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40S Chemistry
Student – Equilibrium Unit
Equilibrium
1
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40S Chemistry
Student – Equilibrium Unit
EQUILIBRIUM OUTCOMES
All important vocabulary is in Italics and bold.
C12-4-01:
Relate the concept of equilibrium to physical and chemical systems.
Include: conditions necessary to achieve equilibrium.
C12-4-04:
Write equilibrium law expressions from balanced chemical equations and solve problems
involving equilibrium constants.
Include: ICE tables.
C12-4-03:
Use the value of the reaction quotient, Q to explain how far a system at equilibrium has gone
towards completion.
C12-4-11:
Write solubility product (Ksp) expressions from balanced chemical equations for salts with low
solubility and solve related problems.
C12-4-06:
Use Le Chatelier’s principle to predict and explain shifts in equilibrium.
Include: Interpret concentration versus time graphs.
C12-4-09
Describe some practical applications of Le Chatelier’s principle.
Additional KEY Terms
Closed system
Macroscopic
Saturated
Ionization
Dissociation
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Student – Equilibrium Unit
40S Chemistry
EQUILIBRIUM EXPRESSIONS AND THE CONSTANT
C12-4-01:
Relate the concept of equilibrium to physical and chemical systems.
1. Write the equilibrium expressions (mass action expression) for each of the following reactions:
a. SO2(g) + NO2(g)
c. 3 O2(g)
SO3(g) + NO(g)
2 O3(g)
d. MgCO3(s)
e. 2 Bi3+(aq) + 3 H2S(g)
g. Cl2(g) + PCl3(g)
i. 2 NO2(g)
2 Bi2S3(s) + 6 H+(aq)
PCl5(g)
2 NO(g) + O2(g)
k. Cl2(g) + PCl3(s)
b. 2 C(s) + 3 H2(g)
f. I2(aq)
C2H6(g)
CO2(g) + 2 MgO(s)
I2(s)
h. I2(g) + Cl2(g)
j. 2 SO2(g) + O2 (g)
2 ICl(g)
2 SO3(g)
PCl5(g)
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40S Chemistry
Student – Equilibrium Unit
2. Comment on the favorability of product formation in each of the reactions.
a. H2(g) + F2(g)
b.
2 HF(g)
SO2(g) + NO2(g)
c. 2 H2O(g)
NO(g) + SO3(g)
2 H2(g) + O2(g)
KC = 1.0 ×1013
KC = 1.0 ×102
KC = 6.0 ×10–28
3. Chemists have determined the equilibrium constants for several reactions. In which of these reactions are
the products favoured over the reactants?
a. KC = 1.0×102
b. KC = 3.5
c. KC = 0.003
d. KC = 6.0 ×10–4
4. Give an example of physical equilibrium you encounter in daily life and explain it briefly.
5. What are the conditions necessary for a system to reach equilibrium and what signs are there that
equilibrium has been reached?
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40S Chemistry
Student – Equilibrium Unit
EQUILIBRIUM EXPRESSIONS AND THE CONSTANT (TYPE I AND II)____________
C12-4-04:
Write equilibrium law expressions from balanced chemical equations and solve problems
involving equilibrium constants.
1. The formation of ammonia from hydrogen and nitrogen occurs by the reaction below:
3 H2 (g) + N2 (g) ↔ 2 NH3 (g)
Analysis of an equilibrium mixture of nitrogen, hydrogen, and ammonia contained in a 1.00 L flask at 300.0°C
gives the following results: hydrogen 0.150 moles; nitrogen 0.250 moles: ammonia 0.100 moles. Calculate KC
for the reaction. (11.9)
2. A mixture at equilibrium at 827°C contains 0.552 moles of CO2, 0.552 moles H2, 0.448 moles CO, and
0.448 moles of H2O in a 1.00 L container. What is the Kc constant? (0.659)
CO2 (g) + H2 (g) ↔ CO (g) + H2O (g)
3. The equilibrium constant for the reaction at 755°C is 0.256.
4 H2 (g) + CS2 (g) ↔ CH4 (g) + 2 H2S (g)
What is the equilibrium concentration of H2S if at equilibrium [CH4] = 0.00108 mol/L, [H2] = 0.316 mol/L,
[CS2] = 0.0898 mol/L? (0.461)
4. Find the value of K if at equilibrium there is 25.0 moles of P4, 10.0 moles of H2 and 5.00 moles of PH3, in a
5.00 L container. The equation is
(0.00313)
P4 (g) + 6 H2 (g) ↔ 4 PH3 (g)
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40S Chemistry
Student – Equilibrium Unit
5. Find the value of K for the equilibrium system
ZnO (s) + CO (g) ↔ Zn (s) + CO2 (g)
If at equilibrium there are 3.0 moles of CO, 4.0 moles of Zn and 4.0 moles of CO2 in a 500.0 mL container.
(1.3)
6. If K = 46.0 for
H2 (g) + I2 (g) ↔ 2 HI (g)
What [I2] would be in equilibrium with 0.50 mol/L HI and 0.10 mol/L H2? (0.054)
7. If K = 10.0 for
N2 (g) + 3 H2 (g) ↔ 2 NH3 (g)
How many moles of NH3, at equilibrium, will be in a 2.00 L container if [H2] is 0.600 mol/L and [N2] is 0.100
mol/L? (0.930)
8. Ammonia is produced according:
3 H2 (g) + N2 (g)  2 NH3 (g)
What is the value of K if at equilibrium a 3.0 L flask contains 0.45 mol of hydrogen, 0.75 mol of nitrogen,
and 0.30 mol of ammonia? (12)
9. Given the reaction:
N2 (g) + O2 (g)  2 NO (g)
An analysis of the equilibrium mixture in a 5.0 L flask gives the following results; 2.5 mol of oxygen, 3.5
mols of nitrogen, and 0.5 mol of nitrogen monoxide. What is the value of Kc? (0.029)
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40S Chemistry
Student – Equilibrium Unit
10. In a closed container, nitrogen and hydrogen react to produce ammonia. At equilibrium the [N2] = 2.0 x 10 4
M, [H2] = 4.0 x 10 -3 M, [NH3] = 2.2 x 10 -4 M. What is the Kc for the reaction? (3800)
N2 (g) + H2 (g)  NH3 (g)
11. For the given reaction of methanol, the equilibrium concentrations were found to be [CO] = 0.170 M, [H2] =
0.322, [CH3OH] = 0.0406. Find the value of Kc. (0.431)
CH3OH (g)  CO (g) + 2 H2 (g)
12. Bromine chloride, BrCl, decomposes to form bromine and chlorine.
2 BrCl (g) ↔ Cl2 (g) + Br2 (g)
At a certain temperature the equilibrium constant for the reaction is 11.1, and the equilibrium mixture contains
4.00 mol of Cl2. How many moles of Br2 and BrCl are present in the equilibrium mixture? (1.20)
13. The decomposition of hydrogen iodide to hydrogen and iodine occurs by the reaction
2 HI (g) ↔ H2 (g) + I2 (g)
Hydrogen iodide is placed in a container at 450°C an equilibrium mixture contains 0.50 moles of hydrogen
iodide. The equilibrium constant is 0.020 for the reaction. How many moles of iodine and hydrogen are present
in the equilibrium mixture? (0.071)
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40S Chemistry
Student – Equilibrium Unit
EQUILIBRIUM EXPRESSIONS AND THE CONSTANT (TYPE III)_________________
C12-4-04:
Write equilibrium law expressions from balanced chemical equations and solve problems
involving equilibrium constants.
1.
For the gas reaction A + B  AB , initially 1.0 mol of A and 1.0 mol of B were placed in a 1.0 L
container. At equilibrium, the concentration of AB was 0.40 M.
a) Determine the value of the equilibrium constant.
b) What is the AB concentration if [A] = 1.2 M and [B] = 0.27 M?
c) What is [A] if [B] = 1.7 M and [AB] = 2.0 M?
(1.1, 0.36, 1.1)
2.
Consider the reaction:
CO2 (g) + H2 (g)  CO (g) + H20 (g)
Initially, 0.25 mol of water vapour and 0.20 mol of carbon monoxide are placed in a 1.00 L reaction
vessel. At equilibrium, evidence shows that 0.10 mol of carbon dioxide is present. Calculate the Kc for
the reaction. (1.5)
3.
Consider the reaction:
2 AB (g)  A2 (g) + B2 (g)
4.0 mol of AB were placed in a 2.0 L flask and were allowed to reach equilibrium. At equilibrium, it
was observed that 1.0 mol of A2 was present. What is the value of Kc? (0.25)
4.
Initially, 0.10 mol of NO and 0.050 mol of H2, and 0.10 mol of H20 are placed in a 1.0 L container and
allowed to react. At equilibrium the [NO] = 0.062 M. Calculate the equilibrium constant, K.
(Kc = 650)
2
5.
NO (g) + 2 H2 (g)  N2 (g) + 2 H20 (g)
In a 1 L heated reaction vessel the following concentrations were added, [SO2] = 2.0 M, [NO2] = 2.0 M.
At equilibrium, [NO] = 1.3 M. Find the Kc. (3.5)
SO2 (g) + NO2 (g)  SO3 (g) + NO (g)
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6.
Student – Equilibrium Unit
40S Chemistry
Given the following reaction:
2 NH3 (g)  N2 (g) + 3 H2 (g)
4.0 mol of NH3 were added to a 2.0 L flask. At equilibrium there were 2.0 mol present. Find the
equilibrium concentrations for the other entities and solve for the equilibrium constant. (1.7)
7.
Given the reaction:
H2 (g) + I2 (g)  2 HI (g)
One mole of hydrogen and one mole of iodine are placed in a one litre container and allowed to react.
What is the value of K at equilibrium if 1.36 mols of HI are present? (18.06)
8.
For the gas reaction: A + B  2 C , 0.50 mol of each A and B are placed in a 1 L container and
allowed to reach equilibrium. Equilibrium concentration of C = 0.0235 M. Determine the value of Kc .
(0.002)
9.
Initially, enough ammonia was dissolved in water to make a 0.0124 M solution. This was left at 25ºC to
reach equilibrium, at which time it was found that the [OH -] = 4.64 x 10 -4 M. Calculate the remaining
concentrations at equilibrium and find the value of Kc.
(0.0119, 4.64 x 10 -4, 1.81 x 10 -5)
NH3 (g) + H2O(l)  NH4+ (g) + 0H- (g)
10.
Initially, 12.0 mol of SO3 was added to a 3.0 L reaction vessel. At equilibrium there were 3.0 mol of
SO2 present. Find the value of Kc and the remaining equilibrium concentrations. (0.056)
2 SO3 (g)  2 SO2 (g) + O2 (g)
11.
Initially the concentrations of N2 and O2 are 1.8 mol/L each and there is no NO. If at equilibrium the
[NO] is 2.0 mol/L, find K. (6.25)
N2(g) + O2(g)
12.
2 NO(g)
Find K for the reaction
2 CO(g) + O2(g)
2 CO2(g)
If initially, there is 5.0 moles of CO, 10.0 moles of O2 and 1.0 mole of CO2 in a 2.0 L container and at
equilibrium CO2 has a concentration of 2.5 mol/L. (6.25)
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Student – Equilibrium Unit
40S Chemistry
EQUILIBRIUM EXPRESSIONS AND REACTION QUOTIENT__________ _______
C12-4-03:
-
Use the value of the reaction quotient, Q to explain how far a system at equilibrium has gone
towards completion.
Remember, calculate Q just like you would Kc:
1. A vial contains 0.150 M of NO2 and 0.3 M N2O4. Calculate the Q of the reaction. (13.3)
2 NO2 (g)  N2O4 (g)
2. For the reaction: A (s) + 2 B (g)  2 C (g)
Kc = 25.0
[A] = 12.0 mol/L [B] = 2.0 mol/L [C] = 30.0 mol/L
a) Is the system at equilibrium.
b) Which reaction needs to be faster (favoured), forward or reverse?
c) Which concentrations are increasing or decreasing?
3. At 448 ºC, Kc = 50.5 for the reaction,
H2 (g) + I2 (g)

2 HI (g)
Find the Q and predict how the reaction proceeds if the concentration of hydrogen is 0.15 M, 0.175 M
for Iodine, and 0.950 for hydrogen iodide. (34.4, right)
4. At a given temperature, the K = 0.055 for the reaction that follows:
(0.55, left)
PCl5 (g) +  PCl3 (g) + Cl2 (g)
Find Q and predict how the reaction proceeds if [PCl5] = 0.8 M, [PCl3] = 0.2 M, and [Cl2] = 2.20 M.
5. At 753 ºC, Kc = 0.0060 for the decomposition of calcium carbonate, which is described by the following
equation:
CaCO3 (s)  CaO (s) + CO2 (g)
Find Q and predict how the reaction will proceed if [CO2] = 0.0004 M.
(0.0004)
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Student – Equilibrium Unit
40S Chemistry
6. For the reaction: CO (g) + H2O (g)  CO2 (g) + H2 (g)
If Kc = 5.10 at 527ºC, and [CO] = 0.15 M, [H2O] = 0.25 M, [H2] = 0.42 M and [CO2] = 0.37 M,
calculate Q and determine how the reaction will proceed. (4.1)
7. Given the following equation:
2 HI (g) 
H2 (g) + I2 (g)
Kc = 0.020
Is the system at equilibrium in each of the following cases? If not, predict the direction in which the
reaction will proceed to reach equilibrium.
(0.02, 0.34)
a) [HI] = 0.14 M, [H2] = 0.04 M, [I2] = 0.01 M
b) [HI] = 0.20 M, [H2] = 0.15 M, [I2] = 0.09 M
8. Given the equilibrium system:
PCl5 (g) +  PCl3 (g) + Cl2 (g)
Kc = 12.5 at 60ºC
The contents of a 1.0 L reaction vessel is analyzed and found to contain 3.2 mol of Cl2, 1.5 mol of PCl3,
and 2.0 mol of PCl5. Show that the reaction mixture has not yet reached equilibrium. (2.4)
9. There exists an equilibrium if 5.0 moles of CO2, 5.0 moles of CO and 0.20 moles of O2
are in a 2.0 L container at 562°C. Find Kc for the reaction
2 CO (g) + O2 (g)  2 CO2 (g)
Would the system be at equilibrium if [CO2] = 15.8 mol/L, [CO] = 10.0 mol/L and
[O2] = 0.25 mol/L? If not, which reaction is favoured?
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10. For the reaction:
Student – Equilibrium Unit
40S Chemistry
4 NH3 (g) + 7 O2 (g)  4 NO2 (g) + 6 H2O (g)
Equilibrium is reached when [H2O] = 0.100 mol/L, [O2] = 2.00 mol/L, [NO2] = 0.200 mol/L and [NH3]
= 0.500 mol/L.
If 0.75 moles of H2O, 12.0 moles of NO2, 30.0 moles of O2 and 0.30 moles of NH3 are in a 3.0 L
container at the same temperature, is equilibrium achieved? If not, which reaction is favoured?
-
Complete as a Type III question first to get concentrations, then determine Qc and compare to given Kc:
11. For the reaction: 2 SO2 (g) + O2 (g)  2 SO3 (g)
Kc = 16.0
Initially, [SO2] = 5.0 mol/L, [O2] = 10.0 mol/L and [SO3] = 0.
After two hours [O2] = 7.9 mol/L. Is the system at equilibrium? If not, which substances
are increasing and which are decreasing?
12. Keq = 46.0 for the reaction
H2 (g) + I2 (g)  2 HI (g)
Initially there are 6.90 moles of H2 and 2.40 moles of I2 in a 1.00 L container. After 5
hours there is still 1.00 moles of I2 left. Is the system at equilibrium? If not, which
substances are increasing and which are decreasing?
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40S Chemistry
Student – Equilibrium Unit
SOLUBILITY EQUILIBRIA_______________________________________________
C12-4-11:
Write solubility product (Ksp) expressions from balanced chemical equations for salts with low
solubility and solve related problems.
1.
Write the dissociation equation and the solubility product expression for each of the
following (assume that all the solid that dissolves exists as ions).
a. PbSO4
d. SrCO3
b. Al2(SO4)3
e. Ag2CO3
c. Ba(OH)2
f. Fe2(SO4)3
2.
From the following solubilities, calculate the Ksp. ** (watch units)
a. Ca3(PO4)2
7.15 x 10-7 M
c. AgI
2.88 x 10–6 g/L
–6
b. Pb(OH)2
4.20 x 10 mol/L
d. CaF2
1.70 x 10-5 g/mL
3.
A saturated solution of calcium hydroxide has an hydroxide ion concentration of
3.0 x 10-3 mol/L. Calculate the Ksp of calcium hydroxide.
4.
At 25°C, a saturated solution of iron (III) hydroxide has an iron ion concentration
of 1.3 x 10-13 mol/L. Calculate the Ksp of iron (III) hydroxide.
5.
If 6.7 x 10-5 g of AgBr is all that can be dissolved at 25°C in 500.0 mL, calculate
the solubility product of AgBr.
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40S Chemistry
Student – Equilibrium Unit
6.
If [D+] is 2.00 x 10 -5 M at equilibrium, what is the Ksp for D2A?
7.
Given the following compounds’ Ksp, calculate their solubilities in mol/L and g/L.
a. CuS
Ksp = 6.31 x 10–36
c. SrC2O4
Ksp = 1.58 x 10–7
–8
b. PbI2
Ksp = 1.39 x 10
d. Al(OH)3
Ksp = 1.26 x 10–33
8.
What are the equilibrium concentrations of all the ions in a saturated solution of
AgSCN at 25°C, if the Ksp is 1.6 x 10-14?
9.
What are the equilibrium concentrations of all the ions in a saturated solution of
Cu(OH)2 at 25°C, if the Ksp is 1.6 x 10-19.
10.
How many grams of each compound should be added to a 1.0 L container to have a saturated aqueous
solution?
a. Lead (II) sulfate, PbSO4
Ksp = 1.3 x 10 -8
b. Silver carbonate, Ag2CO3
Ksp = 6.2 x 10 -12
c. Magnesium hydroxide, Mg(OH)2
Ksp = 1.2 x 10 -11
ANSWERS
2 a) 2.02 x 10-29
b) 2.96 x 10-16
c) 1.50 x 10-16
d) 4.12 x 10-11
-8
-51
-13
3) 1.35 x 10
4) 7.7 x 10
5) 5.1 x 10
6) 4.0 x 10-15
7 a) 2.51 x 10-18 M, 2.40 x 10-16 g/L
b) 1.5 x 10-3 M, 0.698 g/L
-4
-2
c) 3.97 x 10 M, 6.97 x 10 g/L
d) 2.61 x 10-9 M, 2.04 x 10-7 g/L
8) 1.3 x 10-7 M
9) 3.4 x 10-7 M, 6.8 x 10-7 M
10) 0.0345g, 0.0317g, 0.00835g
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LeCHATELIER’S PRINCIPLE AND STRESS______
C12-4-06:
Student – Equilibrium Unit
40S Chemistry
_________________________
Use Le Chatelier’s principle to predict and explain shifts in equilibrium.
1. For the reaction: PCl3(g) + Cl2(g)  PCl5(g)
H = -92.5 kJ
Predict the effect on the position of the equilibrium that results from
a) increasing the total pressure by decreasing volume.
b) injecting more Cl2 gas.
c) increasing the temperature.
d) increasing the volume of the container.
e) adding a catalyst.
2. For the reaction: CH4(g) + H2O(g) + 49.3 kJ  CO(g) + 3 H2(g)
Predict the effect on the position of the equilibrium that results from
a) increasing temperature.
b) decreasing temperature.
c) decreasing the pressure.
d) decreasing the volume of the container.
e) adding a solid drying agent such as CaCl2 which reacts with H2O(g).
3. For the reaction: 9.4 kJ + 2 HI(g)  H2(g) + I2(g)
a) What is the effect on [HI] if a small amount of H2 is added?
b) What is the effect on [HI] if the pressure of the system is increased?
c) What is the effect on [HI] if the temperature is increased?
d) What is the effect on [HI] if a catalyst is added?
4. For the reaction: CO(g) + 2 H2(g)  CH3OH(g) + energy
Predict the effect of the following changes on the equilibrium concentration of CH3OH(g)
a) a decrease in temperature.
b) an increase in pressure.
c) addition of H2(g).
d) addition of a catalyst.
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5. In the equilibrium reaction:
40S Chemistry
Student – Equilibrium Unit
2 NO(g) + O2(g)  2 NO2(g) + 114.6 kJ
What will be the change in the equilibrium [NO2] under each of the following conditions?
a) O2 is added.
b) NO is removed.
c) energy is added.
6. For the following reaction:
N2O4(g) + 58.9 kJ  2 NO2(g)
How will the equilibrium [NO2] be affected by the following?
a) an increase in pressure.
b) an increase in temperature.
c) the addition of a catalyst.
7. Suggest 4 ways to increase the [SO3] in the following equilibrium reaction:
2 SO2(g) + O2(g)  2 SO3(g) + 192.3 kJ
8. For the reaction: 4 HCl(g) + O2(g)  2 H2O(g) + 2 Cl2(g) + 114.4 kJ
EXPLAIN how each of the following effect the position of the equilibrium.
a) the size of the container is increased.
b) energy added.
c) O2(g) added.
d) HCl(g) removed.
e) Adding a catalyst
9. Nitric oxide gas, NO, releases 57.3 kJ/mol when it reacts with oxygen gas to give
nitrogen dioxide gas.
a) Write the equation for this reaction.
b) Predict the effect that increasing the temperature will have on
i) the equilibrium concentrations.
ii) the speed of formation of NO2.
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40S Chemistry
LeCHATELIER’S PRINCIPLE AND STRESS______
C12-4-06:
Student – Equilibrium Unit
_________________________
Use Le Chatelier’s principle to predict and explain shifts in equilibrium.
Include: Interpret concentration versus time graphs.
The above graph shows concentration versus time for a system containing carbon
monoxide (CO) dichlorine (Cl2) and phosgene (COCl2).
1. Write a balanced equation to represent the reaction studied.
2. How much time was required for the system to reach equilibrium?
3. Calculate an approximate value for the equilibrium constant Kc using the concentrations at time t = 60 s.
4. Explain the changes 70 s after the initiation of the reaction.
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40S Chemistry
Student – Equilibrium Unit
5. What changes in conditions might have been imposed on the system 120 s after the initiation of the
reaction?
6. Are any events taking place between the interval 50 s and 70 s? between 280 s and 300 s? Explain your
answers.
7. What changes may have taken place at t = 320 s?
8. What differences would you have noticed if a catalyst had been present during the entire course of this
reaction?
9. List the changes you might impose on this system if you wanted to produce a maximum amount of
phosgene (COCl2)?
10. Calculate the equilibrium constant for t = 100s, 300s and 500s. How could you account for the differences in
the value calculated for the equilibrium constant Kc from the concentrations at different time points on the
graph?
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40S Chemistry
Student – Equilibrium Unit
EQUILIBRIUM UNIT REVIEW____________________________________________
1. If 1.0 mol each of carbon dioxide and hydrogen is initially injected into a 10.0 L reaction chamber at 986ºC,
what would be the concentrations of each entity at equilibrium?
(Kc = 1.60) (0.044, 0.044, 0.056, 0.056)
CO2 (g) + H2 (g)  CO (g) + H20 (g)
2. Consider the reaction:
2 HBr (g)  H2 (g) + Br2 (g)
Initially, 0.25 mol of hydrogen and 0.25 mol of bromine are placed in 500 mL reaction vessel and
heated. The Kc for the reaction is 0.020. Calculate the concentrations at equilibrium. (0.78, 0.11, 0.11)
3. With reference to the equation:
2 SO2 (g) + O2 (g)  2 SO3 (g)
(endothermic)
a. What stresses will produce an increase in the quantity of SO3 produced, if the temperature is kept
constant?
b. What is the effect of a rise of temperature on the equilibrium?
4. Hydrogen peroxide can be decomposed as follows:
H2O2 (l)  H2 (g) + O2 (g)
(exothermic)
Equilibrium is established in a 10 L flask at room temperature. Predict the direction of the equilibrium
shift.
a. hydrogen gas is added to the flask.
b. The temperature is raised to 500 ºC.
c. The entire mixture is compressed into a smaller volume.
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Student – Equilibrium Unit
40S Chemistry
5. For the given reaction of methanol, the equilibrium concentrations were found to be [CO] = 0.170 M, [H2] =
0.322, [CH3OH] = 0.0406. Find the value of Kc. (0.434)
CH3OH (g)  CO (g) + 2 H2 (g)
6. Write the equilibrium constant expression for the following chemical reaction:
H2 (g) + Cl2 (g)  2 HCl (g)
7. At 448 ºC, Kc = 50.5 for the reaction,
H2 (g) + I2 (g)

2 HI (g)
Find the Q and predict how the reaction proceeds if the concentration of hydrogen is 0.15 M, 0.175 M for
Iodine, and 0.950 for hydrogen iodide. (34.4)
8. Define, in detail, the following terms: closed system, equilibrium, dynamic equilibrium,
Le Chatelier’s principle.
9. For the all-gas reaction of N2 + O2  2 NO, the equilibrium constant is 1.0 x 10 -30 at room
temperature, and then 0.1 at 2000ºC. Which reaction, the forward or reverse,
a. Is favor at room temperature?
b. Is favored at the higher temperature?
c. is the forward reaction endothermic or exothermic? Explain.
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40S Chemistry
Student – Equilibrium Unit
10. One liter of water is able to dissolve 2.5 x 10 -3 mol of PbF2. What is the Ksp for this compound?
(6.2 x 10-8)
11. The Ksp of PbI2 is 8.3 x 10 -9. What is the molar solubility of this compound in water?
(1.28 x 10-3 mol/L)
12. Arrange the following ionic solids in order of decreasing solubility at room temperature, on the basis of their
Ksp values:
a. BaCO3 = 2 x 10 -9
b. CaCO3 = 5 x 10 -9
c. MgCO3 = 2 x 10 -8
d. PbCO3 = 7.4 x 10 -14
13. A saturated aqueous solution of barium sulfate, BaSO4, a slightly soluble ionic compound has added to it a
few crystals of sodium sulfate, which is readily soluble in water.
a. In terms of a shift in the position of equilibrium, describe what happens when the sodium sulfate
is added to the solution.
b. How will this shift affect the concentration of barium and sulfate ions?
c. How will this shift affect the mass of BaSO4?
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