CHEM 1332 SUMMER 2005
TEST 2 VERSION 1
NO CHEATING!
BUBBLE IN “1” IN THE P COLUMN TO GET YOUR GRADE POSTED!!!!! [the only way you’ll find out how you did!]
1.
Which of the following statements is FALSE?
(A)
(B)
(C)
(D)
(E)
A reaction is at equilibrium when the forward and reverse reactions occur at the same rate.
At equilibrium, the concentrations of all species present are constant.
Even though a reaction at equilibrium appears to have stopped, reactions are still taking place.
The equilibrium position depends upon the quantity of the starting materials.
The equilibrium position depends upon the temperature of the reaction.
2.
The gaseous reaction, 3 A + 6 B ∆ 3 C + 3 D has an equilibrium constant of 0.125. What is the value of the equilibrium constant for
the reaction, C + D ∆ A + 2 B?
(A)
0.00195
3.
The reaction, NH4SH(s) ∆ NH3(g) + H2S(g) has an equilibrium constant, Kc, of 7 at 313 K. If a mixture consisting of 1.5 moles of
NH4SH, 3.0 moles of NH3 and 3.0 moles of H2S in a 1 liter container is taken then:
(A)
(B)
(C)
(D)
(E)
The reaction is at equilibrium
The value of Q is 6 and the reaction goes to the right in order to reach equilibrium
The value of Q is 6 and the reaction goes to the left in order to reach equilibrium
The value of Q is 9 and the reaction goes to the left in order to reach equilibrium
The value of Q is 9 and the reaction goes to the right in order to reach equilibrium
4.
For which of the following equilibria does Kp = Kc?
(A)
(C)
(E)
C(s) + CO2(g) ∆ 2 CO(g)
2 H2(g) + O2(g) ∆ 2 H2O(g)
N2(g) + O2(g) ∆ 2 NO(g)
(B)
0.125
(C)
0.5
(B)
(D)
1
(D)
2
Cl2(g) ∆ 2 Cl(g)
CH4(g) + H2O(g) ∆ CO(g) + 3 H2(g)
(E)
512
5.
At a given temperature, the equilibrium constant (Kc) for the reaction, 2 HCl(g) ∆ H2(g) + Cl2(g) is 12.5. When a given quantity of
HCl is introduced into a 1.00 liter container, the equilibrium concentration of HCl is 1.25 moles/liter. What is the equilibrium
concentration of H2(g)?
(A)
(D)
4.42 moles/liter
0.2 moles/liter
6.
Starting with 0.0350 M COCl2, calculate the equilibrium constant (Kc) for the reaction, COCl2(g) ∆ CO(g) + Cl2(g), if the
equilibrium concentration of CO is 0.0232 M.
(A)
1.54 x 10-2
7.
At 25.0 ºC, the reaction N2O4(g) ∆ 2 NO2(g) has an equilibrium constant, Kc, of 0.113. Calculate the concentration of NO2 at
equilibrium when 2.5 moles of N2O4 are placed into a 1.00 liter container.
(A)
(D)
0.532 moles/liter
0.266 moles/liter
8.
The reaction, CaSO3(s) ∆ CaO(s) + SO2(g), has a ∆Hº value of -150 kJ at 250 ºC. Which of the following would reduce the amount
of the poisonous gas, SO2, present at equilibrium.
(A)
(C)
(E)
Adding lots of CaO
Performing the reaction in a large volume container
Adding an appropriate catalyst
9.
Which of the following substances would NOT be considered to be amphiprotic in water?
(A)
H2O
10.
The Kw of water at 90 ºC is 1.0 x 10-12. At this temperature:
(A)
(B)
(C)
(D)
Water is acidic because the [H3O+] in pure water is 1 x 10-6 and so the pH is 6
0.1 M HCl will have a pH of less than 1.
pH + pOH = 12
The pH of 1 M NaOH would be 14 which is bigger than 12 so 1 M NaOH cannot exist at 90 ºC.
(B)
(E)
(B)
4.56 x 10-2
(B)
(E)
(B)
0.625 moles/liter
0.1 moles/liter
HCO3-
(C)
(C)
1.97
0.252 moles/liter
0.956 moles/liter
(C)
(B)
(D)
(C)
(D)
NH3
2
0.3125 moles/liter
21.9
(E)
65.0
0.504 moles/liter
Removing CaSO3 as it is formed
Performing the reaction at high temperatures
(D)
H2PO4-
(E)
HSO3-
(E)
None of these are correct.
3
11.
Calculate the pH of 1.0 x 10-8 M HCl.
(A)
(D)
8
slightly less than 7
12.
An new weak acid, CH3CH2C(OH)2CH2C(OH)2CH2COOH is synthesized and a 0.1 M solution is found to have a pH of 3.50. What
is the Ka of the new acid?
(A)
3.17 x 10-4
13.
The two acid dissociation constants of carbonic acid (H2CO3) are 4.5 x 10-7 and 1 x 10-17. What is the concentration of CO32- in a
solution of 0.25 M H2CO3?
(A)
1 x 10-17
14.
Which of the following statements is false?
(A)
(B)
(C)
(D)
(E)
HBrO3 is a stronger acid than H2SeO3 even though the latter has 2 protons
HAt would be expected to be a strong acid
ClO- is a stronger base than ClO2HSe- is a stronger base than HS-.
If it existed, HFO4 would be expected to be a strong acid.
15.
Calculate the pH of a 0.35 M solution of CH3NH3Br, given that the Kb of CH3NH2 is 4.3 x 10-4.
(A)
5.54
16.
Given the following values of Ka, which is the weakest base of those listed:
Substance
HClO
HBrO
(A)
ClO2-
(B)
(E)
(B)
(B)
(B)
Ka
2.9 x 10-8
2.3 x 10-9
1.00 x 10-7
3.35 x 10-4
1.91
Substance
C6H5OH
HIO
(B)
6
7
BrO-
(C)
(C)
(C)
(C)
Ka
1.0 x 10-10
2.3 x 10-11
2.25
1.58 x 10-9
12.1
Substance
HClO2
(C)
(D)
C6H5O-
4
(D)
slightly more than 7
1.00 x 10-8
4.5 x 10-7
(E)
1.00 x 10-6
(E)
3.47
(D)
3.4
(E)
8.46
(D)
IO-
(E)
ClO-
Ka
.
1.12 x 10-2
17.
Which of the following solutions would be expected to have a pH of 7?
(A)
(B)
(C)
(D)
(E)
0.1 M HCl
0.25 M NaOH
0.30 M NH4Br
0.20 M NaF
0.10 M NaCl
18.
Identify the unknown particle X in each of the following:
I.
II.
III.
8
(A)
(D)
8
19.
The mass of carbon-14 is 14.003241 g/mol. Calculate the binding energy of a carbon-14 nucleus if the mass of a proton + electron is
1.00783 g/mol, the mass of a neutron = 1.00867 g/mol, the speed of light is 3.00 x 108 m/s and 1 J = 1 kg m2/s2.
(A)
1.05 x 1016 J/mol
20.
The naturally occurring radioactive decay series that begins with 235U stops with formation of the stable 207Pb. The decay proceeds
via a series of alpha and beta particle emissions. How many of each type of emission are involved in this series?
(A)
5 α, 8 β
B → β+ + X
14
C → X + 14N
238
U→α+X
8
Be, β+, 234Th
C, β−, 242Th
(B)
(E)
(B)
(B)
8
8
Be, β+, 242Th
Be, β−, 234Th
1.02 x 1013 J/mol
14 α, 4 β
(C)
(C)
(C)
9.57 x 1012 J/mol
7 α, 18 β
5
(D)
(D)
8
C, β−, 234Th
1.69 x 1011 J/mol
7 α, 4 β
(E)
(E)
34 J/mol
7 α, 8 β
CHEM 1332 SUMMER 2005
TEST 2 VERSION 2
NO CHEATING!
BUBBLE IN “1” IN THE P COLUMN TO GET YOUR GRADE POSTED!!!!! [the only way you’ll find out how you did!]
1.
Starting with 0.0350 M COCl2, calculate the equilibrium constant (Kc) for the reaction, COCl2(g) ∆ CO(g) + Cl2(g), if the
equilibrium concentration of CO is 0.0232 M.
(A)
1.54 x 10-2
2.
At 25.0 ºC, the reaction N2O4(g) ∆ 2 NO2(g) has an equilibrium constant, Kc, of 0.113. Calculate the concentration of NO2 at
equilibrium when 2.5 moles of N2O4 are placed into a 1.00 liter container.
(A)
(D)
0.532 moles/liter
0.266 moles/liter
3.
The reaction, CaSO3(s) ∆ CaO(s) + SO2(g), has a ∆Hº value of -150 kJ at 250 ºC. Which of the following would reduce the amount
of the poisonous gas, SO2, present at equilibrium.
(A)
(C)
(E)
Adding lots of CaO
Performing the reaction in a large volume container
Adding an appropriate catalyst
4.
Which of the following substances would NOT be considered to be amphiprotic in water?
(A)
H2O
5.
The Kw of water at 90 ºC is 1.0 x 10-12. At this temperature:
(A)
(B)
(C)
(D)
(E)
Water is acidic because the [H3O+] in pure water is 1 x 10-6 and so the pH is 6
0.1 M HCl will have a pH of less than 1.
pH + pOH = 12
The pH of 1 M NaOH would be 14 which is bigger than 12 so 1 M NaOH cannot exist at 90 ºC.
None of these are correct.
(B)
4.56 x 10-2
(B)
(E)
(B)
HCO3-
(C)
1.97
0.252 moles/liter
0.956 moles/liter
(C)
(B)
(D)
(C)
(D)
NH3
1
21.9
(E)
65.0
0.504 moles/liter
Removing CaSO3 as it is formed
Performing the reaction at high temperatures
(D)
H2PO4-
(E)
HSO3-
2
6.
Which of the following statements is FALSE?
(A)
(B)
(C)
(D)
(E)
A reaction is at equilibrium when the forward and reverse reactions occur at the same rate.
At equilibrium, the concentrations of all species present are constant.
Even though a reaction at equilibrium appears to have stopped, reactions are still taking place.
The equilibrium position depends upon the quantity of the starting materials.
The equilibrium position depends upon the temperature of the reaction.
7.
The gaseous reaction, 3 A + 6 B ∆ 3 C + 3 D has an equilibrium constant of 0.125. What is the value of the equilibrium constant for
the reaction, C + D ∆ A + 2 B?
(A)
0.00195
8.
The reaction, NH4SH(s) ∆ NH3(g) + H2S(g) has an equilibrium constant, Kc, of 7 at 313 K. If a mixture consisting of 1.5 moles of
NH4SH, 3.0 moles of NH3 and 3.0 moles of H2S in a 1 liter container is taken then:
(A)
(B)
(C)
(D)
(E)
The reaction is at equilibrium
The value of Q is 6 and the reaction goes to the right in order to reach equilibrium
The value of Q is 6 and the reaction goes to the left in order to reach equilibrium
The value of Q is 9 and the reaction goes to the left in order to reach equilibrium
The value of Q is 9 and the reaction goes to the right in order to reach equilibrium
9.
For which of the following equilibria does Kp = Kc?
(A)
(C)
(E)
C(s) + CO2(g) ∆ 2 CO(g)
2 H2(g) + O2(g) ∆ 2 H2O(g)
N2(g) + O2(g) ∆ 2 NO(g)
10.
At a given temperature, the equilibrium constant (Kc) for the reaction, 2 HCl(g) ∆ H2(g) + Cl2(g) is 12.5. When a given quantity of
HCl is introduced into a 1.00 liter container, the equilibrium concentration of HCl is 1.25 moles/liter. What is the equilibrium
concentration of H2(g)?
(A)
(D)
4.42 moles/liter
0.2 moles/liter
(B)
0.125
(C)
0.5
(B)
(D)
(B)
(E)
0.625 moles/liter
0.1 moles/liter
(D)
(E)
512
Cl2(g) ∆ 2 Cl(g)
CH4(g) + H2O(g) ∆ CO(g) + 3 H2(g)
(C)
3
2
0.3125 moles/liter
11.
Given the following values of Ka, which is the weakest base of those listed:
Substance
HClO
HBrO
Ka
2.9 x 10-8
2.3 x 10-9
Substance
C6H5OH
HIO
Ka
1.0 x 10-10
2.3 x 10-11
Ka
.
1.12 x 10-2
(A)
ClO2-
12.
Which of the following solutions would be expected to have a pH of 7?
(A)
(B)
(C)
(D)
(E)
0.1 M HCl
0.25 M NaOH
0.30 M NH4Br
0.20 M NaF
0.10 M NaCl
13.
Identify the unknown particle X in each of the following:
I.
II.
III.
8
(A)
(D)
8
14.
The mass of carbon-14 is 14.003241 g/mol. Calculate the binding energy of a carbon-14 nucleus if the mass of a proton + electron is
1.00783 g/mol, the mass of a neutron = 1.00867 g/mol, the speed of light is 3.00 x 108 m/s and 1 J = 1 kg m2/s2.
(A)
1.05 x 1016 J/mol
15.
The naturally occurring radioactive decay series that begins with 235U stops with formation of the stable 207Pb. The decay proceeds
via a series of alpha and beta particle emissions. How many of each type of emission are involved in this series?
(A)
5 α, 8 β
(B)
BrO-
Substance
HClO2
(C)
C6H5O-
(D)
IO-
(C)
8
(E)
ClO-
B → β+ + X
C → X + 14N
238
U→α+X
14
Be, β+, 234Th
8
C, β−, 242Th
(B)
(E)
(B)
(B)
Be, β+, 242Th
8
Be, β−, 234Th
8
1.02 x 1013 J/mol
14 α, 4 β
(C)
(C)
9.57 x 1012 J/mol
7 α, 18 β
4
(D)
(D)
C, β−, 234Th
1.69 x 1011 J/mol
7 α, 4 β
(E)
(E)
34 J/mol
7 α, 8 β
16.
Calculate the pH of 1.0 x 10-8 M HCl.
(A)
(D)
8
slightly less than 7
17.
An new weak acid, CH3CH2C(OH)2CH2C(OH)2CH2COOH is synthesized and a 0.1 M solution is found to have a pH of 3.50. What
is the Ka of the new acid?
(A)
3.17 x 10-4
18.
The two acid dissociation constants of carbonic acid (H2CO3) are 4.5 x 10-7 and 1 x 10-17. What is the concentration of CO32- in a
solution of 0.25 M H2CO3?
(A)
1 x 10-17
19.
Which of the following statements is false?
(A)
(B)
(C)
(D)
(E)
HBrO3 is a stronger acid than H2SeO3 even though the latter has 2 protons
HAt would be expected to be a strong acid
ClO- is a stronger base than ClO2HSe- is a stronger base than HS-.
If it existed, HFO4 would be expected to be a strong acid.
20.
Calculate the pH of a 0.35 M solution of CH3NH3Br, given that the Kb of CH3NH2 is 4.3 x 10-4.
(A)
5.54
(B)
(E)
(B)
(B)
(B)
1.00 x 10-7
3.35 x 10-4
1.91
6
7
(C)
(C)
(C)
(C)
2.25
1.58 x 10-9
12.1
5
(D)
(D)
(D)
slightly more than 7
1.00 x 10-8
4.5 x 10-7
3.4
(E)
1.00 x 10-6
(E)
3.47
(E)
8.46