AP Chemistry Test (Chapter 13)
Multiple Choice (30%)
1)
Which one best describes the KC for this reaction?
3 A (aq) + 2 D (aq) + 5 C (s) <==> 3 B (aq) + 4 E (aq) + 2 G (ppt)
2)
A)
Kc =
[A]3[D]2
[E]4[D]2
B)
Kc = [B]3[E]4[G]2
[A]3[D]2[C]5
C)
Kc = [E]4[B]3
[A]3[D]2
D)
Kc = [A]3[D]2[C]5
[B]3[E]4[G]2
E)
None of these is correct
Please consider the gas phase reaction:
2 NH3 (g) <==> 3 H2 (g) + N2 (g)
∆H = +345 kJ/mol
Which one would decrease the yield of H2 ?
A)
C)
3)
High T & high P
High T & low P
B)
D)
Low T & low P
Low T & high P
AlBr3 dissolves in water, according to this mechanism:
AlBr3 (s) <==> Al+3 (aq) + 3 Br — (aq)
What effect would the addition of Na3PO4 have on this equilibrium?
A)
B)
C)
D)
E)
4)
Q becomes larger & the reaction creates more products.
Q becomes larger & the reaction creates more reactants.
Q becomes smaller & the reaction creates more products.
Q becomes smaller & the reaction creates more reactants.
There is no net effect on the equilibrium position.
Based upon the following information, which one is true about the reaction mixture?
2 NH3 (g) <==> N2 (g) + 3 H2 (g)
P (NH3) = 2.19 atm P (N2) = 4.33 atm
A)
B)
C)
D)
KP = 0.88
P (H2) = 0.72 atm
The product concentrations are too high & the reaction will shift left to establish
equilibrium.
The product concentrations are too high & the reaction will shift right to establish
equilibrium.
The reactant concentrations are too high & the reaction will shift right to establish
equilibrium.
The reactant concentrations are too high & the reaction will shift left to establish
equilibrium.
5)
Which one will occur if the volume of the container is decreased.
2 A (l) + 5 B (g) <==> 2 C (g) + 4 D (ppt) + 2 E (g)
A)
B)
C)
D)
E)
6)
The mass of A will remain constant.
The temperature will decrease.
The partial pressure of B will increase.
The mass of D will increase.
None of these
Consider the gaseous equilibrium: 2 A ↔ B + 3 C.
Determine the value of the missing [C] at equilibrium.
Experiment #
1
2
A)
C)
E)
7)
∆H = +545 kJ/mol rxn
Kp = 35.2
[A] at equilibrium
0.15 M
0.25 M
0.32 M
0.13 M
None of these are correct.
[B] at equilibrium
0.30 M
0.20 M
B)
D)
[C] at equilibrium
0.20 M
???
0.033 M
0.70 M
Which one is false about this graph?
D
[M]
E
Time
A)
B)
C)
D)
E)
8)
The reaction is spontaneous in the forward direction.
The reaction is product favored at equilibrium.
Kc > 1
E <==> D
None of these are false.
If this system is at equilibrium in a closed vessel and a small amount of HN3 is added, which
one would NOT happen?
HN3 (g) + 2 H2O (l) <==> N2H4 (g) + HNO2 (g)
A)
B)
C)
D)
E)
∆H = –545 kJ/mol rxn
The partial pressure of HNO2 would increase to re-establish equilibrium.
The partial pressure of HN3 would decrease to re-establish equilibrium.
Some N2H4 would form to re-establish equilibrium.
The inside of the flask would have water droplets forming on it.
The temperature would increase.
9)
KC = 1.05 X 104 for this reaction: 2 Fe3+ (aq) + 3 S2– (aq) <==> Fe2S3 (ppt)
The concentration of Fe3+ in equilibrium with 0.201 M S2– is _____.
A)
C)
E)
10)
9.23 M
0.0118 M
None of these are correct.
B)
D)
0.0218 M
0.108 M
If the reaction flask is placed into an ice water bath, which one will occur?
2 A (g) + 3 B (g) <==> C (g) + 4 D (s) + E (g) ∆H = +671 kJ/mol rxn
A)
B)
C)
D)
E)
11)
The total pressure in the flask will increase.
The molarity of C will increase.
The partial pressure of A will decrease.
The mass of D will remain constant.
None of these will occur.
Please consider the following process. Which one is true?
Reactants < == > Products
A)
B)
C)
D)
E)
12)
Kc1 = 1/Kc2
Kc1 = –Kc2
Kc1 = Kc2
Kc1 = (Kc2)2
No relationship exists between Kc1 and Kc2.
Please choose all that will cause a decrease in Kc.
I)
II)
III)
IV)
A)
C)
E)
13)
Kc1 = Kc in forward reaction progress.
Kc2 = Kc in reverse reaction progress.
Heating an exothermic reaction.
Heating an endothermic reaction.
Placing a reaction with –∆H in an ice bath.
Placing a reaction with +∆H in an ice bath.
II, III
I, II, III, IV
II, IV
B)
D)
I, IV
I, III
Please consider this reaction.
4 PBr3 (g) + 6 Cl2 (g) <==> 4 PCl3 (g) + 6 Br2 (g)
What is the Kp for this reaction?
2 PCl3 (g) + 3 Br2 (g) <==> 2 PBr3 (g) + 3 Cl2 (g)
A)
C)
E)
0.100
10.0
None of these are correct.
B)
D)
0.447
2.24
Kp = 0.200
14)
Which one is an example of a chemical or physical process with Kc < 1 at 1 atm.
A)
C)
15)
A match burning.
Water boiling at 100oC.
B)
D)
Ice melting at – 10oC.
Leaves growing in the summer.
Please choose all that apply to a nonspontaneous reaction.
I)
II)
III)
IV)
A)
C)
E)
Kc > 1 for the reverse reaction.
Kc < 1 for the forward reaction.
The concentrations of products are greater than the reactants at equilibrium.
The concentrations of reactants are greater than the products at equilibrium.
IV
B)
I, II, III
D)
None of these choices apply.
III
I, II, IV
Problems (70%)
1)
2 NaHCO3 (s) <===> Na2CO3 (s) + H2O (g) + CO2 (g)
A 200.0-g sample of solid NaHCO3 was placed in a previously evacuated rigid
8.00-liter container and heated to 160.0 °C. Some of the original solid remained and the total
pressure in the container was 4.46 atmospheres when equilibrium was reached.
2)
3)
a)
How many grams of the original solid remained in the container?
b)
Write the equilibrium expression for the equilibrium constant, K p, and calculate its value.
N2O4 (g) <===> 2 NO2 (g)
a)
At a temperature of 342 K, 1.25 mole of gaseous N2O4 is placed in a 4.00-liter flask, and
equilibrium for the reaction is attained when 15.00 % of the N 2O4 has decomposed. Write
the equilibrium expression and calculate the value of the equilibrium constant K c for the
reaction.
b)
What is Kp for the reverse reaction at 342 K?
c)
At the same temperature, 0.52 mole NO2 and 0.10 mole N2O4 are placed in a different 4.00liter flask. When equilibrium is established, is there more of less than 0.10 mole N2O4
present? Justify your answer.
2 Au3+ (aq) + 3 SO42– (aq) < == > Au2(SO4)3 (ppt)
Kc = 8.00 X 103
a)
When enough solid Au2(SO4)3 is added to 1.00 L of water to form a saturated solution, what
will be the concentrations of Au3+ and SO42– ?
b)
What will happen to the concentration of Au3+ when a solution of Pb(NO3)2 is slowly poured
into the 1.00-L flask at equilibrium? Please support your answer.
4)
2 HCl (g) < == > H2 (g) + Cl2 (g)
Kp = 2.70
A 2.00-L flask at 315 K is injected with 1.00 atm HCl.
5)
a)
What is the partial pressure of HCl at equilibrium?
b)
How many moles of HCl decomposed?
Please add to the graph on the answer sheet what would occur if F2 is removed from the
reaction flask after equilibrium was reached.
O2 (g) + 2 F2 (g) <==> 2 OF2 (g)
Test (Chapter 13)
Name______________________________________
1)
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6)
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11)
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2)
_____
7)
_____
12)
_____
3)
_____
8)
_____
13)
_____
4)
_____
9)
_____
14)
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5)
_____
10)
_____
15)
_____
[O2] and [F2]
5)
F2 is removed.
O2 is added.
[OF2]
Time