Constants
Write the equilibrium constant expression for the
equilibrium for the reaction of Carbon monoxide
and Hydrogen which produces methane
(Tetrahydrogen monocarbide) and water.
3H2 (g)
1CH4(g)
1CO(g)

1H2O (g)

Cc
Dd
Keq

Aa
Bb
Cc
CH4c
Dd
H2Od
CH41
H2O1
Keq



Aa
COa
Bb
H2b
CO1
H23
12
Chemical Equilibrium
II. Equilibrium Expressions and Constants
Write the equilibrium constant expression for the
equilibrium for the decomposition of Dihydrogen
monosulfide into diatomic hydrogen and diatomic
sulfur.
2H2S (g)
2H2 (g)
1S2 (g)

Cc
Dd
Keq

Aa
Bb
Cc
H2c
Dd
S2d
H22
S21
Keq



Aa
H2Sa
H2S2
13
Chemical Equilibrium
II. Equilibrium Expressions and Constants
-_________ in which all ________ and ________
are in the same ________ _____ are ____________,
but ________ with _________ and ________ in
_____ than ___ ________ _____ result in
_____________ _________
equilibria
reactants
products
physical
state
homogeneous
reactions
reactants
products
more
one
physical
state
heterogeneous
equilibria
gaseous ethanol
1C2H5OH (l)
1C2H5OH (g)
Cc
Dd
Keq

Aa
Bb
C2H5OH (g)1
Keq

C2H5OH (l)1
Keq

C2H5OH (g)1
liquid ethanol
14
Chemical Equilibrium
II. Equilibrium Expressions and Constants
-since ______ and _____ ________ and ________
dont change ___________, (which is really their
______), if the ___________ remains ________,
then in the ___________ _______ __________ for a
____________ ___________, the ___________
________ only depends on the ______________ of
the ________ and ________ in the _______ state
of matter
liquid
solid
reactants
products
concentration
density
temperature
constant
equilibrium
constant
expression
heterogeneous
equilibrium
equilibrium
constant
concentrations
reactants
products
gaseous
15
Chemical Equilibrium
II. Equilibrium Expressions and Constants
Write the equilibrium constant expression for the
heterogeneous equilibrium for the decomposition
of Sodium Hydrogen carbonate into Sodium
carbonate, Carbon dioxide, and water.
2NaHCO3 (s)
1Na2CO3 (s)

1CO2 (g)
1H2O (g)

The equilibrium is heterogeneous because the
reactants and products are in different
physical states (gas and solid)
Cc
Dd
Ee
Keq

Aa
Keq

Dd

CO2d
H2Oe

CO21
H2O1
Ee
16
Chemical Equilibrium
II. Equilibrium Expressions and Constants
Write the equilibrium constant expression for the
heterogeneous equilibrium for the decomposition
of Calcium carbonate into Calcium oxide and
Carbon dioxide.
1CaCO3 (s)
1CaO (s)

1CO2 (g)
The equilibrium is heterogeneous because the
reactants and products are in different
physical states (gas and solid)
Cc
Dd
Keq

Aa
Keq

Dd

CO2d

CO21
17
Chemical Equilibrium
II. Equilibrium Expressions and Constants
Write the complete, balanced thermochemical
equation and equilibrium constant expression for
the heterogeneous equilibrium for the reaction of
monatomic Sulfur and fluorine gas, which produces
Sulfur tetrafluoride gas and Sulfur hexafluoride
gas.
5F2 (g)
1SF4 (g)
2S (s)

1SF6 (g)

SF41
SF61
Keq

F25
18
Chemical Equilibrium
II. Equilibrium Expressions and Constants
Write the complete, balanced thermochemical
equation and equilibrium constant expression for
the homogeneous equilibrium for the reaction of
hydrazine (Tetrahydrogen dinitride) and Nitrogen
dioxide, which produces nitrogen and water.
2NO2 (g)
3N2 (g)
2N2H4 (g)

4H2O (g)

N23
H2O4
Keq

N2H42
NO22
19
Chemical Equilibrium
II. Equilibrium Expressions and Constants
Write the complete, balanced thermochemical
equation and equilibrium constant expression for
the homogeneous equilibrium for the reaction of
Sulfur trioxide and Carbon dioxide, which
produces Carbon disulfide and oxygen.
1CO2 (g)
1CS2 (g)
2SO3 (g)

4O2 (g)

CS21
O24
Keq

SO32
CO21
20
Chemical Equilibrium
II. Equilibrium Expressions and Constants
Write the complete, balanced thermochemical
equation and equilibrium constant expression for
the heterogeneous equilibrium for the reaction of
monatomic Sulfur and fluorine gas, which produces
Sulfur tetrafluoride gas and Sulfur hexafluoride
gas.
5F2 (g)
1SF4 (g)
2S (s)

1SF6 (g)

SF41
SF61
Keq

F25
21
Chemical Equilibrium
II. Equilibrium Expressions and Constants
Write the complete, balanced thermochemical
equation and equilibrium constant expression for
the heterogeneous equilibrium for the reaction of
magnatite (Fe3O4) and hydrogen gas, which
produces iron and water vapor.
4H2 (g)
3Fe (s)
1Fe3O4 (s)

4H2O (g)

H2O4
Keq

H24
22
Chemical Equilibrium
II. Equilibrium Expressions and Constants
Write the equilibrium constant expression for the
homogeneous equilibrium for the synthesis of
ammonia and calculate the value of Keq when NH3
0.933 M, N2 0.533 M, and H2 1.600 M.
1N2 (g)
3H2(g)

2NH3(g)
NH32
Keq

N21
H23
0.9332
Keq

0.5331
1.6003
Keq

0.399
23
Chemical Equilibrium
II. Equilibrium Expressions and Constants
Write the equilibrium constant expression for the
homogeneous equilibrium for the decomposition of
Sulfur trioxide into Sulfur dioxide and oxygen
gas, and calculate the value of Keq when SO3
0.0160 M, SO2 0.00560 M, and O2 0.00210 M.
2SO3 (g)
1O2 (g)

2SO2 (g)
SO22
O21
Keq

SO32
0.005602
0.002101
Keq

0.01602
Keq

2.58 x 10-4
24
Chemical Equilibrium
III. Le Châteliers Principle
1. Hypothesis
What is the effect of temperature on equilibrium?
2. Prediction
3. Gather Data
A. Safety
The surfaces of the hot plates and the water will
be hot enough to cause burns. Use caution.
Cobalt(II) chloride hexahydrate is toxic, with an
LD50 80mg/kg Avoid ingestion (dont eat or
drink it). Wash hands thoroughly with soap and
water before leaving lab. Ethanol is extremely
flammable. No open flame.
B. Procedure
1. Pick up a sheet of white construction paper
and an artists paintbrush.
25
Chemical Equilibrium
III. Le Châteliers Principle
3. Gather Data
B. Procedure
2. With a partner, using a top-loading
electronic balance, mass 0.3 grams
of CoCl26H2O, crush it into a fine powder
using a mortar and pestle, and place it in a test
tube.
3. Add 10 mL of ethanol to the test tube, cap,
and shake vigorously until CoCl26H2O
dissolves. If the solution is not light
pink, add water dropwise until it turns light
pink.
4. Use the solution to paint a winter scene on
your white construction paper, including a
pink-colored field of snow.
5. To simulate the coming of spring, warm your
painting over the hotplate in the fume hood.
Record your observations.
26
Chemical Equilibrium
III. Le Châteliers Principle
4. Analyze Data
4Cl- (aq)
1CoCl42-(aq)

6H2O (l)
1Co(H2O)62 (aq)

heat
Hexahydrate Co2 ion (pink)
chloride ion
Tetrachlorocobaltate ion (blue)
4Cl- (aq)
1CoCl42-(aq)

6H2O (l)
1Co(H2O)62 (aq)

Hexahydrate Co2 ion (pink)
chloride ion
Tetrachlorocobaltate ion (blue)
5. Draw Conclusions
27
Chemical Equilibrium
III. Le Châteliers Principle
-________ that reach __________ instead of going
to __________ do not ________ as much
reactions
equilibrium
completion
produce
-in 1888, ________________________ discovered
that there are ways to _______ _________ in
order to make _________ more __________
Henry-Louis Le Châtelier
control
equilibria
reactions
productive
-____________________ states that if a ______
(like a ______ in __________) is applied to a
system at __________, the system _____ in the
________ that _______ the _____
Le Châteliers Principle
stress
change
temperature
equilibrium
shifts
direction
relieves
stress
Henry-Louis Le Châtelier 1850-1936
28
Chemical Equilibrium
III. Le Châteliers Principle
-stressors that cause a shift in equilibrium
A. Changes in Concentration
Write the equilibrium constant expression for the
equilibrium for the reaction of Carbon monoxide
and Hydrogen to produce methane and water. Then,
calculate the Keq value when CO 0.30000 M,
H2 0.10000 M, and CH4 0.05900 M, and
H2O 0.02000 M.
3H2 (g)
1CH4(g)
1CO(g)

1H2O (g)

CH41
H2O1
Keq

CO1
H23
0.059001
0.020001
Keq


3.933

first equilibrium position
0.300001
0.100003
29
Chemical Equilibrium
III. Le Châteliers Principle
A. Changes in Concentration
increasing
concentration
-_________ the ____________ of ___ _________ the
_______ of _________ between ___ and ___,
_________ the _____ of the _______ _______
CO
increases
number
collisions
CO
H2
increasing
rate
forward
reaction
3H2 (g)
1CH4(g)
1CO(g)

1H2O (g)

-the system responds to the ______ of the
addition of _______ by forming more _______ to
bring the system back into equilbrium
stress
reactant
product
30
Chemical Equilibrium
III. Le Châteliers Principle
A. Changes in Concentration
3H2 (g)
1CH4(g)
1CO(g)

1H2O (g)

0.99254 M
0.07762 M
0.06648 M
0.02746 M
CH41
H2O1
Keq

CO1
H23
0.066481
0.027461
Keq


3.933

second equilibrium position
0.992541
0.077623
31
Chemical Equilibrium
III. Le Châteliers Principle
A. Changes in Concentration
increasing
concentration
-_________ the ____________ of a ________ causes
__________ to _____ to the ____ to _______ the
____ of formation of ______
reactant
equilbrium
shift
right
increase
rate
product
3H2 (g)
1CH4(g)
1CO(g)

1H2O (g)

3H2 (g)
1CH4(g)
1CO(g)

1H2O (g)

decreasing
concentration
-_________ the ____________ of a ________ causes
__________ to _____ to the ____ to _______ the
____ of formation of ______
product
equilbrium
shift
right
increase
rate
product
32
Chemical Equilibrium
III. Le Châteliers Principle
A. Changes in Concentration
Predict what should happen to the following
equilibrium if hydrogen bonding due to the
addition of acetone binds water and effectively
removes it from the products.
4Cl- (aq)
1CoCl42-(aq)

6H2O (l)
1Co(H2O)62 (aq)

Hexahydrate Co2 ion (pink)
chloride ion
Tetrachlorocobaltate ion (blue)
33
Chemical Equilibrium
III. Le Châteliers Principle
-stressors that cause a shift in equilibrium
A. Changes in Volume
-_________ the ______ of the _______ container,
according to ______, ________ the ________,
which in turn ________ the _____ of _________
between the ________ of the ________, _________
the _____ of the ________ _______
decreasing
volume
reaction
Boyle
increases
pressure
3H2 (g)
1CO(g)

increases
rate
collision
particles
reactants
increasing
rate
forward
reaction
1CH4(g)
1H2O (g)

shift
equilibrium
-the _____ in the _________ causes the _____ on
the system to be _______ as for every __ _____
of _______ _______ _________, only __ _____ of
_______ _______ are _________, which,
according to ________, occupies __ the ______,
which _________ the ________
stress
relieved
4
moles
gaseous
reactant
consumed
2
moles
gaseous
product
produced
Avogadro
½
volume
decreases
pressure
34
Chemical Equilibrium
III. Le Châteliers Principle
-stressors that cause a shift in equilibrium
Use Le Châteliers Principle to predict how each
of these changes would affect the ammonia
equilibrium system.
1N2 (g)
3H2(g)

2NH3(g)
a. removing hydrogen from the system
__________________________
equilibrium shifts to the left
1N2 (g)
3H2(g)

2NH3(g)
b. adding ammonia to the system
_______________________________
equilibrium shifts to the left
1N2 (g)
3H2(g)

2NH3(g)
35
Chemical Equilibrium
III. Le Châteliers Principle
-stressors that cause a shift in equilibrium
Use Le Châteliers Principle to predict how each
of these changes would affect the ammonia
equilibrium system.
1N2 (g)
3H2(g)

2NH3(g)
c. adding hydrogen to the system
_______________________________
equilibrium shifts to the right
1N2 (g)
3H2(g)

2NH3(g)
36
Chemical Equilibrium
III. Le Châteliers Principle
-stressors that cause a shift in equilibrium
How would decreasing the volume of the reaction
container affect each of these equilibria?
equilibrium shifts to the right
a.
_________________________
stress has no effect on equilibrium
1H2 (g)
1Cl2(g)

2HCl(g)
b.
_____________________________
equilibrium shifts to the left
2NOBr(g)
1Br2(g)

2NO(g)
c.
_________________________
37
Chemical Equilibrium
III. Le Châteliers Principle
-stressors that cause a shift in equilibrium
A. Changes in Temperature
-while _______ in _____________ and ________ in
_______ cause ______ in _________, they ___ ___
_______ the __________ _______, but a ______ in
___________ causes ______ in both the
__________ ________ and the __________ _______
changes
concentration
changes
volume
shifts
equilibria
do
not
change
equilibrium
constant
change
temperature
change
equilibrium
position
equilibrium
constant
38
Chemical Equilibrium
III. Le Châteliers Principle
-stressors that cause a shift in equilibrium
A. Changes in Temperature
-since the _______ for making _______ has a
_______ ____, the ________ _______ is
_________, and the _______ _______ is
__________, so ____ can be thought of as a
_______ in the ________ _______ and a _______
in the _______ _______
reaction
methane
negative
?H0
forward
reaction
exothermic
3H2 (g)
1CO(g)

reverse
reaction
endothermic
heat
product
reactant
forward
reaction
reverse
reaction
1CH4(g)
1H2O (g)


heat
?H0 -206.5 kJ
39
Chemical Equilibrium
III. Le Châteliers Principle
-stressors that cause a shift in equilibrium
A. Changes in Temperature
-_________ the __________ is like _______ more
_______ to the _______ in which _____ acts as a
_______ and is _____ ___, in this case, the
__________ _______ _______
increasing
temperature
adding
reactant
reaction
heat
used
up
reactant
endothermic
reverse
reaction
3H2 (g)
1CH4(g)
1CO(g)

1H2O (g)


heat
-__________ shifts to the _____, _________ the
___________ of _______ because _______ is a
_______ in the _______ _______
equilibrium
left
decreasing
concentration
methane
methane
reactant
reverse
reaction
40
Chemical Equilibrium
III. Le Châteliers Principle
-stressors that cause a shift in equilibrium
A. Changes in Temperature
-_________ the __________ is like ________
_______ from the _______ in which _____ acts as
a _______, in this case, the __________
_______ _______
decreasing
temperature
removing
reactant
reaction
heat
reactant
endothermic
reverse
reaction
3H2 (g)
1CH4(g)
1CO(g)

1H2O (g)


heat
-__________ shifts to the _____, _________ the
___________ of _______ because _______ is a
_______ in the _______ _______
equilibrium
right
increasing
concentration
methane
methane
product
forward
reaction
41
Chemical Equilibrium
III. Le Châteliers Principle
-stressors that cause a shift in equilibrium
In the following equilibrium, would you raise or
lower the temperature to get the following
results?
1C2H2 (g)
1H2O(g)

1CH3CHO(g)
?H0 -151 kJ
a. increase the amount of CH3CHO_________________
_____________
lower the temperature
1C2H2 (g)
1H2O(g)

1CH3CHO(g)

heat
b. decrease the amount of C2H2
________________________________
lower the temperature
1C2H2 (g)
1H2O(g)

1CH3CHO(g)

heat
42
Chemical Equilibrium
III. Le Châteliers Principle
-stressors that cause a shift in equilibrium
In the following equilibrium, would you raise or
lower the temperature to get the following
results?
1C2H2 (g)
1H2O(g)

1CH3CHO(g)
?H0 -151 kJ
c. increase the amount of H2O ___________________
______________
raise the temperature
1C2H2 (g)
1H2O(g)

1CH3CHO(g)

heat
43
Chemical Equilibrium
III. Le Châteliers Principle
-stressors that cause a shift in equilibrium
In the following equilibrium, what effect does
decreasing the volume of the reaction vessel have?
1CO(g)
1Fe3O4(s)

1CO2 (g)
3FeO(s)

__________________________________________________
__________________________________________________
__________________________________________________
________________________
None. The solids do not change their
concentrations, and the number of moles of
gaseous reactant equals the number of moles of
gaseous product
In the following equilibrium, what effect does
simultaneously increasing the temperature and the
pressure have?
1CO (g)
1Cl2(g)

1COCl2(g)
?H0 -151 kJ

heat
__________________________________________________
__________________________________________________
__________________________________________________
________________________
Cannot predict. An increase in temperature
causes a shift in the equilibrium to the left,
while an increase in pressure causes a shift in
equilibrium to the right.
44
Chemical Equilibrium
III. Le Châteliers Principle
1. Hypothesis
What is the effect of a change in concentration
of reactants and a change in temperature on
equilibrium?
2. Prediction
3. Gather Data
A. Safety
The surfaces of the hot plate will be hot enough
to cause burns. Use caution. Cobalt(II)
chloride hexahydrate is toxic, with an LD50
80mg/kg Avoid ingestion (dont eat or drink it).
Wash hands thoroughly with soap and water before
leaving lab. Concentrated Hydrochloric acid is
extremely corrosive. Avoid contact with eyes,
skin, and clothing. Goggles, aprons, and gloves
mandatory.
45
Chemical Equilibrium
III. Le Châteliers Principle
3. Gather Data
B. Procedure
1. With a partner, measure out 2 mL of 0.1 M
CoCl2 solution into a test tube. Record
initial color. __________
2. Add 3 mL (60 drops) of concentrated HCl to
the test tube. Record color. _____________
3. Add water dropwise to the test tube until a
color change occurs. Record color.
______________
4. Add 2 mL of 0.1 M CoCl2 solution to another
test tube. Add concentrated HCl dropwise
until the solution turns purple. If the
solution turns blue, add water until it turns
purple.
46
Chemical Equilibrium
III. Le Châteliers Principle
3. Gather Data
B. Procedure
5. Place the test tube in an ice bath. Record
color. ________
6. Place the test tube in a hot water bath.
Record color. ___________
4. Analyze Data
A. The equation for the reversible reaction in
this experiment is
heat
47
Chemical Equilibrium
III. Le Châteliers Principle
4. Analyze Data
A. Use the equation to explain the colors of the
solution in steps 1, 2, and 3
In Step 1, the solution is initially a pink
color, because the reaction arrives at an
equilibrium in which the concentration of the
pink-colored 1Co(H2O)62(aq) is at a higher
concentration than the blue-colored 1CoCl42-(aq).
In Step 2, the addition of HCl increases the
concentration of Cl-, shifting the equilibrium to
the right to favor the formation of the blue
1CoCl42-(aq), so the solution turns blue. In
Step 3, the increase in concentration of water
shifts the equilibrium left, re-establishing a
new equilbrium where the concentration of
1CoCl42-(aq) is higher than it was orginally, so
the purple color shows more of a balance of pink
and blue.
48
Chemical Equilibrium
III. Le Châteliers Principle
4. Analyze Data
B. Explain how the equilibrium shifts when heat
energy is added or removed.
In Step 5, since heat acts like a product in the
exothermic reverse reaction, removing heat by
lowering the temperature causes the equilibrium
to shift to the left, increasing the rate of the
reverse reaction and causing the solution to turn
pink. In Step 6, since heat acts like a reactant
in the endothermic forward reaction, adding heat
by increasing the temperature causes the
equilibrium to shift to the right, increasing the
rate of the forward reaction and causing the
solution to turn blue.
5. Draw Conclusions
49
Chemical Equilibrium
IV. Using Equilibrium Constants
-when a ________ has a _____ ___, the __________
_______ contains _____ ________ than ________
at __________
reaction
large
Keq
equilibrium
mixture
more
products
reactants
equilibrium
-when a ________ has a _____ ___, the __________
_______ contains _____ ________ than ________
at __________
reaction
small
Keq
equilibrium
mixture
more
reactants
products
equilibrium
A. Calculating Equilibrium Concentrations
-__________ ________ can also be used to
________ the __________ ____________ of
any ________ in the _______
equilibrium
constants
calculate
equilibrium
concentration
substance
reaction
50
Chemical Equilibrium
IV. Using Equilibrium Constants
A. Calculating Equilibrium Concentrations
At 1200 K, the Keq for the following reaction
equals 3.933. What is the concentration of the
methane produced, if CO 0.850 M, H2 1.333
M, and H2O 0.286 M?
3H2 (g)
1CH4(g)
1CO(g)

1H2O (g)

1.333 M
0.850 M
? M
0.286 M
CH41
H2O1
Keq

CO1
H23
CH41
0.2861
3.933

0.8501
1.3333

27.7 M
CH4
51
Chemical Equilibrium
IV. Using Equilibrium Constants
A. Calculating Equilibrium Concentrations
At 1405 K, the Keq for the following reaction
equals 2.27 x 10-3. What is the concentration of
the Hydrogen gas produced, if S2 0.0540 M,
and H2S 0.184 M?
2H2S (g)
2H2(g)
1S2 (g)

0.184 M
? M
0.0540 M
H22
S21
Keq

H2S2
H22
0.05401
2.27 x 10-3

0.1842

0.0377 M
H2
52
Chemical Equilibrium
IV. Using Equilibrium Constants
A. Calculating Equilibrium Concentrations
If Keq for the following reaction equals 10.5,
what is the equilibrium concentration of Carbon
monoxide, if H2 0.933 M, and CH3OH 1.32 M?
2H2 (g)
1CO(g)

1CH3OH (g)
0.933 M
? M
1.32 M
CH3OH1
Keq

CO1
H22
1.321
10.5

CO1
0.9332

0.144 M
CO
53
Chemical Equilibrium
IV. Using Equilibrium Constants
A. Calculating Equilibrium Concentrations from
Initial Concentrations Using ICE (Initial,
Change, Equilibrium)
If the Keq for the following reaction equals
64.0, what are the equilibrium concentrations of
I2, H2, and HI, if I20 0.200 M, H20 0.200
M and HI 0.000 M?
1H2 (g)
2HI(g)
1I2(g)

? M
? M
? M
H2
I2
HI
Initial
0.200
0.200
0.000
Change
-1x
-1x
2x
Equilibrium
0.200 - 1x
0.200 - 1x
2x
54
Chemical Equilibrium
IV. Using Equilibrium Constants
A. Calculating Equilibrium Concentrations from
Initial Concentrations Using ICE (Initial,
Change, Equilibrium)
1H2 (g)
2HI(g)
1I2(g)

H2
I2
HI
Initial
0.200
0.200
0.000
Change
-1x
-1x
2x
Equilibrium
0.200 - 1x
0.200 - 1x
2x
HI2
2x
Keq

8.00

x

0.160
I21
H21
0.200 1x1
H2

0.040 M
2x2
I2

0.040 M
64.0

0.200 1x1
0.200 1x1
HI

0.320 M
55
Chemical Equilibrium
IV. Using Equilibrium Constants
A. Calculating Equilibrium Concentrations from
Initial Concentrations Using ICE (Initial,
Change, Equilibrium)
If the Keq for the following reaction equals
16.0, what are the equilibrium concentrations of
PCl3, Cl2, and PCl5, if PCl50 1.00 M?
1Cl2 (g)
1PCl5(g)
1PCl3(g)

? M
? M
? M
PCl3
Cl2
PCl5
Initial
0.00
0.00
1.00
Change
1x
1x
-1x
Equilibrium
0.00 1x
0.00 1x
1.00 1x
56
Chemical Equilibrium
IV. Using Equilibrium Constants
A. Calculating Equilibrium Concentrations from
Initial Concentrations Using ICE (Initial,
Change, Equilibrium)
1Cl2 (g)
1PCl5(g)
1PCl3(g)

PCl3
Cl2
PCl5
Initial
0.00
0.00
1.00
Change
1x
1x
-1x
Equilibrium
0.00 1x
0.00 1x
1.00 1x
PCl31
Cl21
Keq

x2

16.0 16.0x
x

-b

PCl51
x2

16.0x
-
16.0

0
2a
x1
x1
ax2

bx

c

0
16.0

1.00 - x1
57
Chemical Equilibrium
IV. Using Equilibrium Constants
A. Calculating Equilibrium Concentrations from
Initial Concentrations Using ICE (Initial,
Change, Equilibrium)
x

-b

x2

16.0x
-
16.0

0
2a
ax2

bx

c

0
x

-16.0

2(1.00)
x

0.950
(but not -17.0)
PCl3

0.950 M
Cl2

0.950 M
PCl5

0.05 M
58
Chemical Equilibrium
IV. Using Equilibrium Constants
A. Calculating Equilibrium Concentrations from
Initial Concentrations Using ICE (Initial,
Change, Equilibrium)
If the Keq for the following reaction equals
0.680, what are the equilibrium concentrations of
COCl2, CO, and Cl2, if CO0 0.500 M and Cl20
1.00 M?
1Cl2 (g)
1CO (g)
1COCl2 (g)

? M
? M
? M
COCl2
CO
Cl2
Initial
0.00
0.500
1.00
Change
1x
-1x
-1x
Equilibrium
0.00 1x
0.500 - 1x
1.00 1x
59
Chemical Equilibrium
IV. Using Equilibrium Constants
A. Calculating Equilibrium Concentrations from
Initial Concentrations Using ICE (Initial,
Change, Equilibrium)
1Cl2 (g)
1CO (g)
1COCl2 (g)

COCl2
CO
Cl2
Initial
0.00
0.500
1.00
Change
1x
-1x
-1x
Equilibrium
0.00 1x
0.500 - 1x
1.00 1x
COCl21
Keq

x

0.340 - 0.340x 0.680x x2
Cl21
CO1
0.680x2
-
2.02x

0.340

0
x1
ax2

bx

c

0
0.680

1.00 - x1
0.500 - x1
60
Chemical Equilibrium
IV. Using Equilibrium Constants
A. Calculating Equilibrium Concentrations from
Initial Concentrations Using ICE (Initial,
Change, Equilibrium)
x

-b

0.680x2
-
2.02x

0.340

0
2a
ax2

bx

c

0
x

2.02

2(0.680)
x

2.79
or 0.176
COCl2

0.176 M
CO

0.324 M
Cl2

0.82 M
x

0.176
61
Chemical Equilibrium
IV. Using Equilibrium Constants
A. Calculating Equilibrium Concentrations from
Initial Concentrations Using ICE (Initial,
Change, Equilibrium)
If the Keq for the following reaction equals
36.0, what are the equilibrium concentrations of
H2, Br2, and HBr, if H20 0.250 M and Br20
0.250 M?
1Br2 (g)
2HBr(g)
1H2(g)

? M
? M
? M
H2
Br2
HBr
Initial
0.250
0.250
0.000
Change
-1x
-1x
2x
Equilibrium
0.250 - 1x
0.250 - 1x
0.000 2x
62
Chemical Equilibrium
IV. Using Equilibrium Constants
A. Calculating Equilibrium Concentrations from
Initial Concentrations Using ICE (Initial,
Change, Equilibrium)
1Br2 (g)
2HBr (g)
1H2 (g)

H2
Br2
HBr
Initial
0.250
0.250
0.000
Change
-1x
-1x
2x
Equilibrium
0.250 - 1x
0.250 - 1x
0.000 2x
HBr2
2x
Keq

6.00

H21
Br21
(0.250 x)
x

0.188
2x2
36.0

0.250 - x1
0.250 - x1
63
Chemical Equilibrium
IV. Using Equilibrium Constants
A. Calculating Equilibrium Concentrations from
Initial Concentrations Using ICE (Initial,
Change, Equilibrium)
32x2
-
18.0x

2.25

0
x

-b

2a
ax2

bx

c

0
x

18.0

2(32)
x

0.375
or 0.188
H2

0.062 M
Br2

0.062 M
HBr

0.376 M
64
Chemical Equilibrium
V. Solubility Equilibria
-like a few _________ _________ that go to
_________, upon __________, some ______
__________ _________ completely into _____
chemical
reactions
completion
dissolving
ionic
compounds
dissociate
ions
1NaCl (s)
1Na (aq)

1Cl- (aq)
-some _____ __________, however, are only
________ _______, and quickly reach a ________
__________
ionic
compounds
sparingly
soluble
solubility
equilibrium
1BaSO4 (s)
1Ba2 (aq)

1SO42- (aq)
SO42-1
Ba2 1
Keq

BaSO41
65
Chemical Equilibrium
V. Solubility Equilibria
-in the __________ _______ __________, ______
______ is a _____, so the _______ is _______,
and can be combined with the ___ value to form
the ________ _______ _______
equilibrium
constant
expression
Barium
sulfate
solid
BaSO4
constant
Keq
solubility
product
constant
Keq

SO42-1
Ba2 1
BaSO41
x
Ksp

SO42-1
Ba2 1
Write the solubility constant expression for the
following solubility equilibrium
1Mg(OH)2 (s)
1Mg2 (aq)

2OH- (aq)
Ksp

OH-2
Mg2 1
66
Chemical Equilibrium
V. Solubility Equilibria
A. Calculating Solubilities from
Solubility Product Constants
What is the solubility, in M, of Silver iodide at
298 K?
1AgI (s)
1Ag (aq)

1I- (aq)
Ksp

I-1
Ag 1
8.5 x 10-17

I-1
Ag 1
8.5 x 10-17

s2

s

9.2 x 10-9 M
67
Chemical Equilibrium
V. Solubility Equilibria
A. Calculating Solubilities from
Solubility Product Constants
What is the solubility, in M, of Copper(II)
carbonate at 298 K?
1CuCO3 (s)
1Cu2 (aq)

1CO32- (aq)
Ksp

CO32-1
Cu2 1
2.5 x 10-10

CO32-1
Cu2 1
2.5 x 10-10

s2

s

1.6 x 10-5 M
68
Chemical Equilibrium
V. Solubility Equilibria
B. Calculating Ion Concentration from Ksp
What is OH- at 298 K in a saturated solution of
Mg(OH)2 at equilibrium?
1Mg(OH)2 (s)
1Mg2 (aq)

2OH- (aq)
Ksp

OH-2
Mg2 1
let x

Mg2
so 2x

OH-
5.6 x 10-12

(x)
(2x)2
5.6 x 10-12

4x3
1.4 x 10-12

x3

x
1.1 x 10-4

x
2.2 x 10-4

2x

OH-
69
Chemical Equilibrium
V. Solubility Equilibria
B. Calculating Ion Concentration from Ksp
What is Ag at 298 K in a saturated solution of
AgBr at equilibrium?
1AgBr (s)
1Ag (aq)

1Br- (aq)
Ksp

Br-1
Ag 1
let x

Ag
so x

Br-
5.4 x 10-13

x2

x
7.3 x 10-7

x

Ag
70
Chemical Equilibrium
V. Solubility Equilibria
B. Calculating Ion Concentration from Ksp
What is F- at 298 K in a saturated solution of
CaF2 at equilibrium?
1CaF2 (s)
1Ca2 (aq)

2F- (aq)
Ksp

F-2
Ca2 1
3.5 x 10-11

(x)
(2x)2
3.5 x 10-11

4x3
8.8 x 10-12

x3

x
2.1 x 10-4

x
4.2 x 10-4

2x

F-
71
Chemical Equilibrium
V. Solubility Equilibria
C. Predicting Precipitates
-besides being used to calculate the _________
of an _____ _________ and the ___________ of
____ in a _________ _______, ___ values can be
used to _______ if a _________ will form if ___
_____ __________ are mixed
solubility
ionic
compound
concentration
ions
saturated
solution
Ksp
predict
precipitate
two
ionic
compounds
Predict whether PbCl2 will form as a precipitate
if 100 mL of 0.0100 M NaCl is added to 100 mL of
0.0200 M Pb(NO3)2
concentrations
initial
-the ____________ of the ______ ________ allow
you to _______ the ____________ of ____ and ___
ions in the _____ _________, which when
_________ together, determine the ___ _______,
or ___
solutions
calculate
concentrations
Pb2
Cl-
mixed
solutions
multiplied
ion
product
Qsp
72
Chemical Equilibrium
V. Solubility Equilibria
C. Predicting Precipitates
Predict whether PbCl2 will form as a precipitate
if 100 mL of 0.0100 M NaCl is added to 100 mL of
0.0200 M Pb(NO3)2
1PbCl2 (s)
1Pb2 (aq)

2Cl- (aq)
Qsp

Cl-2
Pb21
Pb2

0.0200 M

0.0100 M
2
Cl-

0.0100 M

0.00500 M
2
Qsp

0.005002
0.01001
Qsp

2.50 x 10-7
lt
1.7 x 10-5

Ksp
73
Chemical Equilibrium
V. Solubility Equilibria
C. Predicting Precipitates
-if the ___ is ___ the ___, the _______ is
__________, and a _________ ____ ___ ____, and
if the ___ is ___ the ___, the _______ is
_________ and ___ ______ will occur, but if ___
is ___ the ___, a __________ will form, reducing
the ___ ___________ until ___ ___ ___, and the
system arrives at __________ and the _______
becomes ________
Qsp
lt
Ksp
solution
unsaturated
precipitate
will
not
form
Qsp

Ksp
solution
saturated
no
change
Qsp
Ksp
gt
precipitate
Qsp
Ksp
ion
concentration

equilibrium
solution
saturated
Qsp

2.50 x 10-7
lt
1.7 x 10-5

Ksp
No precipitate should form
74
Chemical Equilibrium
V. Solubility Equilibria
C. Predicting Precipitates
Predict whether Ag2SO4 will form as a precipitate
if 500 mL of 0.010 M AgNO3 is added to 500 mL of
0.25 M K2SO4
1Ag2SO4 (s)
2Ag (aq)

1SO42- (aq)
Qsp

SO42-1
Ag2
Ag

0.010 M

0.0050 M
2
SO42-

0.25 M

0.012 M
2
Qsp

0.0121
0.00502
Qsp

3.0 x 10-7
lt
1.2 x 10-5

Ksp
No precipitate should form
75
Chemical Equilibrium
V. Solubility Equilibria
C. Predicting Precipitates
Predict whether a precipitate will form if 200 mL
of 0.20 M MgCl2 is added to 200 mL of 0.0025 M
NaOH
1Mg(OH)2 (s)
1Mg2 (aq)

2OH- (aq)
Qsp

OH-2
Mg21
Mg2

0.20 M

0.10 M
2
OH-

0.0025 M

0.0012 M
2
Qsp

0.00122
0.101
Qsp

1.4 x 10-7
gt
5.6 x 10-12

Ksp
A precipitate of Mg(OH)2 should form
76
Chemical Equilibrium
V. Solubility Equilibria
D. Common Ion Effect
-the ________ of _______ in _____ is ________
mol/L, which means that you can ________
________ of _______ in ____ L of _____ _____,
but _________ of _______ will ____ _______ in
____ L of a ______ solution of _______, because
of the ________ ___ ______
solubility
PbCrO4
water
4.8 x 10-7
dissolve
4.8 x 10-7
PbCrO4
1.00
pure
water
4.8 x 10-7
PbCrO4
not
dissolve
1.00
0.10 M
K2CrO4
common
ion
effect
1PbCrO4 (s)
1Pb2 (aq)

1CrO42- (aq)
Ksp

CrO42-1
Pb21

2.3 x 10-13
product
concentrations
-since the _______ of the ____________ of both
____ is _____ to a _______, (the _________
_______ _______), if _______ goes __, _____ must
go _____
ions
equal
constant
solubility
product
constant
CrO42-
Pb2
up
down
77
Chemical Equilibrium
V. Solubility Equilibria
D. Common Ion Effect
-adding a _______ to an __________ that
contains a ________ ___ _______ the ________ of
a _________ containing that ___, or, according
to _____________ ________, stresses the
__________ and causes the _______ to _____ the
__________ in the _______ that _______ the
______
solution
equilibrium
common
ion
lowers
solubility
substance
ion
Le Châteliers
Principle
equilibrium
system
shift
equilibrium
direction
relieves
stress
1PbCrO4 (s)
1Pb2 (aq)

1CrO42- (aq)
78
Chemical Equilibrium
Chemical Equilibrium
V. Solubility Equilibria
1. Hypothesis
How Do Solubility Product Constants Compare?
2. Prediction
3. Gather Data
A. Safety
Silver nitrate stains skin and clothing and is
highly toxic, with an LD50 50mg/kg Avoid
ingestion (dont eat or drink it). Wash hands
thoroughly with soap and water before leaving
lab. Goggles mandatory.
B. Procedure
1. Using a pipette, place 20 drops of AgNO3
solution into test well A1 of a 20-well
microplate. Place 20 more drops of the
same solution in test well A2.
79
Chemical Equilibrium
V. Solubility Equilibria
3. Gather Data
B. Procedure
2. Add 10 drops of NaCl solution to both test
well A1 and test well A2. Record
observations___________________
3. To test well A2 only, add 10 drops of Na2S
solution. Record observations________________
______________
4. Compare the contents of test wells A1 and A2.
Record observations_________________________
____________
80
Chemical Equilibrium
V. Solubility Equilibria
4. Analyze Data
A. Write the complete thermochemical equation
for the reaction that occurred in Step 2.
B. Write the net ionic equation for the reaction
in Step 2.
C. Write the equation for the solubility
equilibrium that was established in test
wells A1 and A2 during Step 2.
D. Write the solubility constant expression for
the equilibrium established in test wells
A1 and A2 during Step 2.
E. Write the equation for the solubility
equilibrium that was established in test
well A2 during Step 4.
81
Chemical Equilibrium
V. Solubility Equilibria
4. Analyze Data
F. Match the chemical formula of each
precipitate with its color.
G. Compare the two Ksp values for the two
precipitates. Infer which is the more
soluble.
H. Use Le Châteliers Principle to explain how
the addition of Na2S in Step 4 affected the
equilibrium in test well A2.
82
Chemical Equilibrium
V. Solubility Equilibria
4. Analyze Data
I. Calculate the molar solubilities of both
precipitates in the experiment. Which of the
precipitates is more soluble?
83
Chemical Equilibrium
V. Solubility Equilibria
4. Analyze Data
A. Write the complete thermochemical equation
for the reaction that occurred in Step 2.
AgNO3 (aq) NaCl (aq) ? AgCl (s) NaNO3
(aq)
B. Write the net ionic equation for the reaction
in Step 2.
C. Write the equation for the solubility
equilibrium that was established in test
wells A1 and A2 during Step 2.
D. Write the solubility constant expression for
the equilibrium established in test wells
A1 and A2 during Step 2.
Ksp Ag1 Cl-1 1.8 x 10-10
E. Write the equation for the solubility
equilibrium that was established in test
well A2 during Step 4.
84
Chemical Equilibrium
V. Solubility Equilibria
4. Analyze Data
F. Match the chemical formula of each
precipitate with its color.
AgCl (s) is white Ag2S (s) is black
G. Compare the two Ksp values for the two
precipitates. Infer which is the more
soluble.
Ksp for AgCl (s) 1.8 x 10-10 Ksp for Ag2S
(s) 8 x 10-48 AgCl is more soluble
H. Use Le Châteliers Principle to explain how
the addition of Na2S in Step 4 affected the
equilibrium in test well A2.
The addition of S2- to the equilibrium removes
Ag from the equilibrium, causing the system to
shift to the right in favor of the formation of
Ag, so at the same time the black precipitate
Ag2S is forming, the white AgCl is dissolving to
relieve the stress on the equilibrium.
85
Chemical Equilibrium
V. Solubility Equilibria
4. Analyze Data
I. Calculate the molar solubilities of both
precipitates in the experiment. Which of the
precipitates is more soluble?
1AgCl (s)
1Ag (aq)

1Cl- (aq)
1Ag2S (s)
2Ag (aq)

1S2- (aq)
Ksp

Cl-1
Ag 1
Ksp

S2-1
Ag 2
1.8 x 10-10

Cl-1
Ag 1
8 x 10-48

S2-1
Ag 2
1.8 x 10-10

s2
8 x 10-48

4s3


s

1.3 x 10-5 M
s

1 x 10-16 M
AgCl is more soluble