Download Equilibrium

Equilibrium
Notes
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
Approaching Equilibrium
LeChatelier's Principle-1
LeChatelier's Principle-2
LeChatelier's-3 & Start Lab
Lab Lechatelier's
Haber/Graphing
Equilibrium Constants
Keq Calculations
K-trial & Size Keq
Entropy & Enthalpy
Review
Review
Worksheets
Quiz
WS 1
WS 2
WS 3
WS 4 and 5
Questions 1-10
WS 6 & 7
WS 8
WS 9 & 10
WS 11
WS 12
Web Review
Practice Test 2
Q1
Q2
Conclusion
Q3
Q4
Q5
Q6
Practice Test 1
Quizmebc
Worksheet #1
Approaching Equilibrium
1.
What are the conditions necessary for equilibrium?
2.
What is a forward reaction versus a reverse reaction?
3.
Why does the forward reaction rate decrease as equilibrium is approached?
4.
What are the characteristics of equilibrium?
5.
Define equilibrium.
6.
Define the word dynamic and explain its relevance to the concept of equilibrium.
7.
Why does the reverse reaction rate increase as equilibrium is approached?
As a reaction is approaching equilibrium describe how the following change. Explain what
causes each change.
8.
Reactant concentration.
9.
Products concentration.
10.
Forward reaction rate.
11.
Reverse reaction rate.
12.
What is equal at equilibrium?
13.
What is constant at equilibrium?
14.
Sketch each graph to show how concentrations change as equilibrium is approached
[Reactant]
15.
[Product]
Overall Rate
Label each graph with the correct description.

The forward and reverse rates as equilibrium is approached

The overall rate as equilibrium is approached

The reactant and product concentrations as equilibrium is approached (two graphs)
LeChatelier’s Principle
Worksheet #2
Describe the changes that occur after each stress is applied to the equilibrium.
N2 (g) +
Stress
1. [N2] is increased
2. [H2] is increased
3. [NH3] is increased
4. Temp is increased
5. [N2] is decreased
6. [H2] is decreased
7. [NH3] is decreased
8. Temp is decreased
9. A catalyst is added
[N2]
3H2 (g)
⇄
[H2]
2NH3(g) + 92 KJ
[NH3]
Shifts
Right or Left
Shifts to the
Reactants or Product
N2O4 (g)
Stress
⇄
H = + 92 KJ
2NO2(g)
[N2O4] [NO2]
Shifts
Right or Left
Shifts to Favour the
Reactants or Products
1. [N2O4] is increased
2. [NO2] is increased
3. Temp is increased
4. [N2O4] is decreased
5. [H2] is decreased
6. [NO2] is decreased
7. Temp is decreased
4HCl (g) +
O2 (g)
Stress
1. [HCl] is increased
2. [H2O] is increased
3. [O2] is increased
4. Temp is increased
5. [H2O] is decreased
6. [HCl ] is decreased
7. [O2] is decreased
8. Temp is decreased
9. A catalyst is added
⇄
[O2]
2H2O(g) +
[H2O]
2Cl2 (g) + 98 KJ
[HCl]
Shifts
Shifts to Favour the
Right or Left Reactants or Products
CaCO3 (s) + 170 KJ ⇄
CaO (s) + CO2
(g)
Note : Adding solids or liquids and removing solids or liquids does not shift the
equilibrium. This is because you cannot change the concentration of a pure liquid or solid as they
are 100% pure. It is only a concentration change that will change the # of collisions and hence
shift the equilibrium.
Shifts
Shifts to Favor the
Stress
[CO2]
Right or Left
Reactants or Products
1. CaCO3 is added
2. CaO is added
3. CO2 is added
4. Temp is decreased
5. A catalyst is added
6. [CO2] is decreased
7. Temp is increased
8. CaO is removed
Worksheet #3
Applying Le Châtelier's Principle
The oxidation of ammonia is a reversible exothermic reaction that proceeds as follows:
4 NH3 (g) + 5 O2 (g)
⇄
4 NO (g) + 6 H2O (g)
For each situation described in the table, indicate an increase or decrease in overall concentration
from before to after a new equilibrium has been established.
Component
Stress
Equilibrium Concentrations
NH3]
[O2]
[NO]
[H2O]
NH3
addition
removal
O2
addition
removal
NO
addition
removal
addition
removal
H2O
4 NH3 (g) + 5 O2 (g)
⇄
[NH3]
[O2]
4 NO (g) + 6 H2O (g)
[NO]
[H2O]
Increase in temperature
Decrease in temperature
Increase in pressure
Decrease in pressure
Addition of a catalyst
An Inert gas is added
State the direction in which each of the following equilibrium systems would be shifted upon
the application of the following stress listed beside the equation.
1. 2 SO2 (g) + O2 (g)
⇄
2. C (s) + CO2 (g) + energy
3. N2O4 (g)
⇄
2 SO3 (g) + energy
decrease temperature
⇄
increase temperature
2 CO (g)
2 NO2 (g)
increase total pressure
4. CO (g) + H2O (g)
⇄
decrease total pressure
5. 2 NOBr (g) ⇄
2 NO (g) + Br2 (g)
6. 3 Fe (s) + 4 H2O (g) ⇄
7. 2 SO2 (g) + O2 (g)
8. CaCO3 (s)
⇄
9. N2 (g) + 3 H2 (g)
⇄
CO2 (g) + H2 (g)
decrease total pressure
Fe3O4 (s) + 4 H2 (g)
add Fe(s)
2 SO3 (g)
add catalyst
CaO (s) + CO2 (g)
remove CO2 (g)
⇄
He is added
2 NH3 (g)
Consider the following equilibrium system:
3 H2 (g) + N2 (g) ⇄ 2 NH3 (g) + Heat.
State what affect each of the following will have on this system:
10.
More N2 is added to the system
11.
Some NH3 is removed from the system
12.
The temperature is increased
13.
The volume of the vessel is increased
14.
A catalyst was added
15.
An inert gas was added at constant
If a catalyst was added to the above reaction and a new equilibrium was established.
Compare to the original system, the rates of the forward and reverse reactions of the new
equilibrium.
Forward Rate has
16.
If the temperature was increased in the above reaction and a new equilibrium was
established. Compare to the original system, the rates of the forward and reverse
reactions of the new equilibrium.
Forward Rate has
17.
Reverse Rate has
Reverse Rate has
If the volume of the container was increased in the above reaction and a new equilibrium
was established. Compare to the original system, the rates of the forward and reverse
reactions of the new equilibrium.
Forward Rate has
Reverse Rate has
.
Consider the following equilibrium system
H2 (g) + I2 (g) ⇄ 2 HI (g)
State what affect each of the following will have on this system in terms of shifting.
18.
The volume of the vessel is increased
19.
The pressure is increased
20.
A catalyst is added
Consider the following equilibrium system:
3 Fe (s) + 4 H2O (g) ⇄ Fe3O4 (s) + 4 H2 (g)
State what affect each of the following will have on this system in terms of shifting.
21.
22.
23.
24.
The volume of the vessel is decreased
The pressure is decreased
More Fe is added to the system
Some Fe3O4 is removed from the system
25.
A catalyst is added to the system
Consider the following equilibrium:
2NO (g) + Br2 (g) + energy ⇄ 2NOBr (g)
State what affect each of the following will have on this system in terms of shifting.
26.
27.
The volume of the vessel is increased
The pressure is decreased
28.
29.
30.
More Br2 is added to the system
Some NO is removed from the system
A catalyst is added to the system
Le Chatelier’s Principle
Worksheet #4
Some CO was added to the system and a new equilibrium was established.
2CO (g) + O2 (g) ⇄ 2CO2 (g) + energy
1.
Compared to the original system, the rates of the forward and reverse reactions of the
new equilibrium. Forward Rate has
Reverse Rate has
2.
Compared to the original concentrations, after the shift, have the new concentrations
increased or decreased?
[CO]
[O2]
[CO2]
3.
Did the equilibrium shift favour the formation of reactants or products?
A catalyst was added to the system at constant volume and a new equilibrium was
established.
4.
2CO (g) + O2 (g) ⇄ 2CO2 (g) + energy
Compared to the original system, the rates of the forward and reverse reactions of the
new equilibrium. Forward Rate has
5.
Reverse Rate has
Compared to the original concentrations, after the shift, have the new concentrations
increased or decreased?
[CO]
6.
[O2]
[CO2]
Did the equilibrium shift favour the formation of reactants or products?
The volume of the container was decreased and a new equilibrium was established.
2CO (g) + O2 (g) ⇄ 2CO2 (g) + energy
7.
Compare to the original system, the rates of the forward and reverse reactions of the new
equilibrium. Forward Rate has
8.
Reverse Rate has
Compared to the original concentrations, after the shift, have the new concentrations
increased or decreased?
[CO]
9.
[O2]
[CO2]
Did the equilibrium shift favor the formation of reactants or products?
Worksheet #5 Applying Le Châtelier's Principle
1.
The chromate and dichromate ions set up an equilibrium system as follows:
energy + 2 CrO4 2-(aq) + 2 H+(aq) ⇄
yellow
Cr2O7 2-(aq) + H2O (l)
orange
Describe how the above equilibrium will shift after each stress below:
shift
color change
Increase in [H+]
Increase in [CrO4 2-]
Increase in [Cr2O7 2-]
Decrease in [H+]
Decrease in [CrO4 2-]
Increase in temperature
Decrease in temperature
Add HCl (aq)
Add NaOH
2.
The copper (II) ion and copper (II) hydroxide complex exist in equilibrium as follows:
Cu(OH)2 (aq) + 4 H2O (l)
violet
⇄
Cu(H2O)4 2+(aq) + 2 OH-(aq) + 215 kJ
light blue
Describe how the above equilibrium will shift after each stress below:
shift
Increase in [Cu(H2O)4 2+]
Add NaOH
Increase in [Cu(OH)2]
Decrease in [Cu(H2O)4 2+]
Decrease in [Cu(OH)2]
Increase temperature
Decrease temperature
Add KCl (aq)
Add HCl (aq)
color change
3.
Consider the equilibrium that follows:
4 HCl (g) + 2 O2 (g) ⇄
(clear)
2 H2O (l) +
2 Cl2 (g) +
(yellow)
98 kJ
Describe how the above equilibrium will shift after each stress below:
shift
color change
Increase in temperature
Increase [HCl]
Decrease in [Cl2]
Decrease temperature
Add Ne at constant volume
4.
Consider the equilibrium that follows:
Cu+ (aq) + Cl-(aq) ⇄ CuCl (s)
(green)
ΔH = + 98 kJ
Describe how the above equilibrium will shift after each stress below:
Cu+ is green
shift
color change
Increase in temperature
Increase [HCl]
Add NaCl
Decrease temperature
Add NaOH (aq)
(check your solubility table for a possible reaction)
Add CuCl(s)
Add AgNO3 (aq)
(check your solubility table for a possible reaction)
Add CuNO3 (aq)
Add Cu(NO3)2 (aq)
Worksheet #6
Graphing and LeChatelier’s Principle
Consider the following equilibrium system.
I2(g)
+
Cl2(g) ⇄ 2 ICl (g) + energy
Label the graph that best represents each of the following stresses and shift.

adding I2(g)

increasing the temperature

increasing the volume

removing Cl2(g)
I2
I2
ICl
ICl
I2
I2
ICl
Cl2
Worksheet #7 Maximizing Yield
1.
N2O4(g)
+ 59 KJ
⇄
2 NO2(g)
Describe four ways of increasing the yield of for the reaction above.
Describe three ways to increase the rate of the above reaction.
2.
2SO3(g)
⇄
2SO2(g)
+ O2(g)
+
215 KJ
Describe four ways of increasing the yield of for the reaction above.
Describe three ways to increase the rate of the above reaction.
3.
H2O(g) ⇄
H2O(l)
H = -150 KJ
Describe three ways of increasing the yield of for the reaction above.
Describe four ways to increase the rate of the above reaction.
4.
In the Haber reaction:
3H2(g) + N2(g) ⇌
2NH3(g)
+
Explain why each condition is used in the process to make ammonia.
A High pressure of 50 MP
The presence of Ur or Os
Condensing NH3 to a liquid
A relatively high temperature 500 oC
energy
Worksheet #8
1.
SO3(g)
Equilibrium Calculations
+
H2O(g)
⇄
H2SO4(l)
At equilibrium [SO3] = 0.400M
[H2O] = 0.480M
Calculate the value of the equilibrium constant.
2.
At equilibrium at 100oC, a 2.0L flask contains:
0.075 mol of PCl5
0.050 mol of H2O 0.750 mol of HCl
Calculate the Keq for the reaction:
[H2SO4] = 0.600M
0.500 mol of POCl3
PCl5 (s) + H2O (g) ⇄ 2HCl (g) + POCl3 (g)
3.
Keq= 798 at 25oC for the reaction: 2SO2 (g) + O2 (g) ⇄ 2SO3 (g).
In a particular mixture at equilibrium, [SO2]= 4.20 M and [SO3]=11.0M. Calculate the
equilibrium [O2] in this mixture at 25oC.
4.
Consider the following equilibrium:
2SO2 (g) + O2 (g) ⇄ 2SO3 (g)
0.600 moles of SO2 and 0.600 moles of O2 are present in a 4.00 L flask at equilibrium at
100oC. If the Keq = 680.0, calculate the SO3 concentration at 100oC.
5.
Consider the following equilibrium:
2 NO2(g)
⇄
N2O4(g)
2.00 moles of NO2 and1.60 moles of N2O4 are present in a 4.00 L flask at equilibrium at
20oC. Calculate the Keq at 20oC.
6.
2 SO3(g)
⇄
2 SO2(g)
+
O2(g)
4.00 moles of SO2 and 5.00 moles O2 are present in a 2.00 L container at 100oC and are at
equilibrium. Calculate the equilibrium concentration of SO3 and the number of moles
SO3 present if the Keq = 1.47 x 10-3.
7.
If at equilibrium [H2] = 0.200M and [I2] = 0.200M and Keq=55.6 at 250oC, calculate the
equilibrium concentration of HI.
H2 (g) + I2 (g) ⇄ 2HI (g)
8.
1.60 moles CO, 1.60 moles H2O, 4.00 moles CO2, 4.00 moles H2 are found in an 8.00 L
container at 690oC at equilibrium.
CO (g) + H2O (g) ⇄ CO2 (g) + H2 (g)
Calculate the value of the equilibrium constant.
Worksheet #9
Equilibrium Calculations
Solve each problem and show all of your work.
1.
At equilibrium, a 5.0L flask contains:
0.75 mol of PCl5
0.50 mol of H2O
Calculate the Keq for the reaction:
7.50 mol of HCl
5.00 mol of POCl3
PCl5 (s) + H2O (g) ⇄ 2HCl (g) + POCl3 (g)
2.
Keq= 798 for the reaction: 2SO2 (g) + O2 (g) ⇄ 2SO3 (g).
In a particular mixture at equilibrium, [SO2]= 4.20 M and [SO3]=11.0 M. Calculate the
equilibrium [O2] in this mixture.
3.
Consider the following equilibrium:
2SO2 (g) + O2 (g) ⇄ 2SO3 (g)
When 0.600 moles of SO2 and 0.600 moles of O2 are placed into a 1.00 litre container
and allowed to reach equilibrium, the equilibrium [SO3] is to be 0.250 M. Calculate the
Keq value.
4.
Consider the following equilibrium: 2 NO2(g)
⇄
N2O4(g)
2.00 moles of NO2 are placed in a 1.00 L flask and allowed to react. At equilibrium 1.80
moles NO2 are present. Calculate the Keq.
5.
2 SO2(g)
+
O2(g) ⇄
2 SO3(g)
4.00 moles of SO2 and 5.00 moles O2 are placed in a 2.00 L container at 200oC and
allowed to reach equilibrium. If the equilibrium concentration of O2 is 2.00 M, calculate
the Keq
6.
If the initial [H2] = 0.200 M, [I2] = 0.200 M and Keq = 55.6 at 250oC calculate the
equilibrium concentrations of all molecules.
H2 (g) + I2 (g) ⇄ 2HI (g)
7.
1.60 moles CO and 1.60 moles H2O are placed in a 2.00 L container at 690 oC
(Keq = 10.0).
CO (g) + H2O (g) ⇄ CO2 (g) + H2 (g)
Calculate all equilibrium concentrations.
8.
SO3(g) + NO(g)
⇄ NO2(g) + SO2(g)
Keq = 0.800 at 100oC. If 4.00 moles of each reactant are placed in a 2.00L container,
calculate all equilibrium concentrations at 100oC.
9.
Consider the following equilibrium system:
2NO2(g) ⇌
Two sets of equilibrium data are listed for the same temperature.
N2O4
Container 1
2.00 L
0.12 moles NO2
0.16 moles N2O4
Container 2
5.00 L
0.26 moles NO2
? moles N2O4
Determine the number of moles N2O4 in the second container. Get a Keq from the first
container and use it for the second container.
Worksheet #10
Equilibrium Calculations
Solve each problem and show all of your work.
1.
At equilibrium, a 2.0 L flask contains:
0.200 mol of PCl5
0.30 mol of H2O
Calculate the Keq for the reaction:
PCl5
(g)
+ H2O
(g)
⇄ 2HCl
(g)
+ POCl3
0.60 mol of HCl
0.300 mol of POCl3
(g)
2.
Keq= 798 for the reaction: 2SO2 (g) + O2 (g) ⇄ 2SO3 (g).
In a particular mixture at equilibrium, [SO2] = 4.20 M and [SO3] = 11.0M. Calculate the
equilibrium [O2] in this mixture.
3.
Consider the following equilibrium:
2SO2 (g) + O2 (g) ⇄ 2SO3 (g)
When a 0.600 moles of SO2 and 0.600 moles of O2 are placed into a 2.00 litre container
and allowed to reach equilibrium, the equilibrium [SO3] is to be 0.250 M. Calculate the
Keq value.
4.
H2(g) + S(s) ⇄
H2S(g) Keq= 14
0.60 moles of H2 and 1.4 moles of S are placed into a 2.0L flask and allowed to reach
equilibrium. Calculate the [H2] at equilibrium.
5.
Keq = 0.0183 for the reaction:
2HI(g) ⇄ H2(g) + I2(g)
If 3.0 moles of HI are placed in a 5.00L vessel and allowed to reach equilibrium, what is
the equilibrium concentration of H2?
6.
Consider the equilibrium:
I2 (g) + Cl2
(g)
⇄ 2ICl (g)
Keq= 10.0
The same number of moles of I2 and Cl2 are placed in a 1.0L flask and allowed to reach
equilibrium. If the equilibrium concentration of ICl is 0.040 M, calculate the initial
number of moles of I2 and Cl2.
7.
Consider the equilibrium:
2ICl(g) ⇄ I2 (g) + Cl2 (g) Keq= 10.0
If x moles of ICl were placed in a 5.0 L container at 10 oC and if an equilibrium
concentration of I2 was found to be 0.60 M, calculate the number of moles ICl initially
present.
8.
A student places 2.00 moles SO3 in a 1.00 L flask. At equilibrium [O2] = 0.10 M at
130 oC. Calculate the Keq.
Worksheet #11
2SO2(g) + O2(g) ⇄ 2SO3(g)
Review, Ktrial, & Size of Keq
1.
2 CrO4-2 (aq) + 2H+ (aq) ⇄ Cr2O7-2 (aq) + H2O (l)
Calculate the Keq if the following amounts were found at equilibrium in a 2.0L volume.
CrO4-2 = .030 mol, H+ = .020 mol, Cr2O7-2 = 0.32 mol, H2O = 110 mol
2.
PCl5(s) + H2O(g) ⇄ 2HCl (g) + POCl3 (g) Keq= 11
At equilibrium the 4.0L flask contains the indicated amounts of the three chemicals.
PCl5 0.012 mol
H2O 0.016 mol
HCl 0.120 mol
Calculate [POCl3].
3.
6.0 moles H2S are placed in a 2.0 L container. At equilibrium 5.0 moles H2 are present.
Calculate the Keq
4.
2H2S(g) ⇄ 2H2(g) + S2(g)
4.0 moles H2 and 2.0 moles Br2 are placed in a 1.0L container at 180oC. If the
[HBr] = 3.0 M at equilibrium, calculate the Keq.
H2(g) + Br2(g) ⇄ 2HBr(g)
5.
At 2000 0C Keq = 11.6 for: 2NO(g) ⇄ N2(g) + O2(g). If some NO was placed in a
2.0 L vessel, and the equilibrium [N2] = 0.120 M, calculate all other equilibrium
concentrations.
6.
At 800oC, Keq= 0.279 for CO2(g) + H2(g) ⇄ CO(g) + H2O(g).
If 2.00 moles CO( g) and 2.00 moles H2O (g) are placed in a 500.0 mL container, calculate
all equilibrium concentrations.
7.
CO(g) + H2O(g) ⇄ CO2(g) + H2(g)
Keq= 10.0 at 690oC.
If at a certain time
[CO] = 0.80 M, [H2O] = 0.050 M, [CO2] = 0.50 M and [H2] = 0.40 M, is the reaction at
equilibrium? If not, how will it shift in order to get to equilibrium
8.
For the reaction: CO(g) + H2O(g) ⇄ CO2(g) + H2(g)
Keq= 10.0 at 690 oC. The following
concentrations were observed: [CO]=2.0 M, [H2]= 1.0 M, [CO2]=2.0 M, [H2O] = 0.10 M.
Is the reaction at equilibrium? If not, how will it shift in order to get to equilibrium?
9.
For the equation below, the following concentrations were observed: [CO] = 1.5 M,
[H2] = 1.2 M, [CO2] = 1.0 M, [H2O] = 0.10 M. Is the reaction at equilibrium? If not, how
will it shift in order to get to equilibrium?
CO (g) + H2O (g) ⇄ CO2 (g) + H2 (g)
Keq= 10.0 at 690oC
10.
At a certain temperature the Keq for a reaction is 75. 2O3(g) ⇄ 3O2(g)
Predict the direction in which the equilibrium will proceed, if any, when the following
amounts are introduced to a 10 L vessel.
a) 0.60 mole of O3 and 3.0 mol of O2
b) 0.050 mole of O3 and 7.0 mol of O2
c) 1.5 mole of O3 and no O2
11)
Consider the following equilibrium:
a) 2NO2 (g) ⇄ N2O4 (g)
b) Cu
2+
(aq)
Keq = 2.2
+ 2Ag(s) ⇄ Cu(s) + 2Ag
+
c) Pb2+ (aq) + 2 Cl- (aq) ⇄
d) SO2(g) + O2 (g) ⇄
i)
ii)
(aq)
PbCl2(s)
SO3 (g)
Keq = 1 x 10-15
Keq = 6.3 x 104
Keq = 110
Which equilibrium favors products to the greatest extent?
Which equilibrium favors reactants to the greatest extent?
______
______
12.
What is the only way to change the value of the Keq?
13.
In the reaction: A + B ⇄ C + D + 100 kJ, what happens to the value of Keq if we
increase the temperature?
14.
If the value of Keq decreases when we decrease the temperature, is the reaction
exothermic or endothermic?
15.
In the reaction; W + X + 100kJ ⇄ Y + Z, what happens to the value of Keq if we
increase the (X)? Explain your answer.
16.
If the value of Keq increases when we decrease the temperature, is the reaction
exothermic or endothermic?
17.
Predict whether reactants of products are favored in the following equilibrium systems
18.
(a)
CH3COOH(aq) ⇄ H+(aq) + CH3COO-(aq)
Keq = 1.8 x 10-5
(b)
H2O2(aq) ⇄ H+(aq) + HO2(aq)
Keq = 2.6 x 10-12
(c)
CuSO4(aq) (+ Zn(s) ⇄ Cu(s) + ZnSO4(aq)
Keq = 1037
What effect will each of the following have on the Keq of the reaction shown below?
2NO2(g) + heat ⇄ N2O4(g)
(a)
(b)
(c)
(d)
(e)
(f)
(g)
Keq = 2.2
adding a catalyst
increasing the concentration of a reactant
increasing the concentration of a product
decreasing the volume
decreasing the pressure
increasing the temperature
decreasing the temperature
Worksheet #12
Enthalpy & Entropy
For each of these processes, predict if Entropy increases or decreases.
⇄
1.
2H2(g) + O2(g)
2H2O(g)
2.
2SO3(g)
⇄
3.
Ag+(aq)
+
4.
Cl2(g) ⇄
2Cl(g)
5.
H2O(l) ⇄
H2O(g)
6.
CaCO3(s)
+ 180 kJ ⇄ CaO(s)
7.
I2(s)
8.
4Fe(s)
2SO2(g)
Cl-(aq)
+ 608 kJ ⇄
+ 3O2(g) ⇄
+ O2(g)
⇄ AgCl(s)
+ CO2(g)
I2(aq)
2Fe2O3(s) + 1570 kJ
Consider both Enthalpy and Entropy and determine if each reaction will
a) go to completion
b) not occur or
c) go to equilibrium
9.
H2O(l) ⇄
10.
CaCO3(s)
11.
I2(s)
12.
4Fe(s) + 3O2(g) ⇄ 2Fe2O3(s) ∆H = +1570 kJ
⇄
H2O(g)
H = 150 kJ
+ 180 kJ ⇄ CaO(s)
I2(aq)
+ CO2(g)
+ 608 kJ
13.
Cl2(g) ⇄
14.
Ag+(aq) + Cl-(aq) ⇄ AgCl(s) + 86.2 kJ
H = +26.8 kJ
2Cl(g)
Consider both Enthalpy and Entropy and determine if each reaction will
a) have a large Keq
b) have a small Keq
c) have a Keq about equal to 1
15.
H2SO4(aq) + Zn(s) ⇄ ZnSO4(aq) + H2(g)
H = +207 kJ
16.
NH4NO3(s) ⇄
H = -30 kJ
17.
N2(g) + 3H2(g) + 92 kJ ⇄
18.
H2O(l) + 150 kJ ⇄
19.
Ca(s)
NH4+(aq)
+ NO3-(aq)
2NH3(g)
H2O(g)
+ H2O(l) ⇄ Ca(OH)2(aq)
+
H2(g)
H = +210 kJ
Equilibrium
Quiz # 1
Approaching Equilibrium
1.
Consider the following equilibrium: H2O(g) + CO(g) ⇄ H2(g) + CO2(g)
A closed container is initially filled with H2O and CO. As the reaction proceeds towards equilibrium the
A.
[CO] and [CO2] both increase
B.
[ CO] and [CO2] both decrease
C.
[CO] increases and [CO2] decreases
D.
[CO] decreases and [CO2] increases
2.
Consider the following equilibrium: 2SO3(g) ⇄ 2SO2(g) + O2(g)
At equilibrium, the rate of decomposition of SO3
A.
Equals the rate of formation of O2
B.
Equals the rate of formation of SO3
C.
Is less than the rate of formation of O2
D.
Is less than the rate of formation of SO3
3.
Which of the following is true for all equilibrium systems?
A.
The mass of reactants is equal to the mass of products
B.
Addition of a catalyst changes the equilibrium concentrations
C.
The concentration of reactants is equal to the concentration of products
D.
The rate of the forward reaction is equal to the rate of the reverse reaction
4.
Consider the following: 2NH3(g) ⇄
N2(g) + 3H2(g)
A flask is initially filled with NH3. As the system approaches equilibrium, the rate of the forward reaction
A.
Increases as the rate of the reverse reaction decreases
B.
Decreases as the rate of the reverse reaction increases
C.
Increases as the rate of the reverse reaction increases
D.
Decreases as the rate of the reverse reaction decreases
5.
A system at equilibrium is said to be dynamic because at equilibrium the
A.
Temperature does not change
B.
Macroscopic properties are constant
C.
Forward and reverse reactions continue to occur
D.
Concentrations of reactants and products are constant
6.
In all systems at equilibrium, the
A.
Concentration of reactants is less than the concentration of products
B.
Concentration of reactants and the concentration of products are equal
C.
Concentration of reactants is greater than the concentration of products
D.
Concentration of reactants and the concentration of products are constant
7.
Consider the following equilibrium: H2O(g) + CO(g) ⇄
H2(g) + CO2(g)
At high temperature, H2O and CO are placed in a closed container. As the system approaches equilibrium,
the
A.
Rate of the forward and reverse reaction both increase
B.
Rate of the forward and reverse reaction both decrease
C.
Rate of the forward reaction decreases and the rate of the reverse reaction increases
D.
Rate of the forward reaction increases and the rate of the reverse reaction decreases
8.
Which of the following statements are true for all equilibrium systems?
I.
Macroscopic Properties are constant
II.
Mass of the reactants equals mass of the products
III
Equilibrium can be achieved from either products or reactants
A.
I and II only
B.
I and III only
C.
II and III only
D.
I, II, and III
9.
Consider the following equilibrium: N2O4(g) + heat ⇄
2NO2(g)
Initially, a 1.0 L container is filled with 2.0 mol of NO 2. As the system approaches equilibrium, the rate of
reaction of NO2
A.
Increases and [ N2O4 ] increases
B.
Increases and [ N2O4 ] decreases
C.
Decreases and [ N2O4 ] increases
D.
Decreases and [ N2O4 ] decreases
10.
Consider the following equilibrium: N2(g) + O2(g) ⇄
2NO(g)
Nitrogen gas and oxygen react when placed in a closed container. As the reaction proceeds towards
equilibrium, the rate of the reverse reaction
A.
Increases as the concentration of products decreases
B.
Decreases as the concentration of products decreases
C.
Increases as the concentration of products increases
D.
Decreases as the concentration of products increases
11.
Consider the following
I
II
III
Constant Temperature
Equal concentrations of reactants and products
Equal rates of forward and reverse reactions
A system at equilibrium must have
A.
I and II only
B.
I and III only
C.
II and III only
D.
I, II , and III
N2O4(g)
⇌
2NO2(g)
Colourless
Brown
NO2 is placed in a flask at a constant temperature. Which of the following is true as the system approaches
equilibrium?
A.
The colour gets darker as [NO2] increases.
B.
The colour gets lighter as [NO2] decreases.
C.
The colour gets darker as [N2O4] increases.
D.
The colour gets lighter as [N2O4] decreases.
12.
Consider the following:
13.
Consider the following:
N2O4(g)
Colourless
⇌
2NO2(g)
Brown
N2O4 is placed in a flask at a constant temperature. Which of the following is true as the system approaches
equilibrium?
A.
The colour gets darker as [NO2] increases.
B.
The colour gets lighter as [NO2] decreases.
C.
The colour gets darker as [N2O4] increases.
D.
The colour gets lighter as [N2O4] decreases.
14.
Consider the following equilibrium:
PCl3(g) + Cl2(g) ⇌
PCl5(g)
If PCl5 is put in a container, how will the reaction rates change as the system approaches equilibrium?
Forward Rate
Reverse Rate
A.
increases
increases
B.
increases
decreases
C.
decreases
decreases
D.
decreases
increases
15.
Consider the following equilibrium system: H2O(g) + CO(g) ⇌ CO2(g) + H2(g)
2.00 mole of CO2 and 2.00 mole of H2 are placed in a container and the system approached equilibrium.
The following changes occur:
A.
B.
C.
D.
[CO2]
increases
increases
decreases
decreases
[H2]
decreases
increases
increases
decreases
[CO]
decreases
decreases
increases
increases
16.
For the equilibrium system below:
Zn(s) + CuSO4(aq)  Cu(s) + ZnSO4(aq)
We would know the system is at equilibrium because:
A.
[Cu2+]
= [Zn2+]
B.
Cu(s)
= Zn(s)
C.
the mass of Cu(s) remains constant.
D.
the mass of the entire system remains constant.
17.
Which of the factors below is not a condition necessary for equilibrium?
A.
a closed system
B.
a constant temperature
C.
equal forward and reverse reaction rates
D.
equal concentrations of reactants and products
18.
Products are placed in a beaker. How do the rates of the forward and reverse reactions change as the
system proceeds to equilibrium?
Forward Rate
Reverse Rate
A.
increases
increases
B.
increases
decreases
C.
decreases
increases
D.
decreases
decreases
19.
Which of the factors below is not a condition necessary for equilibrium?
A.
constant macroscopic properties
B.
constant concentrations of reactant and product
C.
equal forward and reverse reaction rates
D.
a high activation energy
Equilibrium Quiz #2
1.
LeChatelier’s Principle
Consider the following reaction: 2SO2(g) + O2(g) ⇄ 2SO3(g) ∆H = -197 kJ/mol
Which of the following will not shift the equilibrium to the right?
A.
Adding more O2
B.
Adding a catalyst
C.
Increasing the pressure
D.
Lowing the temperature
2.
Consider the following equilibrium system: CaCO3(s) ⇄ CaO(s) + CO2(g)
Which one of the following changes would cause the above system to shift left?
A.
Add more CaO
B.
Remove CaCO3
C.
Decrease volume
D.
Increase surface area of CaO
3.
Consider the following equilibrium: SO2Cl2(g) + energy ⇄ SO2(g) + Cl2(g)
When the temperature is decreased, the equilibrium shifts
A.
Left and [ SO2Cl2 ] increases
B.
Left and [ SO2Cl2 ] decreases
C.
Right and [ SO2Cl2 ] increases
D.
Right and [ SO2Cl2 ] increases
4.
Consider the following equilibrium: 2SO3(g) ⇄ 2SO2(g) + O2(g)
The volume of the system is decreased at a constant temperature. A new state of equilibrium is established
by a shift of the original equilibrium to the
A. Left and [SO3] increases
B. Right and [SO3] decreases
C. Left and [SO3] remains unchanged
D. Right and [SO3] remains unchanged
5.
Consider the following equilibrium system: CO2(g) + H2(g) ⇄ CO(g) + H2O(g)
Which of the following, when added to the system above, would result in a net decrease in [H2O]?
A. CO2
B. H2
C. CO
D. H2
6.
Consider the following equilibrium: C(s) + 2H2(g) ⇄ CH4(g) + 74 kJ
When a small amount of solid C is added to the system
A. [H2] decreases
B. [CH4] increases
C. The temperature increases
D. All concentrations remain constant
7.
Consider the following equilibrium: 2NO(g) + Cl2(g) ⇄ 2NOCl(g)
At constant temperature and volume, Cl2 is added to the above equilibrium system. As equilibrium reestablishes, the
A. [NOCl] will decrease
B. The temperature increases
C. [NO] will increase
D. [NOCl] will increase
8.
Consider the following equilibrium: Cl2O7(g) +8H2(g) ⇄ 2HCl(g) + 7H2O(g)
Which of the following would increase the number of moles of HCl?
A. Increase [H2O]
B. Increase [Cl2O7]
C. Increase total pressure
D. Increase volume of the system
9.
Consider the following equilibrium: 2HI(g) ⇄
H2(g) + I2(g) ∆H = -68kJ
Which of the following would cause the equilibrium to shift right?
A. Increasing the volume
B. Decreasing the volume
C. Increasing the temperature
D. Decreasing the temperature
10.
A 1.00 L flask contains a gaseous equilibrium system. The addition of reactants to this flask results in a
A. Shift to the left and decrease in the concentration of products
B. Shift to the left and increase in the concentration of products
C. Shift to the right and decrease in the concentration of products
D. Shift to the right and increase in the concentration of products
11.
When the temperature of an equilibrium system is increased, the equilibrium always shifts to favor the
A. Exothermic reaction
B. Endothermic reaction
C. Formation of products
D. Formation of reactants
12.
An equilibrium system shifts left when the
A. Rate of the forward reaction is equal to the rate of the reverse reaction
B. Rate of the forward reaction is less than the rate of the reverse reaction
C. Rate of the forward reaction is greater than the rate of the reverse reaction
A. Rate of the forward reaction and the rate of the reverse reaction are constant
13.
Consider the following equilibrium: 2SO2(g) + O2(g) ⇄ 2SO3(g)
There will be no shift in the equilibrium when
A. More O2 is added
B. Catalyst is added
C. The volume is increased
D. The temperature is increased
14.
Consider the following equilibrium: 2NOCl(g) ⇄ 2NO(g) + Cl2(g)
In a 1.0 L container at equilibrium there are 1.0 mol NOCl, 0.70 mol NO and 0.40 mol Cl 2. At constant
temperature and volume, 0.10 mol NOCl is added. The concentrations in the “new” equilibrium in
comparison to the concentrations in the “old” equilibrium are
A.
B.
C.
D.
15.
[NOCl]
new = old
new > old
new < old
new < old
[NO]
new = old
new > old
new < old
new > old
Consider the following equilibrium: N2O4(g) + 58 kJ ⇄ 2NO2(g)
The equilibrium shifts right when
A. NO2 is added
B. N2O4 is removed
C. The temperature is decreased
D. The volume of the system is increased
∆H = -198 kJ
[Cl2]
new = old
new > old
new > old
new > old
16.
Consider the following equilibrium: 2SO2(g) + O2(g) ⇄ 2SO 3(g)
Which of the following will shift the equilibrium to the right?
I. Adding more O2
II. Adding more SO3
III. Adding a catalyst
A. I only
B. III only
C. I and II only
D. II and III only
17.
Consider the following equilibrium:
energy + 2NaClO3(s) ⇌ 2NaCl(s) + 3O2(g)
Which of the following will cause a shift to the left?
A.
adding more O2
B.
adding more NaCl
C.
removing some NaClO3
D.
increasing the temperature
18.
Consider the following equilibrium:
CO(g) + 2H2(g) ⇌ CH3OH(g) + energy
Which of the factors below would decrease the concentration of CH 3OH at equilibrium?
A.
an addition of CO
B.
an increase in H2
C.
a decrease in the temperature
D.
an increase in the temperature
19.
Consider the following equilibrium:
energy + 2NaClO3(s) ⇌ 2NaCl(s) + 3O2(g)
Which of the following will cause a shift to the right?
A.
adding more O2
B.
adding more NaCl
C.
removing some NaCl(s)
D.
increasing the temperature
20.
Consider the following equilibrium: 2SO2(g) + O2(g) ⇄ 2SO 3(g)
Which of the following will shift the equilibrium to the left?
I. Removing O2
II. Adding more SO3
III. Adding a catalyst
A.
B.
C.
D.
I only
III only
I and II only
II and III only
21.
Consider the following equilibrium:
N2O4(g) + energy ⇌ 2NO2(g)
How are N2O4 and NO2 affected by the addition of He into the container at constant volume.
N2O4
NO2
A.
no change
no change
B.
no change
increases
C.
increases
decreases
D.
decreases
increases
22.
Which of the following stresses will cause a shift to the reactants?
23.
H2(g) + Br2(g) ⇌ 2HBr(g) + energy
A.
increase [Br2]
B.
increase [H2]
C.
decrease temperature
D.
increase temperature
Which of the following stresses will cause a shift to the products?
H2(g) + Br2(g) ⇌ 2HBr(g) + energy
A.
decrease [Br2]
B.
decrease [H2]
C.
decrease temperature
D.
increase temperature
24.
Which of the following two stresses will each cause the system to shift to the left?
2SO2(g)
A.
B.
C.
D.
+ O2(g) ⇄ 2SO 3(g) + energy
decrease temperature and decrease [O2]
increase temperature and increase [SO3]
increase temperature and decrease [SO3]
decrease temperature and increase [SO2]
25.
SrCO3(s) + 215 kJ ⇌ SrO(s) + CO2(g)
Which of the
following conditions would produce the greatest yield of SrO(s)?
Temperature
Pressure
A.
low
low
B.
low
high
C.
high
low
D.
high
high
26.
The Haber Process is used to produce ammonia commercially according to the following equilibrium:
N2(g) + 3H2(g) ⇌ 2NH3(g) + energy
Which of the following conditions will produce the highest yield of ammonia?
A.
increase temperature and increase pressure
B.
increase temperature and decrease pressure
C.
decrease temperature and increase pressure
D.
decrease temperature and decrease pressure
27.
Consider the following reaction: 2SO2(g) + O2(g) ⇄ 2SO3(g) ∆H = -197 kJ/mol
If the volume is increased what happens to position of the equilibrium?
A.
shifts to the right
B.
shifts to the left
C.
no shift
D.
shifts in the exothermic direction
28.
Consider the following reaction: 2NH3(g) + energy ⇄ N2(g) + 3H2(g)
If the volume is increased what happens to position of the equilibrium?
A.
shifts to the right
B.
shifts to the left
C.
no shift
D.
shifts in the exothermic direction
29.
Consider the following reaction: SrCO3(s) + 215 kJ ⇌ SrO(s) + CO2(g)
If the volume is decreased what happens to position of the equilibrium?
A.
shifts to the right
B.
shifts to the left
C.
no shift
D.
shifts in the exothermic direction
30.
Consider the following reaction: H2(g) + Br2(g) ⇌ 2HBr(g) + energy
If the volume is increased what happens to position of the equilibrium?
A.
shifts to the right
B.
shifts to the left
C.
no shift
D.
shifts in the exothermic direction
31.
Consider the following reaction: N2O4(g) + energy ⇌ 2NO2(g)
If the volume is decreased what happens to position of the equilibrium?
A.
shifts to the right
B.
shifts to the left
C.
no shift
D.
shifts in the exothermic direction
Quiz # 3
Yield/Graphing/LeChatelier’s Principle
1.
When a catalyst is added to an equilibrium system, the forward reaction
A.
Increases and the reverse decreases
B.
Decreases and the reverse decreases
C.
Decreases and the reverse increases
D.
Increases and the reverse increases
2.
Consider the following concentration versus time graph for the equilibrium
⇄
N2O4(g)
2NO2(g)
Concentration
“t”
TIME(S)
At time= “t”, which one of the following stresses occurred
A.
Catalyst was added
B.
Pressure was changed
C.
Temperature was changed
D.
Concentration of NO2 was changed
3.
4.
Which of the following reactions will shift left when pressure is increased and when temperature is
decreased?
A.
N2(g) + 2O2(g) + heat
B.
N2(g) + 3H2(g)
C.
CH4(g) + H2O(g) + heat
D.
CS2(g) + 4H2(g)
⇄
⇄
⇄
2NO2(g)
2NH3(g) + heat
⇄
CO(g) + 3H2(g)
CH4(g) + 2H2S(g) + heat
Consider the following graph, which relates to this equilibrium
⇄
N2(g) + 3H2(g)
2NH3(g)
∆H = -92kJ
[NH3]
[H2]
[]
[N2]
Time
Which of the following caused the changes in the concentrations at time t ?
A.
Addition of N2
B.
Removal of H2
C.
Decrease in temperature
D.
Decrease in reaction volume
5.
Consider the following equilibrium: CH4(g) + H2O(g) + heat ⇄ CO(g) + 3H2(g)
In which of the following will both stresses shift the equilibrium right
A.
A decrease in temperature and a decrease in volume
B.
An increase in temperature and a decrease in volume
C.
A decrease in temperature and an increase in volume
D.
An increase in temperature and an increase in volume
6.
Consider the following equilibrium system: N2(g) + 3H2(g) ⇄
2NH3(g) + 92 kJ
In order to maximize the yield for this reaction, the best conditions are:
A. Low pressure and low temperature
B. Low pressure and high temperature
C. High temperature and low pressure
D. High pressure and low temperature
7.
Consider the following equilibrium system: NH3(aq) + H2O(l) ⇄ NH+4(aq) + OH--(aq)
Which of the following when added to the above equilibrium system would cause an increase in [OH-]
A. NH3
B. H2O
C. NH4+
D. HCl
8.
Consider the following reversible reaction: Fe3+(aq) + SCN-(aq) ⇄ FeSCN2+(aq)
A solution of Fe(NO3)3 is added to a solution of KSCN. Which one of the following statements describes
the changes in forward and reverse reaction rates as the reaction moves towards equilibrium?
A.
Forward and reverse rates increase
B.
Forward and reverse rates decrease
C.
Forward rate increases and reverse rate decrease
D.
Forward rate decreases and reverse rate increase
9.
Consider the following equilibrium: N2(g) + O2(g) ⇄ 2NO(g)
When the temperature is decreased, the equilibrium
A. Shifts left and [NO] decreases
B. Shifts left and [NO] increases
C. Shifts right and [NO] increases
D. Shifts right and [NO] decreases
10.
Consider the following equilibrium: N2(g) + 3H2(g) ⇄
2NH3(g) + 92 kJ
In which of the following will both changes shift the equilibrium right?
A. An increase in volume and a decrease in temperature
B. An increase in volume and a increase in temperature
C. A decrease in volume and a decrease in temperature
D. A decrease in volume and an increase in temperature
11.
Consider the following equilibrium: CaCO3(s) + 556 kJ
The equilibrium will shift to the right
A. CO2 is added
B. CaCO3(s) is added
C. The temperature is increased
D. The temperature is decreased
12.
Consider the following equilibrium: SO2(g) + NO2(g) ⇄ SO3(g) + NO(g) + energy
The equilibrium does not shift with a change in the
A. Volume
B. Temperature
C. Concentration of products
D. Concentration of reactants
13.
Consider the following equilibrium: 2Hl(g)
⇄
H2(g) + I2(g)
At constant temperature and volume, more I2 is added to the above equilibrium. A new state of equilibrium
results from a shift to the
A. Left with a net decrease in [H2]
B. Left with a net increase in [H2]
C. Right with a net increase in [H2]
D. Right with a net decrease in [H2]
⇄
∆H= + 181 kJ
CaCO(s) + CO2(g)
14.
Consider the following diagram for the equilibrium system:
Energy +
N2O4(g)
⇄
2NO2(g)
[N2O4]
Concentration
[NO2]
A.
B.
C.
D.
15.
[NO2] was increased.
[N2O4] was decreased.
Temperature was increased.
Temperature was decreased.
Consider the following diagram for the equilibrium system:
Energy +
N2O4(g)
⇄
2NO2(g)
[N2O4]
Concentration
[NO2]
A.
B.
C.
D.
16.
[NO2] was increased.
[N2O4] was decreased.
Temperature was increased.
Temperature was decreased.
Consider the following diagram for the equilibrium system:
Energy +
N2O4(g)
⇄
[N2O4]
Concentration
[NO2]
A.
B.
C.
D.
[NO2] was increased.
[N2O4] was decreased.
Temperature was increased.
The Volume was decreased.
2NO2(g)
17.
Which of the following describes the temperature and pressure needed for the maximum yield of NO2?
Energy + N2O4(g)
Temperature
A.
low
B.
low
C.
high
D.
high
18.
⇄
2NO2(g)
Pressure
low
high
low
high
Which of the following describes the temperature and pressure needed for the maximum yield of NH3?
N2(g) + 3H2(g) ⇄
2NH3(g) + 92 kJ
Temperature
Pressure
A.
low
low
B.
low
high
C.
high
low
D.
high
high
19.
Which of the following describes the temperature and pressure needed for the maximum yield of CO2?
CaCO3(s) ⇄ CaCO(s) + CO2(g)
Temperature
A.
low
B.
low
C.
high
D.
high
20.
ΔH = +215 kJ
Pressure
low
high
low
high
Consider the following equilibrium: CaCO3(s) ⇌ CaO(s) + CO2(g) ΔH = +160 kJ
Which starting materials could establish an equilibrium?
1
CaCO3(s)
2
CaO(s)
3
CaO(s) and CO2(g)
4
CaCO3(s) and CO2(g)
A.
1, 2, 3 only
B.
1, 2, 4 only
C.
1, 3, 4 only
D.
3, 4 only
Consider the following reaction for the next five questions 21 to 25.
4NH3(g) + 3O2(g) ⇌ 2N2(g) + 6H2O(l) + 1250 kJ
21.
Which of the following would cause the concentration of NH3 at equilibrium to increase?
A.
an increase in [O2]
B.
a increase in volume
C.
a decrease in temperature
D.
an increase in temperature
22.
What happens when NH3 is added to the above system?
Equilibrium
[N2]
A.
no shift
unchanged
B.
shifts right
decreases
C.
shifts right
increases
D.
shifts left
increases
23.
If some O2 is removed from the system, what happens to the forward and reverse reaction rates after
equilibrium is re-established?
Forward Reaction Rate
Reverse Reaction Rate
A.
increases
decreases
B.
decreases
decreases
C.
increases
increases
D.
decreases
increases
24.
If some O2 is injected into the system, what happens to the forward and reverse reaction rates during the
shift to re-establish equilibrium?
Forward Reaction Rate
Reverse Reaction Rate
A.
increases
decreases
B.
decreases
decreases
C.
increases
increases
D.
decreases
increases
25.
Consider the equilibrium: N2(g) + 3H2(g) ⇄
2NH3(g) + 92 kJ
The following diagram represents the rate of the reverse reaction.
t1
Which of the following stresses explains what happened at t1 ?
A.
[H2] increased.
B.
[N2] decreased.
C.
[NH3] increased.
D.
[NH3] decreased.
26.
Consider the equilibrium: N2(g) + 3H2(g) ⇄
2NH3(g) + 92 kJ
The following diagram represents the rate of the forward reaction.
t1
Which of the following stresses explains what happened at t1 ?
A.
[H2] increased.
B.
temperature was lowered
C.
[NH3] increased.
D.
[NH3] decreased.
27.
Consider the equilibrium: N2(g) + 3H2(g) ⇄
2NH3(g) + 92 kJ
The following diagram represents the rate of the reverse reaction.
t1
Which of the following stresses explains what happened at t1 ?
A.
[H2] increased.
B.
[N2] decreased.
C.
[NH3] increased.
D.
[NH3] decreased.
28.
A small amount of NaOH is added to the following equilibrium system:
2CrO42- + 2H+ ⇌ Cr2O72-(aq)
+ H2O(l)
How do the [CrO42-] and the reverse reaction rate change as equilibrium is re-established?
[CrO42-] Reverse Rate
A.
increases
increases
B.
increases
decreases
C.
decreases
decreases
D.
decreases
increases
29.
A small amount of H2SO4 is added to the following equilibrium system:
2CrO42- + 2H+ ⇌ Cr2O72-(aq)
+ H2O(l)
How do the [CrO42-] and the reverse reaction rate change as equilibrium is re-established?
[CrO42-] Reverse Rate
A.
increases
increases
B.
increases
decreases
C.
decreases
decreases
D.
decreases
increases
30.
A small amount of NaOH is added to the following equilibrium system:
2CrO42- + 2H+ ⇌ Cr2O72-(aq)
+ H2O(l)
How do the [Cr2O72-] and the reverse reaction rate change as equilibrium is re-established?
[Cr2O72-]Reverse Rate
A.
increases
increases
B.
increases
decreases
C.
decreases
decreases
D.
decreases
increases
31.
A small amount of H2SO4 is added to the following equilibrium system:
2CrO42- + 2H+ ⇌ Cr2O72-(aq)
+ H2O(l)
How do the [Cr2O72-] and the reverse reaction rate change as equilibrium is re-established?
[Cr2O72-]Reverse Rate
A.
increases
increases
B.
increases
decreases
C.
decreases
decreases
D.
decreases
increases
Quiz #4
1.
Writing and Calculating Keq
The equilibrium constant expression for the following reaction is:
2Hg(l) + O2(g) ⇄ 2HgO(s)
A.
Keq = 1/[O2]
B.
Keq = [O2]
C.
Keq = [2HgO] / [O2] [2Hg]
D.
Keq = [HgO]2 / [Hg]2[O2]
2.
Identify the equilibrium system that least favors the formation of products
⇄
2Hg(l) + O2(g)
Keq = 1.2 x 10-22
A.
2HgO(s)
B.
CH3COOH(aq) + H2O(l) ⇄ H3O+(aq) + CH3COO-(aq) Keq = 1.8 x 10-5
C.
2NO(g) + O2(g)
⇄
D.
H2(g) + Cl2(g)
⇄
2NO2(g)
2HCl(g)
Keq = 6.5 x 105
Keq = 1.8 x 1033
3.
Consider the following equilibrium system: 3O2(g) ⇄ 2O3(g) Keq = 1
Which equation compares the concentration of oxygen and ozone?
A.
[O2]
= [O3]2/3
B.
[O2]
= [O3]
C.
[O2]
= [O3]3/2
2/5
D.
[O2]
= [O3]
4.
For which of the following equilibrium does Keq = [O2]
5.
A.
O2(l)
⇄
O2(g)
B.
2O3(g)
⇄
3O2(g)
C.
2H2O(l)
D.
2Hg(s) + O2(g)
⇄
2H2(g) + O2(g)
⇄
2HgO(s)
Consider the following equilibrium system at 25O C :
2SO2(g) + O2(g) ⇄ 2SO3(g)
At equilibrium, [SO2] is 4.00 x 10-3 mol/L, [O2] = 4.00 x 10-3 mol/L and
[SO3] is 2.33 x 10-3 mol/L. From this data, the Keq value for the above system is
A.
B.
C.
D.
6.85 x 10-3
1.18 x 10-2
84.8
146
6.
Consider the following equilibrium system: PCl5(g) ⇄ PCl3(g) + Cl2(g)
At equilibrium, [PCl5] is a 0.400 M. [PCl3] is 1.50 M and [Cl2] is 0.600 M.
The Keq for the reaction is
A.
0.360
B.
0.444
C.
0.900
D.
2.25
7.
Consider the following equilibrium: 2H2S(g) ⇄ 2H2(g) + S2(g)
At equilibrium, [H2S] = 0.50 mol/L. [H2] = 0.10 mol/L and [S2] = 0.40 mol/L.
The value of Keq is calculated using the ratio
A
(0.10)(0.40)
(0.50)
B.
(0.10)2(0.40)
(0.50)2
C.
(0.50)
(0.10)(0.50)
D.
(0.50)2
(0.10)2(0.40)
8.
Consider the following equilibrium: 2NO(g) + Cl2(g) ⇄ 2NOCl(g)
Keq = 12
At equilibrium, [NOCl] = 1.60 mol/L and [NO] = 0.80 mol/L. The [Cl 2] is
A.
0.17 mol/L
B.
0.27 mol/L
C.
0.33 mol/L
D.
3.0 mol/L
9.
Consider the following equilibrium: I2(s) + H2O(l) ⇄ H+(aq) + I-(aq) + HOI(aq)
The equilibrium constant expression for the above system is
10.
A.
Keq = [H+][I-]
B.
Keq = [H+][I-][HOI]
C.
Keq = [H+][I-][HOI]
[I2][H2O]
D.
Keq = [H+][I-][HOI]
[H2O]
Consider the following equilibrium: 2CO(g) + O2(g) ⇄
The ratio used to calculate the equilibrium constant is
A.
[2CO]2[O2]
[2CO2]2
B.
[2CO2]2
[2CO]2[O2]
C.
[CO]2[O2]
[CO2]2
D.
[CO2]2
[CO]2[O2]
2CO2(g)
11.
Consider the following equilibrium: 2Fe(s) + 3H2O(g) ⇄ Fe2O3(s) + 3H2(g)
The equilibrium constant expression is
[Fe2O3][H2]3
[Fe]2[H2O]3
A.
Keq =
B.
Keq = [Fe2O3][3H2]
[2Fe] [3H2O]
C.
Keq = [H2]3
[H2O]3
D.
Keq = [H2]3
⇄
12.
Consider the following equilibrium: N2O4(g)
At equilibrium, the [N2O4] is equal to
A.
0.133
[NO2]
B.
[NO2]
0.133
C.
0.133
[NO2]2
D.
[NO2]2
0.133
2NO2(g)
Keq = 0.133
13.
Consider the following equilibrium: 4KO2(s) + 2H2O(g) ⇄
The equilibrium constant expression is
A.
Keq = [KOH]4[O2]3
[KO2]4[H2O]2
B.
Keq = [O2]3
[H2O]2
C.
Keq = [KO2]4[H2O]2
[KOH]4[O2]3
D.
Keq = [H2O]2
[O2]3
14.
Consider the following equilibrium: C(s) + H2O(g) ⇄ CO(g) + H2(g)
The contents of a 1.00 L container at equilibrium were analyzed and found to
contain 0.20 mol C, 0.20 mol H2O, 0.60 mol CO and 0.60 mol H2. The equilibrium constant is
A.
0.11
B.
0.56
C.
1.8
D.
9.0
15.
Consider the following equilibrium: N2O4(g) ⇄ 2NO2(g) Keq = 4.61 x 10-3
A 1.00 L container at equilibrium was analyzed and found to contain
0.0200 moles NO2. At equilibrium, the concentration of N2O4 is
A.
0.0868 mol/L
B.
0.230 mol/L
C.
4.34 mol/L
D.
11.5 mol/L
4KOH(s) + 3O2(g)
16.
Consider the following equilibrium: CH4(g) + H2O(g) ⇄ CO(g) + 3H2(g) Keq= 5.7
At equilibrium, the [CH4] = 0.40 mol/L [CO] = 0.30 mol/L and
[H2] = 0.80 mol/L. The [H2O] is
A.
0.067 mol/L
B.
0.11 mol/L
C.
2.2 mol/L
D.
5.3 mol/L
17.
Consider the following equilibrium: H2(g) + I2(g) ⇄ 2HI(g)
At equilibrium, the [H2] = 0.020 mol/L. [I2] = 0.020 mol/L
and [HI] = 0.160 mol/L. The value of the equilibrium constant is
A.
2.5 x 10-3
B.
1.6 x 10-2
C.
6.4 x 101
D.
4.0 x 102
18.
Consider the following constant expression: Keq = [CO2]. Which one of the following equilibrium systems
does the above expression represent?
⇄
A.
CO2(g)
B.
PbO(s) + CO2(g) ⇄
CO2(s)
C.
CaCO3(s)
⇄
CaO(s) + CO2(g)
D.
H2CO3(aq)
⇄
H2O(l) + CO2(aq)
PbCO3(s)
19.
Given the following equilibrium system: Br2(g)
⇄
The equilibrium constant expression for the above system is
A. Keq = [Br2(l)]
[Br2(g)]
B. Keq = [Br2(g)]
C. Keq =
1 __
[Br2(g)]
D. Keq = [Br2(g)] [Br2(g)]
20.
Consider the following equilibrium: CO(g) + 2H2(g) ⇄ CH3OH(g) + 91 kJ
A change in temperature of the above system increases the value of the equilibrium constant. The new state
of equilibrium was established by a shift
A.
Left as a result of a decrease in temperature
B.
Right as a result of a decrease in temperature
C.
Left as a result of an increase in temperature
D.
Right as a result of an increase in temperature
21.
Consider the equilibrium: SrCO3(s) ⇌ SrO(s) + CO2(g) In a 2.5 L container
at equilibrium there are 2.42 g CO2, 1.00 g SrCO3 and 1.00 SrO.
Which of the following is the value of Keq?
A.
0.022
B.
0.011
C.
0.020
D.
91
23.
Consider the following equilibrium:
CH4(g) + H2O(g) ⇌ CO(g) + 3H2(g)
At equilibrium, 1.20 mol CH4, 1.20 mol H2O, 0.080 mol CO and 0.040 mol H2
are present in a 2.0 L container. What is the value of Keq ?
A.
4.3 x 10-6
B.
2.2 x 10-2
C.
2.2 x 10-4
D.
8.9 x 10-7
Br2(l)
24.
Consider the following equilibrium: Cr2O72-(aq) + 2OH-(aq) ⇌ 2CrO42-(aq) + H2O(l)
The concentration of ions at equilibrium was measured at a specific temperature and found to be
[CrO42-] = 0.100 M, [Cr2O72-] = 0.20 M, and [OH-] = 0.11 M.
What is the Keq?
A.
41
B.
4.13
C.
0.83
D.
0.11
25.
Consider the following equilibrium:Cr2O72-(aq) + 2OH-(aq) ⇌ 2CrO42-(aq) + H2O(l)
Keq = 4.14
The concentration of ions at equilibrium was measured at a
specific temperature and found to be
[Cr2O72-] = 0.100 M and [OH-] = 0.20 M. What is the equilibrium [CrO42-]?
A.
0.017 M
B.
0.083 M
C.
0.13 M
D.
0.32 M
26.
Consider the following equilibrium:Cr2O72-(aq) + 2OH-(aq) ⇌ 2CrO42-(aq) + H2O(l)
Keq = 4.14
The concentration of ions at equilibrium was measured at a
specific temperature and found to be
[CrO42-] = 0.100 M and [OH-] = 0.20 M. What is the equilibrium [Cr2O72-]?
A.
0.060 M
B.
0.083 M
C.
0.13 M
D.
0.32 M
27.
Consider the following equilibrium:Cr2O72-(aq) + 2OH-(aq) ⇌ 2CrO42-(aq) + H2O(l)
Keq = 4.14
The concentration of ions at equilibrium was measured at a specific temperature and found to be
[CrO42-] = 0.100 M and [Cr2O72-] = 0.20 M. What is the equilibrium [OH-]?
A.
0.012 M
B.
0.083 M
C.
0.13 M
D.
0.11 M
28.
Consider the following equilibrium:
CH4(g) + H2O(g) ⇌ CO2(g) + 3H2(g)
Keq = 5.67
An equilibrium mixture of this system was found to contain the following concentrations:
[CH4] = 0.59 M , [H2O] = 0.63 M, [CO2] = 0.25 M.
What was the equilibrium [H2]?
A.
0.26 M
B.
0.64 M
C.
2.0 M
D.
8.4 M
Equilibrium Quiz # 5 Calculations and Trial Keq
1.
Consider the following equilibrium: N2(g) + O2(g) ⇄ 2NO(g) Keq = 0.010
Initially, a 1.0 L container is filled with 0.40 mol of N 2, 0.10 mol of O2 and
0.080 mol of NO. As the system approaches equilibrium, the
A.
[NO], [N2] and [O2] remain unchanged
B.
[NO] increases and both [N2] and [O2] decrease
C.
[NO] decreases and both [N2] and [O2] increase
D.
[NO] decreases and both [N2] and [O2] remain unchanged
2.
Consider the following equilibrium: 2O2(g) + N2(g) ⇄
N2O4(g)
When 2.0 mol of O2 and 3.0 mol of N2 were placed in a 10.0 L container at 25oC, the value of Keq=0.90. If
the same number of moles of reactant were placed in a 5.0 L container at 25 oC, the equilibrium constant
would be
A.
0.011
B.
0.45
C.
0.90
D.
1.80
3.
Consider equilibrium system at 900oC:
H2O(g) + CO(g) ⇄ H2(g) + CO2(g)
Initially, 5.0 moles of H2O and 4.0 moles of CO were reacted. At equilibrium, it is found that 2.0 moles of
H2 are present. How many moles of H2O remain in the mixture?
A.
1.0 moles
B.
2.0 moles
C.
3.0 moles
D.
4.0 moles
4.
Consider the following equilibrium: PCl5(g) ⇄ PCl3(g) + Cl2(g)
Keq=33.3
Predict what will occur when 2.0 mol of PCl5, 3.0 mol of PCl3 and 4.0 mol of Cl2 are placed in a 1.0 L
container and allowed to establish equilibrium.
A.
[PCl5] will increase
B.
[PCl3] and [Cl2] will both increase
C.
[PCl5] and [Cl2] will both increase
D.
[PCl5] and [PCl3] will both decrease
5.
Consider the equilibrium system: CO(g) + 2H2(g) ⇄ CH3OH(g) ∆H= -18kJ
In order to increase the value of Keq for this reaction, you could
A.
Increase [CO]
B.
Increase the volume
C.
Decrease [CH3OH]
D.
Decrease the temperature
6.
Consider the following: SO2Cl2(g) ⇄ SO2(g) + Cl2(g)
A 1.0 L container is initially filled with 2.0 mol of SO 2Cl2. As the reaction proceeds towards equilibrium,
the rate of the forward reaction
A.
Increases and the [SO2] increases
B.
Increases and the [SO2] Decreases
C.
Decreases and the [SO2] increases
D.
Decreases and the [SO2] decreases
7.
Consider the following: 2NO2(g) ⇄
N2O2(g) Keq=1.20
A 1.0 L of flask is filled with 1.4 mol NO2 and 2.0 mol N2O4. To reach equilibrium, the reaction proceeds
to the
A.
Left as Trial Keq > Keq
B.
Left as Trial Keq < Keq
C.
Right as Trial Keq > Keq
D.
Right as Trial Keq < Keq
8.
Consider the following: 2C(s) + O2(g)
⇄
2CO(g)
A 1.0 L flask is initially filled with 2.00 mol C and 0.500 mol O 2. At equilibrium the [O2] is 0.250 mol/L.
The Keq value is
A.
0.444
B.
1.00
C.
2.00
D.
2.25
9.
Consider the following: 2H2O(g)
⇄
2H2(g) + O2(g)
When 0.1010 mol H2O is placed in a 1.000 L container, equilibrium is established. The equilibrium
concentration of O2 is 0.0010 mol/L. the equilibrium concentrations of H 2O and H2 are
[H2O]
0.0990
0.1000
0.1005
0.1010
A
B
C
D
10.
[H2]
0.0020
0.0010
0.0005
0.0020
Which of the following equilibrium systems most favors the products?
⇄
2Cl(g)
Keq=6.4 x 10-39
Cl2(g) + 2NO(g)
⇄ 2NOCl(g)
Keq=3.7 x 108
C.
Cl2(g) + 2NO2(g)
⇄
Keq=1.8
D.
2HCl(g) ⇄
A.
Cl2(g)
B.
2NO2Cl(g)
H2(g) + Cl2(g)
Keq=2.0 x 10-3
11.
Consider the equilibrium: H2O(g) + Cl2O(g) ⇄ 2HOCl(g) Keq= 9.0 x 10-2
A 1.0 L flask contains a mixture of 1.8 x 10 -1 mol H2O. 4.0 x 10-4 mol Cl2O, and
8.0 x 10-2 mol HOCl . To establish equilibrium, the system will proceed to the
A.
Left as Trial Keq > Keq
B.
Left as Trial Keq < Keq
C.
Right as Trial Keq > Keq
D.
Right as Trial Keq < Keq
12.
Consider the following equilibrium: 2O3(g) ⇄ 3O2(g)
Keq=55
If 0.060 mol of O3 and 0.70 mol of O2 are introduced into a 1.0 L vessel, the
A.
Ktrial > Keq and the [O2] increases
B.
Ktrial < Keq and the [O2] increases
C.
Ktrial > Keq and the [O2] decreases
D.
Ktrial < Keq and the [O2] decreases
13.
Consider the following equilibrium: CO(g) + Cl2(g) ⇄
COCl2(g)
At equilibrium, a 2.0 L sample was found to contain 1.00 mol CO, 0.500 mol Cl2 and 0.100 mol COCl2.
The Keq value for the above system is
A.
0.40
B.
0.20
C.
2.5
D.
5.0
14
Consider the following equilibrium: 2SO2(g) + O2(g)⇄
2SO3(g)
Keq=4.0
In an experiment, 0.40 mol SO2(g), 0.20 mol O2(g) and 0.40 mol SO3(g) are placed into a 1.0 liter container.
Which of the following statements relates the changes in [SO2] and [O2] as equilibrium becomes
established?
A.
The [SO2] and [O2] increase
B.
C.
D.
The [SO2] and [O2] decrease
The [SO2] and [O2] do not change
The [SO2] increases and the [O2] decreases
15.
Consider the following equilibrium system: H2(g) + S(s) ⇄
H2S(g)
In a 1.0 L container at equilibrium there are 0.050 mol H 2, 0.050 mol S and 1.0 mol H2S. The value of Keq
is
A.
2.5 x 10-3
B.
5.0 x 10-2
C.
2.0 x 101
D.
4.0 x 102
16.
Consider the following equilibrium and experimental data:
N2O4(g)
Trial 1
Trial 2
⇄
2NO2(g)
Initial
[N2O4]
[NO2]
Equilibrium
[N2O4]
[NO2]
0.0400 M
0.0200 M
0.0337 M
0.0429 M
0.0125 M
0.0141 M
0.0000 M
0.0600 M
Which of the following represents the Keq value?
A.
0.00464
B.
0.371
C.
0.742
D.
216
17.
Consider the following equilibrium:
Cl2(g) + 2NO(g) ⇌ 2NOCl(g)
At equilibrium, [Cl2] = 1.0 M and [NO] = 2.0 M.
What is the [NOCl] at equilibrium?
A.
0.80 M
B.
0.89 M
C.
4.5 M
D.
10 M
18.
Consider the following equilibrium:
Cl2(g) + 2NO(g) ⇌ 2NOCl(g)
If 12.0 moles of Cl2, 10.24 moles of NO, and 2.00 moles NOCl are placed in a 2.00 L container and the
system moves to the right to get to equilibrium, If there are 10.0 moles NOCl at equilibrium, calculate the
Keq.
A.
0.996
B.
5.58
C.
1.12
D.
4.98
19.
What will cause the value of Keq for an exothermic reaction to decrease?
A.
increasing the pressure
B.
increasing the temperature
C.
decreasing the temperature
D.
decreasing the surface area
20.
Consider the following: H2(g) + I2(g) ⇌ 2HI(g) Initially, some HI is placed into a 1.0 L container. At
equilibrium there are 0.010 mol H2, 0.010 mol I2 and 0.070 mol HI present. How many moles of HI were
initially added to the container?
A.
0.060 mol
Keq = 5.0
B.
C.
D.
0.070 mol
0.080 mol
0.090 mol
21.
Consider the following equilibrium: 3NO2(g) ⇌ N2O5(g) + NO(g).
Initially, some NO2, N2O5 and NO were placed in a container and allowed to reach equilibrium. When
equilibrium was established, it was found that the pressure had increased. Which of the following explains
what happened?
A.
Trial Keq > Keq so the system shifted left.
B.
Trial Keq < Keq so the system shifted left.
C.
Trial Keq > Keq so the system shifted right.
D.
Trial Keq < Keq so the system shifted right.
22.
Consider the following equilibrium: 3NO2(g) ⇌ N2O5(g) + NO(g).
Initially, 8.00 moles NO2 were placed in a 2.0 L container and allowed to reach equilibrium. The
equilibrium concentration of NO was 1.10 M. Calculate the Keq.
A.
1.7
B.
1.9
C.
3.5
D.
0.050
23.
Consider the following equilibrium: 3NO2(g) ⇌ N2O5(g) + NO(g).
At a different temperature, 4.00 M NO2 were placed in a 2.0 L container and allowed to reach equilibrium.
The equilibrium concentration of NO2 was 1.00 M. Calculate the Keq.
A.
0.11
B.
1.0
C.
3.0
D.
10.
24.
Consider the reaction: 2HBr(g) ⇌ H2(g) + Br2(g) Keq = 49.0
If 4.0 M HBr is initially placed into a container, what will be the equilibrium [HBr]?
A.
2.0 M
B.
3.7 M
C.
5.3 M
D.
8.8 M
25.
Consider the reaction: 2HBr(g) ⇌ H2(g) + Br2(g) Keq = 49.0
If 0.120 M H2, 0.120 M Br2 and 0.01714 M HBr are placed into a container at
440 C, which of the following is true as equilibrium is approached?
A.
[Br2] decreases significantly.
B.
[HBr] decreases significantly.
C.
[H2] decreases significantly.
D.
[H2] remains the same.
26.
Consider the reaction: 2HBr(g) ⇌ H2(g) + Br2(g) Keq = 49.0
If 1.20 M H2, 1.20 M Br2 and 1.00 M HBr are placed into a container at
440 C, which of the following is true as equilibrium is approached?
A.
[Br2] decreases significantly.
B.
[HBr] decreases significantly.
C.
[H2] decreases significantly.
D.
[H2] remains the same.
27.
Which Keq is most likely to favour the formation of reactants?
A.
Keq = 1.65 x 104
B.
C.
D.
28.
Keq = 5.69 x 10-11
Keq = 3.95 x 10-11
Keq = 7.67 x 104
Which Keq is most likely to favour the formation of products?
A.
B.
C.
D.
Keq
Keq
Keq
Keq
=
=
=
=
1.65
5.69
3.95
7.67
x
x
x
x
10-4
10-11
10-11
10-4
29.
Consider the following equilibrium system: 2NO(g) + Cl2(g) ⇌ 2NOCl(g) + 25 kJ
In which direction will the equilibrium shift and what happens to the value of Keq when the temperature of
the system is increased?
Shift
Keq
A.
right
increases
B.
right
decreases
C.
left
increases
D.
left
decreases
30.
Consider the following equilibrium system: 2NO(g) + Cl2(g) ⇌ 2NOCl(g) + 25 kJ
In which direction will the equilibrium shift and what happens to the value of Keq when NO is added?
Shift
Keq
A.
right
increases
B.
right
constant
C.
left
increases
D.
left
constant
31.
Consider the following equilibrium: 2COF2(g) ⇌ CO2(g) + CF4(g)
Initially, 0.32 M CO2 and 0.40 M CF4 are placed in a container. At equilibrium, it is found that the [COF2]
is 0.16 M. What is the value of Keq?
A.
0.026
B.
1.5
C.
9.3
D.
3.0
32.
Consider the following equilibrium:
CCl4(g) ⇌ C(s) + Cl2(g)
Initially, 0.62 mol CCl4 was placed in a 2.0L container.
At equilibrium, [Cl2] = 0.060 M. Which of the following is the value of Keq?
A.
0.00039
B.
0.24
C.
0.014
D.
0.78
33.
Consider the following equilibrium: 2COF2(g) ⇌ CO2(g) + CF4(g) Initially, 0.16 M
CF4 are placed in a container. At equilibrium, it is found that the [COF2] is 0.080 M.
What is the value of Keq?
A.
0.12
B.
1.5
C.
8.0
D.
3.0
CO2 and 0.20 M
Equilibrium
1.
2.
Quiz #6 Enthalpy and Entropy
In which of the following reactions does the tendency towards minimum enthalpy and maximum entropy
oppose each other?
⇄ 2O2(g)
ΔH = +285 KJ
A.
3O3(g)
B.
1/2O2(g) + O2(g) ⇄ NO2(g)
ΔH = +34 KJ
C.
2H2O(g) ⇄ 2H2(g) + O2(g)
ΔH = +484 KJ
D.
P4(s) + 6H2(g) ⇄ 4PH3(g)
ΔH = +37 KJ
In which of the following systems will the factors of entropy and enthalpy both favour the reactants.
A.
3C(s) + 3H2(g) + heat
B.
PCl5(g)
+
heat ⇄
C.
NH4Cl(s)
+ heat
D.
Cl2(g) + 2HI(g)
⇄
⇄
⇄ C3H6(g)
PCl3(g)
+
NH4+(aq)
Cl2(g)
+
Cl-(aq)
I2(g) + 2HI(g) + heat
3.
For an exothermic reaction at equilibrium, an increase in temperature will cause the equilibrium to shift
A.
left and the Keq increases
B.
left and the Keq decreases
C.
right and the Keq increases
D.
right and the Keq decreases
4.
Consider the equilibrium: COCl2(g) ⇄ CO(g) + Cl2(g)
For the above system,
A.
[COCl2] < [CO][Cl2]
B.
[COCl2] = [CO][Cl2]
C.
[COCl2] > [CO][Cl2]
D.
[COCl2] = 1/[CO][Cl2]
5.
The value of the equilibrium constant will change when
A.
a catalyst is used
B.
temperature changes
C.
product concentrations change
D.
the volume of a gaseous system changes
6.
In an exothermic equilibrium reaction involving only gases, the value of the Keq can be decreased by
A.
adding some reactant gas
B.
removing some reactant gas
C.
increasing the temperature
D.
decreasing the temperature
7.
Consider the equilibrium: H2(g) + CO2(g) ⇄ CO(g) + H2O(g) ΔH = +41KJ
The temperature of the above equilibrium system is increased while kept at a constant volume. A new state
of equilibrium is established in which there is
A.
an increase in [CO] and a decrease in Keq
B.
an increase in [CO] and a increase in Keq
C.
an increase in [CO2] and a decrease in Keq
D.
an increase in [CO2] and a increase in Keq
Keq = 8.1 x 10-4
8.
Consider the following equilibrium: 2NO2(g) ⇄ N2O4(g) + 59KJ
For the above reaction,
A.
both minimum enthalpy and maximum entropy favour the products.
B.
both minimum enthalpy and maximum entropy favour the reactants.
C.
minimum enthalpy favours reactants and maximum entropy favours products.
D.
minimum enthalpy favours products and maximum entropy favours reactants.
9.
In which of the following does entropy decrease?
A.
NaCl(s) → Na+(aq) + Cl-(aq)
B.
4NO(g) + 6H2O(g) → 4NH3(g) + 5O2(g)
C.
2NaCHCO3(s) → Na2CO3(s) + CO2(g) + H2O(g)
D.
CaCO3(s) + HCl(aq) → CaCl2(aq) + CO2(g) + H2O(l)
10.
Consider the following possible reaction: N2O(g) + NO2(g) → 3NO(g) + heat
Which of the following statements is correct?
A.
Minimum enthalpy and maximum entropy both favour the products.
B.
Minimum enthalpy and maximum entropy both favour the reactants.
C.
Minimum enthalpy favours the reactants and maximum entropy favours the products.
D.
Minimum enthalpy favours the products and maximum entropy favours the reactants.
11.
Consider the following equilibrium: COCl2(g) ⇄ CO(g) + Cl2(g)
At equilibrium in a 1.0L container, there are 3.0 mol COCl 2, 0.49 mol CO, and 0.49 mol Cl 2. At constant
temperature the volume of the above system is decreased to 0.50L. When equilibrium is reestablished the
A.
concentrations of all three gases have increased
B.
concentrations of all three gases have decreased
C.
[COCl2] has increased and [CO] and [Cl2] have decreased
D.
[COCl2] has decreased and [CO] and [Cl2] have increased
12.
Chemical systems move toward positions of
A.
minimum enthalpy and maximum entropy
B.
maximum enthalpy and minimum entropy
C.
constant enthalpy and constant entropy
D.
maximum enthalpy and maximum entropy
13.
Hydrogen gas dissociates into atomic hydrogen as follows:
H2(g) ⇄ 2H(g) Keq = 1.2 x 10-71
The value of the equilibrium constant for the above system indicates that
A.
the reaction rate is very slow
B.
the equilibrium is exothermic
C.
reactants are favoured in this equilibrium
D.
a catalyst is necessary to establish equilibrium
14.
Consider the following reaction:
Na2CO3(s) + HCl(aq) ⇄ 2NaCl(aq) + CO2(g) + H2O(l) ΔH = -27.7 KJ
In this reaction,
A.
Minimum enthalpy and maximum entropy both favour the products.
B.
Minimum enthalpy and maximum entropy both favour the reactants.
C.
Minimum enthalpy favours the products and maximum entropy favours the reactants.
D.
Minimum enthalpy favours the reactants and maximum entropy favours the products.
15.
In an endothermic equilibrium system, the
A.
Minimum enthalpy and maximum entropy both favour the products.
B.
Minimum enthalpy and maximum entropy both favour the reactants.
C.
Minimum enthalpy favours the products and maximum entropy favours the reactants.
D.
Minimum enthalpy favours the reactants and maximum entropy favours the products.
16.
Which of the following describes how a Keq value is related to the relative concentrations of reactants and
products?
Keq value
Relative Concentration
I.
large
[products] > [reactants]
II.
large
[reactants] > [products]
III.
small
[products] > [reactants]
IV.
small
[reactants] > [products]
A.
I only
B.
IV only
C.
I and IV only
D.
II and III only
17.
Consider the following equilibrium: N2(g) + O2(g) ⇌ 2NO(g) + 25.6 kJ
Under certain conditions, Keq = 0.00056. When conditions are changed, Keq becomes 0.0256. Which of
the following could account for this?
A.
[N2] was changed.
B.
A catalyst was added.
C.
Temperature was decreased.
D.
Temperature was increased.
18.
Consider the following equilibrium: N2O(g) + NO2(g) ⇌ 3NO(g) + 120 KJ
Under certain conditions, Keq = 2.5. When conditions are changed, Keq becomes 0.15. Which of the
following could account for this?
A.
[N2O] was added.
B.
A catalyst was added.
C.
Temperature was decreased.
D.
Temperature was increased.
19.
Reacting systems tend toward which of the following?
Entropy
Enthalpy
A.
minimum
maximum
B.
minimum
minimum
C.
maximum
minimum
D.
maximum
maximum
20.
Consider the following equation: NH4NO3(g) ⇌N2O(g) + 2H2O(g) + 37 kJ
Which of the following is true?
Enthalpy Favours Entropy Favours Outcome
A.
reactants
reactants
does not occur
B.
products
products
completion
C.
reactants
products
equilibrium
D.
products
reactants
equilibrium
21.
Consider:
energy + N2O4(g) ⇄
2NO2(g)
The system above reaches equilibrium. Considering enthalpy and entropy factors, which of the following
is true with respect to the forward reaction?
A.
The entropy is increasing and the reaction is exothermic.
B.
The entropy is decreasing and the reaction is exothermic.
C.
The entropy is increasing and the reaction is endothermic.
D.
The entropy is decreasing and the reaction is endothermic.
22.
Which of the following forward reaction changes would result in the most products?
Entropy
Enthalpy
A.
decreasing
decreasing
B.
increasing
decreasing
C.
decreasing
increasing
D.
increasing
increasing
23.
Which of the following forward reaction changes would result in the most reactants?
Entropy
Enthalpy
A.
decreasing
decreasing
B.
increasing
decreasing
C.
decreasing
increasing
D.
increasing
increasing
24.
Which of the following forward reaction changes would result equilibrium?
Entropy
Enthalpy
A.
decreasing
decreasing
B.
increasing
decreasing
C.
decreasing
increasing
D.
constant
constant
25.
When the temperature of an endothermic equilibrium is increased, which of the following will happen?
A.
Equilibrium will shift left and [products] will increase.
B.
Equilibrium will shift left and [products] will decrease.
C.
Equilibrium will shift right and [reactants] will increase.
D.
Equilibrium will shift right and [reactants] will decrease.
26.
When the temperature of an exothermic equilibrium is decreased, which of the following will happen?
A.
Equilibrium will shift left and [products] will increase.
B.
Equilibrium will shift left and [products] will decrease.
C.
Equilibrium will shift right and [reactants] will increase.
D.
Equilibrium will shift right and [reactants] will decrease.
27.
When the temperature of an endothermic equilibrium is increased, which of the following will happen?
A.
Equilibrium will shift left and the Keq will increase.
B.
Equilibrium will shift right and the Keq will increase.
C.
Equilibrium will shift left and the Keq will stay constant.
D.
Equilibrium will shift right and the Keq will stay constant.
28.
Consider: 2Li(s) + H2O(l)  2LiOH(aq) + H2(g) ΔH = -256 kJ?
What will entropy and enthalpy factors favour?
Entropy
Enthalpy
A.
products
reactants
B.
products
products
C.
reactants
reactants
D.
reactants
products
29.
Consider: 3C(s) + 3H2(g) + heat ⇄ C3H6(g)
What will entropy and enthalpy factors favour?
Entropy
Enthalpy
A.
products
reactants
B.
products
products
C.
reactants
reactants
D.
reactants
products
30.
In order for a chemical reaction to go to completion, how must the entropy and enthalpy change?
A.
B.
C.
D.
enthalpy
increases
increases
decreases
decreases
entropy
increases
decreases
increases
decreases
Web Review
1.
Describe the changes in reactant and product concentration as equilibrium is approached.
2.
Describe the changes in the forward and the reverse rates as equilibrium is approached.
3.
State three conditions that are necessary to achieve equilibrium.
4.
Assuming all three conditions are present, describe what would happen if only reactants
are placed in a container.
5.
Assuming all three conditions are present, describe what would happen if only
products are placed in a container.
6.
Describe the relationship between the size of the equilibrium constant, large, small, or
about 1, and the relative amounts of reactants or products.
7.
Describe each of the following:
Dynamic equilibrium,
LeChatelier's principle,
Ktrial,
Enthalpy,
Entropy
Macroscopic property.
8.
Describe the effect of temperature on the equilibrium constant for an exothermic and
endothermic reaction.
9.
Describe the effect of changing the temperature, pressure , volume, concentration or
adding a catalyst on the value of the equilibrium constant.
10.
What is the only variable that will change the value of the equilibrium constant.
11.
What are the phases of the compounds that are not included in the equilibrium
expression.
12.
Write the equilibrium expression for: 4A(g) + 3B(aq) ⇄ 2C(l) + 3D(s)
13.
Pick the best Keq for each of the reactions.
Keq = 100
Keq = 0.01
Keq = 1.0
14.
15.
a)
Zn(s) + 2HCl(aq) → ZnCl2(aq) + H2(g) + 152kJ
b)
3C(s) + 3H2(g) ⇄ C3H6(g)
c)
2Pb(NO3)2(s) + 597 kJ ⇄ 2PbO(s) +4NO2(g) + O2(aq)
ΔH = +20.4 kJ
For each reaction in equilibrium describe the shift for the following changes: increasing
temperature, increasing pressure, decreasing volume, adding a gaseous product and
removing an aqueous reactant.
a)
Zn(s) + 2HCl(aq) ⇄ ZnCl2(aq) + H2(g) + 152kJ
b)
A(aq) + 6B(g) ⇄ 2C(g) + 4D(g) ΔH= +56kJ
Zn(s) + 2HCl(aq) ⇄ ZnCl2(aq) + H2(g) + 152kJ
Give three ways to increase the yield of the reaction.
Give five ways to increase the rate of the reaction.
16.
A(aq) + 6B(g) ⇄ 2C(g) + 2D(g) ΔH= +56kJ
Give three ways to increase the yield of the reaction.
Give five ways to increase the rate of the reaction.
17.
What is equal at equilibrium?
18.
What is constant at equilibrium?
19.
Which reaction has the greatest yield? Why?
a) Keq = 8.0 x 10-12
20.
Which reaction has the smallest yield?
a) Keq = 1.0 x 10-15
21.
b) Keq = 7.0 x 10-11
b) Keq = 9.0 x 10-15
Which has the greater entropy?
a) H2O(s)
b) H2O(l)
c) H2O(g)
22.
Which has the greater enthalpy?
a) H2O(s)
b) H2O(l)
c) H2O(g)
Hint: Consider H2O(s) → H2O(l) Draw a potential energy diagram. Which side is higher?
23.
Review your kinetics test. There will be 5 questions on this test from kinetics.
24.
Consider the following equilibrium system: SO3(g) + NO(g)⇄NO2(g) + SO2(g)
a)
Describe what happens to the forward and reverse reaction rate immediately after
adding SO3(g)
b)
Describe what happens to the forward and reverse reaction rate immediately after
removing NO2(g)
c)
Describe what happens to the forward and reverse reaction rate immediately after
adding a catalyst .
d)
Describe what happens to the forward and reverse reaction rate after a new
equilibrium has formed compared to the original equilibrium after removing
NO2(g)
e)
Describe what happens to the forward and reverse reaction rate after a new
equilibrium has formed compared to the original equilibrium after adding SO3(g)
f)
Describe what happens to the forward and reverse reaction rate after a new
equilibrium has formed compared to the original equilibrium after adding a
catalyst .
g)
Describe what happens to the forward and reverse reaction rate after a new
equilibrium has formed compared to the original equilibrium after decreasing the
volume of the container.
h)
Describe what happens to the reactant and product concentrations after a new
equilibrium has formed compared to the original equilibrium after decreasing the
volume of the container.
Part 2
Calculations
1.
SO3(g) + NO(g) ⇄ NO2(g) + SO2(g)
[SO3] = 0.400M [NO] = 0.480M
[NO2] = 0.600M [SO2] = 0.450M Keq = 0.800 at 100ºC
a) Show by calculation that this reaction mixture is not at equilibrium at 100ºC.
b) What will happen to [SO3] and [SO2] as the system moves to equilibrium?
2.
Consider the equilibrium below:
Co(H2O)6+2(aq) + 2Cl-1(aq) ⇄ Co(H2O)6Cl2(aq) + 2H2O(l)
pink
blue
If the colour of the equilibrium mixture is pink at 5ºC and blue at 60ºC, is the reaction
endothermic or exothermic?
3.
SO3(g) + H2O(g) ⇄ H2SO4(l)
If The equilibrium concentrations are :[SO3] = 0.400M [H2O] = 0.480M
[H2SO4] = 0.600M. Calculate the value of the equilibrium constant.
4.
2SO2(g) + O2(g) ⇄ 2SO3(g)
4.00 moles of SO2 and 5.00 moles O2 are placed in a 2.00 L container at 200ºC and
allowed to reach equilibrium. If the equilibrium concentration of O2 is 2.00M, calculate
the Keq.
5.
2SO2(g) + O2(g) ⇄ 2SO3(g)
If at equilibrium [O2] = 0.500M and [SO3] = 0.400M and the equilibrium constant is the
same as question 4 at 200ºC, calculate the [SO2].
6.
Consider the following equilibrium:
2NO2(g) ⇄ N2O4(g)
2.00 moles of NO2 are placed in a 1.00 L flask and allowed to react. At equilibrium
1.80M NO2 are present. Calculate the Keq.
7.
SO3(g) + NO(g) ⇄ NO2(g) + SO2(g) Keq = 0.800 at 100ºC
If 4.00 moles of each reactant is placed in a 2.00L container, calculate all equilibrium
concentrations at 100ºC.
8.
Keq = 0.0183 at 150ºC for: 2HI(g) ⇄ H2(g) + I2(g)
If 3.00 moles of HI is placed in a 5.00 L container and allowed to establish equilibrium,
what are all equilibrium concentrations?
9.
Consider the following equilibrium in a 5.00 L container:
CO (g) + H2O (g) ⇄ CO2(g) + H2 (g)
At equilibrium, there is 1.0 mole of CO, 3.0 moles of H2O, 3.0 moles CO2, and 3.0 moles
of H2. If 2.0 moles of CO are now added, find the equilibrium [CO2].
Hint: first calculate the Keq, then do an ICE chart with the initial concentrations after CO
is added.
Equilibrium Practice Test # 1
1.
Consider the following reaction mechanism:
Step1: NO(g) + O3(g) → NO2(g)
+ O2(g)
Step2: O(g)
+ NO2(g)
→ NO(g)
+ O2(g)
The catalyst is:
A.
O2
B.
O3
C.
NO
D.
NO2
2.
Consider the following reaction: 2NH3(g) ⇄ N2(g) + 3H2(g)
A flask is initially filled with NH3. As the system approaches equilibrium, the rate of the forward reaction
A.
increases as the rate of the reverse reaction decreases
B.
decreases as the rate of the reverse reaction increases
C.
increases as the rate of the reverse reaction increases
D.
decreases as the rate of the reverse reaction decreases
3.
Consider the following reaction:
Na2CO3(s) + 2HCl(aq) → 2NaCl(aq) + CO2(g) + H2O(l)
ΔH = -153 KJ
In this reaction
A.
minimum enthalpy and maximum entropy both favour the products
B.
minimum enthalpy and maximum entropy both favour the reactants
C.
minimum enthalpy favours products and maximum entropy reactants
D.
minimum enthalpy favours reactants and maximum entropy products
4.
In all systems at equilibrium, the
A.
concentration of reactants is less than the concentration of the products
B.
concentration of reactants and the concentration of the products are equal
C.
concentration of reactants is greater than the concentration of the products
D.
concentration of reactants and the products are constant
5.
Consider the following mechanism: Step 1:
N2O(g)
→ N2(g) + O(g)
Step 2: N2O(g) + O(g) → N2(g) + O2(g)
A reactant in the overall equation is
A.
B.
C.
D.
O
O2
N2
N2O
6.
Chemical systems tend to move toward positions of
A.
minimum enthalpy and maximum entropy.
B.
maximum enthalpy and minimum entropy.
C.
minimum enthalpy and minimum entropy.
D.
maximum enthalpy and maximum entropy.
7.
An equilibrium system shifts left when the
A.
rate of the forward reaction is equal to the rate of the reverse reaction.
B.
rate of the forward reaction is less than the rate of the reverse reaction.
C.
rate of the forward reaction is greater than the rate of the reverse reaction.
D.
rate of the forward reaction and the reverse reaction are constant.
8.
A 1.00 L flask contains a gaseous equilibrium system. The addition of reactants to this flask results in a
A.
shift left and a decrease in the concentration of the products.
B.
shift left and a increase in the concentration of the products.
C.
shift right and a decrease in the concentration of the products.
D.
shift right and a increase in the concentration of the products.
9.
Consider the following equilibrium: CH4(g) + H2O(g) + heat ⇄ CO(g) + 3H2(g)
In which of the following will both stresses shift the equilibrium to the right?
A.
a decrease in temperature and a decrease in volume
B.
a increase in temperature and a decrease in volume
C.
a decrease in temperature and a increase in volume
D.
a increase in temperature and a increase in volume
10.
Consider the following equilibrium: 2SO2(g) + O2(g) ⇄ 2SO3(g) ∆H = -198 kJ
There will be no shift in this equilibrium when
A.
more O2 is added.
B.
a catalyst is added.
C.
the volume is increased.
D.
the temperature is increased.
11.
Consider the following equilibrium: 2Fe(s) + 3H2O(g) ⇄ Fe2O3(s) + 3H2(g)
The equilibrium expression is
12.
A.
Keq = [Fe2O3][H2]3
[Fe]2[H2O]3
C.
Keq =
[H2]3
[H2O]3
B.
D.
Keq = [ H2]3
Consider the following equilibrium: N2O4(g) ⇄ 2NO2(g)
At equilibrium, the [N2O4] is equal to
A.
0.133
[NO2]
Keq = [Fe2O3][3H2]
[2Fe][3H2O]
B.
Keq = 0.133
[NO2]
0.133
C.
13.
14.
0.133
[NO2]2
D.
[NO2]2
0.133
Which of the following equilibrium systems most favours the products?
A.
Cl2(g) ⇄ 2Cl(g)
B.
Cl2(g) + 2NO(g) ⇄ 2NOCl(g)
C.
Cl2(g) + 2NO2(g) ⇄ 2NO2Cl(g)
Keq = 1.8
D.
2HCl(g) ⇄ H2(g) + Cl2(g)
Keq = 2.0 x 10-7
Keq = 6.4 x 10-39
Keq = 3.7 x 108
Consider the following equilibrium: 4KO2(s) + 2H2O(g) ⇄ 4KOH(s) + 3O2(g)
The equilibrium expression is
A.
Keq = [KOH]4[O2]3
[KO2]2[H2O]2
B.
Keq = [O2]3
[ H2O]2
C.
Keq = [KO2]4[H2O]2
[KOH]4[O2]3
D.
Keq = [ H2O]2
[O2]3
15.
Consider the following equilibrium: N2(g) + O2(g) ⇄ 2NO(g)
When the temperature is decreased, the equilibrium:
A.
shifts left and the Keq value increases
B.
shifts left and the Keq value decreases
C.
shifts right and the Keq value increases
D.
shifts right and the Keq value decreases
16.
Consider the following equilibrium: CaCO3(s) + 556 kJ ⇄ CaO + CO2(g)
The value of the equilibrium constant will increase when
A.
CO2 is added.
B.
CO2 is removed.
C.
the temperature is increased.
D.
the temperature is decreased.
17.
Consider the following equilibrium: C(s) + H2O(g) ⇄ CO(g) + H2(g)
The contents of a 1.00 L container at equilibrium were analyzed and found to contain 0.20 mole C, 0.20
mole H2O, 0.60 mole CO, and 0.60 mole H2, The equilibrium constant is
A.
0.11
B.
0.56
C.
1.8
D.
0.0
18.
Consider the following equilibrium: N2O4(g) ⇄ 2NO2(g)
Keq = 4.61 x 10-3
A 1.00 L container at equilibrium was analyzed and found to contain
0.0200 mole NO2. At equilibrium, the concentration of N2O4 is
A.
0.0868 M
B.
0.230 M
C.
4.34 M
D.
11.5 M
19.
PE
(kJ)
Consider the following potential energy diagram:
225kJ
Progress of Reaction
50kJ
∆H = +181 kJ
The forward reaction is
A.
B.
C.
D.
exothermic and the
endothermic and the
exothermic and the
endothermic and the
∆H
∆H
∆H
∆H
=
=
=
=
-50 kJ
+50 kJ
-225 kJ
+225 kJ
20.
Consider the following equilibrium: H2O(g) + CO(g) ⇄ H2(g) + CO2(g)
A closed container is initially filled with H2O and CO. As the reaction proceeds to equilibrium the
A.
[CO] and [CO2] both increase
B.
[CO] and [CO2] both decrease
C.
[CO] increases and [CO2] decreases
D.
[CO] decreases and [CO2] increases
21.
Consider the equilibrium: H2(g) + I2(g) ⇄ 2HI(g) The pressure of the system is increased by reducing the
volume. When comparing the new equilibrium with the original equilibrium,
A.
all concentrations remain constant
B.
the concentrations of all species have increased
C.
reactant concentrations have increased while products decreased
D.
reactant concentrations have decreased while products increased
22.
Consider the following equilibrium: N2O4(g) ⇄ 2NO2(g) A 1.00 L container is initially filled with 0.200
moles of N2O4. At equilibrium, 0.160 moles NO2 are present. What is the equilibrium concentration of
N2O4?
A.
0.040 M
B.
0.080 M
C.
0.120 M
D.
0.160 M
23.
Equilibrium is dynamic process because the
A.
macroscopic properties are not changing
B.
mass of the reactants equals the mass of the products
C.
forward and reverse reactions continue to occur
D.
concentrations of reactants and products are constant
24.
Consider the following equilibrium: C(s) + 2H2(g) ⇄ CH4(g) The addition of H2 will cause the equilibrium
to shift to the
A.
left and [CH4] will increase
B.
left and [CH4] will decrease
C.
right and [CH4] will increase
D.
right and [CH4] will decrease
25.
Given the following system: 2CrO42-(aq) + 2H+(aq) ⇄ Cr2O72-(aq) + H2O(l) Which of the following
chemicals, when added to the above equilibrium, would result in a decrease in [CrO 42-]?
A.
NaOH
B.
HNO3
C.
Na2CrO4
D.
Na2Cr2O7
26.
Addition of a catalyst to an equilibrium system
A.
increases the value of the Keq.
B.
increases the yield of the products.
C.
has no effect on the rates of the reaction.
D.
increases the rate of formation of both reactants and products.
27.
Consider the following reaction: 2B(s) + 3F2(g) ⇄ 2BF3(g) The equilibrium expression is
A.
B.
C.
D.
Keq = [2BF3]
[3F2]
Keq = [F2]3
[BF3]
Keq = [BF3]2
[F2]3
Keq = [BF3]2
[B][F2]3
28.
Consider the following equilibrium: 2NO(g) ⇄ N2(g) + O2(g) Keq = 2.01 x 1030
The value of the equilibrium constant indicates that the
A.
[NO]2 < [N2][ O2]
B.
[NO]2 > [N2][ O2]
C.
[NO] = [N2][ O2]
D.
[NO] > [N2][ O2]
29.
Consider the equilibrium: H2(g) + I2(g) ⇄ 2HI(g)
At equilibrium the [H2} = 0.020 M, [I2] = 0.020 M, and [HI] = 0.160 M. The value of the equilibrium
constant is:
A.
2.5 x 10-3
B.
1.6 x 10-2
C.
6.4 x 101
D.
4.0 x 102
30.
Consider the equilibrium: H2O(g) + Cl2O(g) ⇄ 2HOCl(g) Keq = 9.0 x 10-2
A 1.0 L flask contains a mixture of 1.8 x 10 -1 mole H2O, 4.0 x 10-4 mole Cl2O, and 8.0 x 10-2 mole
HOCl. To establish equilibrium, the system will proceed to the
A.
left because the trial Keq > Keq
B.
left because the trial Keq < Keq
C.
right because the trial Keq > Keq
D.
right because the trial Keq < Keq
31.
Consider the following equilibrium: SO2(g) + NO2(g) ⇄ SO3(g) + NO(g) + energy
The equilibrium does not shift with a change in
A.
volume
B.
temperature
C.
concentration of products
D.
concentration of reactions
32.
Consider the following equilibrium : SO2Cl2(g) + energy ⇄ SO2(g) + Cl2(g)
When the temperature is decreased, the equilibrium shifts
A.
left and the [SO2Cl2] increases
B.
left and the [SO2Cl2] decreases
C.
right and the [SO2Cl2] increases
D.
right and the [SO2Cl2] decreases
33.
Consider the following equilibrium: NH3(g) + HCl(g) ⇄ NH4Cl(s) + energy
Which of the following will result in a decrease in the mass of NH 4Cl?
A.
B.
C.
D.
34.
adding NH3
removing HCl
decreasing the volume
decreasing the temperature
Consider the following equilibrium: PCl3(g) + Cl2(g) ⇄ PCl5(g)
When 0.40 moles of PCl3 and 0.40 moles of Cl2 are placed in a 1.00 L container and allowed to reach
equilibrium, 0.244 mole of PCl5 are present. From this information, the value of the Keq is
A.
0.10
B.
0.30
C.
3.3
D.
10
Subjective
1.
Concentrations of H2, I2, and HI in a mixture at equilibrium at 425 oC were found to be 1.52 x 10-2 M, 3.55
x 10-2 M, and 2.57 x 10-1 M respectively. Calculate the equilibrium constant.
H2(g)
2.
+
⇄
I2(g)
2HI(g)
4.00 moles of PCl5 are placed in a 2.00 L container and goes to equilibrium at
200 oC. If 0.60 moles of PCl5 are present at equilibrium, calculate the equilibrium constant.
PCl5(g)
⇄
PCl3(g)
+
Cl2(g)
3.
An equilibrium system has a Keq = 50 at 0 oC and a Keq = 80 at 20 oC.
a)
As the temperature was increased, which direction did the reaction shift?
b)
Is the reaction endothermic or exothermic?
4.
If the initial [H2] = 0.200 M and [I2] = 0.200 M and the Keq = 55.6 at 20 oC, calculate the equilibrium
concentration of all molecules.
H2(g)
5.
I2(g) ⇄
+
2HI(g)
Consider the following data obtained for the following equilibrium:
Fe3+(aq) +
SCN-(aq)
Experiment 1
⇄
FeSCN2+(aq)
[Fe3+]
[SCN-]
3.91 x 10-2 M
8.02 x 10-5 M
[FeSCN2+]
9.22 x 10-4 M
Experiment 2
6.27 x 10-3 M
3.65 x 10-4 M
Calculate [FeSCN2+] in experiment 2.
6.
1.60 moles CO, 1.60 moles H2O, 6.00 moles CO2, and 6.00 moles H2 are put in a
2.00 L container at 600 oC.
CO(g) + H2O(g) ⇄ CO2(g) + H2(g)
Keq = 10.0
a)
Show by calculation the reaction is not at equilibrium.
b)
Which way will the reaction shift in order to achieve equilibrium?
c)
Calculate the equilibrium concentration of CO2.
?
Equilibrium Practice Test # 2
1.
The slowest of the following reactions is:
A.
Ag+(aq) + Cl-(aq) → AgCl(s)
B.
H+(aq) + OH-(aq) → 2H2O(l)
C.
3Ba2+(aq) + 2PO43-(aq) → Ba3(PO4)2(aq)
D.
Cu(s) + 2Ag+(aq) → Cu2+(aq) + 2Ag(s)
2.
The rate of a chemical reaction is equal to the slope of the line with axes labelled
x-axis
y-axis
A.
B.
C.
D.
3.
time
mass
volume of gas
time
rate
time
time
concentration
Consider the following reaction: CH4(g) + 2O2(g) → CO2(g) + 2H2O(g) + heat
The diagram that represents the relationship between rate and temperature is:
B.
A.
Rate
Rate
C.
Temperature
D.
Temperature
Rate
Rate
Temperature
Temperature
4.
Which of the following describes the energy of colliding particles as reacting molecules approach each
other?
KE
PE
A.
decreases
increases
B.
increases
decreases
C.
decreases
remains constant
D.
remains constant increases
5.
The average kinetic energy per molecule can be increased by
A.
adding a catalyst
B.
increasing pressure
C.
increasing temperature
D.
increasing reactant concentration
6.
Consider the following reaction: C(s) + 2H2(g) ⇄ CH4(g)
ΔH = -74.8 kJ
Which of the following will cause an increase in the value of the Keq?
A.
increasing [H2]
B.
decreasing the volume
C.
finely powdering the C(s)
D.
decreasing the temperature
7.
Consider the following equilibrium: H2(g) + I2(g) ⇄ 2HI(g)
At equilibrium [H2] = 0.00220 M, [I2] = 0.00220 M, and [HI] = 0.0156 M
The value of the Keq is
A.
3.10 x 10-4
B.
1.99 x 10-2
C.
5.03 x 101
D.
3.22 x 103
8.
Consider the rate diagram for the following reaction: 2HI (g) ⇄ H2(g) + I2(g)
forward
Rate
reverse
Which of the following occurs at t1?
A.
addition of H2
B.
addition of HI
C.
addition of a catalyst
D.
a decrease in volume
Time
9.
Chemical equilibrium is said to be dynamic because
A.
the reaction proceeds quickly
B.
the mass of the reactants is decreasing
C.
the macroscopic properties are constant
D.
both forward and reverse rates are occurring
10.
Which equation has the largest value of Keq
11.
t1
A.
N2(g) + O2(g) ⇄ 2NO(g)
ΔH = 21 kJ
B.
C2H6(g) ⇄ 2C(s) + 3H2(g)
ΔH + 83 kJ
C.
H2(g) + 1/2O2(g) ⇄ H2O(g)
D.
Ca(s) + 3H2O(l) ⇄ Ca(OH)2(aq) + H2(g)
The value of the Keq can be changed by
A.
adding a catalyst
B.
changing the temperature
C.
changing the reactant concentration
D.
changing the volume of the container
ΔH = -240 kJ
ΔH = -240 kJ
12.
Consider the following equilibrium: PCl3(g) + Cl2(g) ⇄ PCl5(g)
When 0.40 mole of PCl3 and 0.40 mole of Cl2 are placed in a 1.00 L container and allowed to reach
equilibrium, 0.244 mole of PCl5 are present. From this information, the value of the Keq is
A,
0.10
B.
0.30
C.
3.3
D.
10
13.
Consider the following equilibrium: PCl3(g) + Cl2(g) ⇄ PCl5(g)
Keq = 2.30
A 1.0 L container is filled with 0.05 mole PCl5, 1.0 mole PCl3, and 1.0 mole Cl2. The system proceeds to
the
A.
left because the Trial Keq > Keq
B.
left because the Trial Keq < Keq
C.
right because the Trial Keq > Keq
D.
right because the Trial Keq < Keq
14.
Given the following system: 2CrO42-(aq) + 2H+(aq) ⇄ Cr2O72-(aq) + H2O(l)
Which of the following chemicals, when added to the above system at equilibrium, would result in a
decrease in [Cr2O72-]?
A.
NaOH
B.
HNO3
C.
Na2CrO4
D.
Na2Cr2O7
15.
What is the Keq expression for the following equilibrium?
A.
B.
C.
D.
3Fe(s) + 4H2O(g) ⇄ Fe3O4(s) + 4H2(g)
Keq = [H2]4
Keq = [H2]
[H2O]
Keq = [H2]4
[H2O]4
Keq = [Fe2O3][H2]4
[Fe][H2O]4
16.
Consider the following equilibrium: 2O3(g) ⇄ 3O2(g) Keq = 65
Initially 0.10 mole of O3 and 0.10 mole of O2 are placed in a 1.0 L container, Which of the following
describes the changes in concentrations as the reaction proceeds towards equilibrium?
[O3]
[O2]
A.
decreases
decreases
B.
decreases
increases
C.
increases
decreases
D.
increases
increases
17.
Consider the following equilibrium: 2CrO42-(aq) + 2H+(aq) ⇄ Cr2O72-(aq) + H2O(l)
yellow
orange
An unknown solution is added to an orange equilibrium system until the sample turns yellow. The solution
could be
A.
KNO3
B.
NaOH
C.
NH4NO3
D.
CH3COOH
18.
Consider the following equilibrium:
CH3COOH(aq) ⇄ CH3COO-(aq) + H+(aq) + heat
A stress was applied at time t1 and the data plotted on the following graph:
The stress imposed at time t1 is the result of
[H+]
time
A.
B.
C.
D.
19.
t1
the addition of HCl
decreasing the temperature
the addition of NaCH3COO
increasing the volume of the container
Consider the following potential energy diagram for an equilibrium system:
P.E.
Progress of the reaction
When the temperature of the system is increased, the equilibrium shifts to the
A.
left and the Keq increases
B.
left and the Keq decreases
C.
right and the Keq increases
D.
right and the Keq decreases
20.
Addition of a catalyst to an equilibrium system
A.
increases the value of the Keq
B.
increases the yield of the product
C.
has no effect on the rates of the reaction
D.
increases the rates of formation of both reactants and products
21.
Ammonia, NH3, is produced by the following reaction:
N2(g) + 3H2(g) 
2NH3(g) + energy
Which of the following would result in the highest concentration of ammonia at equilibrium?
A.
B.
C.
D.
increasing the temperature and increasing the pressure
decreasing the temperature and increasing the pressure
increasing the temperature and decreasing the pressure
decreasing the temperature and decreasing the pressure
22.
Consider the following equilibrium:
2NO2(g)  N2O4(g)
Keq = 1.15
The equilibrium concentration of NO2 is 0.50 mol/L. Calculate the equilibrium concentration of N 2O4(g).
A.
B.
C.
D.
23.
0.22 mol/L
0.29 mol/L
0.43 mol/L
0.58 mol/L
Consider the following equilibrium:
H2(g) + I2  2HI(g)
Keq = 50.0
What is the value Keq for the reaction rewritten as:
A.
B.
C.
D.
2HI(g)  H2(g) + I2(g)
-50.0
0.0200
25.0
50.0
Keq = ?
24.
Consider the following equilibrium: 2NOCl(g)  2NO(g) + Cl2(g)
A flask is filled with NOCl, NO, and Cl2(g). Initially there were a total of 5.0 moles of gases present. When
equilibrium is reached, there are a total of 8.0 moles of gases present. Which of the following explains the
observation?
A.
The reaction shifted left because the Trial Keq > Keq
B.
The reaction shifted left because the Trial Keq < Keq
C.
The reaction shifted right because the Trial Keq > Keq
D.
The reaction shifted right because the Trial Keq < Keq
25.
Consider the following equilibrium:
4NH3(g) + 5O2(g)  4NO(g) + 6H2O(g) + energy
Which of the following will cause the equilibrium to shift to the left?
A.
adding H2O(g)
B.
removing some NO(g)
C.
increasing the volume
D.
decreasing the temperature
A catalyst is added to a system already at equilibrium. How are the forward and reverse reaction rates
affected by the addition of the catalyst.
Forward Rate
Reverse Rate
A.
increases
increases
B.
increases
constant
C.
constant
decreases
D.
constant
constant
26.
27.
Consider the following equilibrium: 2NOBr(g)  2NO(g) + Br2(g) Keq = 0.064
At equilibrium, a 1.00 L flask contains 0.030 mole NOBr and 0.030 mole NO. How many moles of Br 2 are
present?
A.
0.0019
B.
0.064
C.
0.030
D.
0.47
28.
Which of the following does not apply to all chemical equilibrium systems
A.
They are closed.
B.
The macroscopic properties are constant
C.
Forward and reverse rates are equal
D.
There are equal concentrations of reactants and products
29.
The relationship between Ea and reaction rate is best represented as
A.
C.
30.
D.
The relationship between Keq and temperature for an exothermic reaction is best represented as
A.
C.
31.
B.
B.
D.
The relationship between reaction rate and temperature is best represented by
A.
C.
B.
D.
32.
The relationship between Ea and temperature is best represented by
A.
B.
D.
C.
32.
Methanol, CH3OH, can be produced by the following:
CO(g) + 2H2(g)  CH3OH(g) + energy
The conditions necessary to maximize the equilibrium yield of CH3OH are
A.
low temperature and low pressure
B.
high temperature and low pressure
C.
low temperature and high pressure
D.
high temperature and high pressure
33.
Consider the following equilibrium: 2NO(g) + O2(g)  2NO2(g) + energy
When the volume of the container is increased, the equilibrium shifts to the
A.
left and the Keq decreases
B.
right and the Keq increases
C.
left and the Keq remains constant
D.
right and the Keq remains comstant
34.
Consider the following reaction:
C3H8(g) + 5O2(g)  3CO2(g) + 4H2O(g)
ΔH = -2202 kJ
Which of the following applies to the forward reaction?
Entropy
Enthalpy
A.
increases
increases
B.
increases
decreases
C.
decreases
increases
D.
decreases
decreases
Subjective
1.
Consider the following equilibrium:
N2H4(g) + 2O2(g)  2NO2(g) + 2H2O(g)
More oxygen is added to the above equilibrium. After the system re-establishes equilibrium, identify the
substance(s), if any, that have a net
a)
increase in concentration
b)
decrease in concentration
2.
Given the following equilibrium:
H2(g) + I2(g)
 2HI(g)
Initially, 0.200 mole H2 and 0.200 mole I2 were placed into a 1.0 L container. At equilibrium, the [I2] is
0.040 M. Calculate the Keq.
3.
Consider the following equilibrium: 2CrO42-(aq) + 2H+(aq) ⇄ Cr2O72-(aq) + H2O(l)
yellow
orange
When HCl is added, the solution turns orange. Explain why this colour change occurs.
4.
Consider the following equilibrium system:
N2(g) + 3H2(g) 
2NH3(g) + energy
A 1.00 L container is filled with 7.0 mole NH3 and the system proceeds to equilibrium as indicated by the
graph.
8.0
M
6.0
4.0
2.0
NH3
a)
Draw and label the graph for N2 and H2. Fill in an ICE chart if you are not sure how to do
this.
N2(g) + 3H2(g) 
2NH3(g)
I
C
E
b)
Calculate the Keq for the above reaction.
5.
Consider the following equilibrium 2NO(g) + O2(g)  2NO2(g)
Keq = 1.5
0.800 mole NO, 0.600 moles O2, and 0.400 moles NO2 are placed in a vessel that 2.0 L. Show by
calculation that the reaction is not at equilibrium? What will happen to [O2] as equilibrium is approached?
6.
Consider the following equilibrium:
SO3(g) + NO(g)  NO2(g) + SO2(g) Keq = 0.500
Exactly 0.100 mole SO3 and 0.100 mole NO were placed in a 1.00 L flask and allowed to go to
equilibrium. Calculate the equilibrium concentration of SO2.