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CHEMISTRY 102B/C
Hour Exam III
Fall 2014
Page 1
1. Consider the following reaction:
4 NO2(g) + O2(g) ⇌ 2 N2O5(g)
K = 6.2 × 106
If 4.0 moles of NO2 and 4.0 mol of O2 are placed in a 2.0 L container, what is the
equilibrium concentration of N2O5?
a) 1.4 × 102 M
b) 4.0 × 102 M
d) 7.0 × 103 M
e) 2.5 × 103 M
c) 8.0 × 102 M
Consider the following data for the next two questions:
Specific heat capacity of ice = 2.03 J/C  g
Specific heat capacity of water = 4.18 J/C  g
Specific heat capacity of steam = 2.02 J/C  g
Hfusion = 6.02 kJ/mol
Hvaporization = 40.7 kJ/mol
2.
Consider a 1.00 mole sample of ice at 30.0C, which is heated to steam at 140.0C.
Calculate q for the entire process.
a) 123 kJ
3.
b) 1070 kJ
d) 234 kJ
e) 56.8 kJ
A 500.0 g sample of an element at 195C is dropped into an ice-water mixture. 109.5 g
of ice melts and an ice-water mixture remains. Calculate the specific heat capacity of the
element.
a) 2.67 J/C  g
4.
c) 6.75 kJ
b) 0.375 J/C  g
c) 0.789 J/C  g
Which of the following mathematical relationships is false?
a) Esystem = Esurroundings
b) At constant pressure, q = E + PV.
c) Hsystem  Huniverse = Hsurroundings
d) At constant volume, E = q.
e) For a cyclic process, w = q.
d) 1.62 J/C  g
CHEMISTRY 102B/C
Hour Exam III
5.
Fall 2014
Page 2
Consider the following reaction:
2 NO2(g) ⇌ 2 NO(g) + O2(g)
K=?
4.0 moles of NO2 are placed in a 1.0 L container and are allowed to react to reach
equilibrium. At equilibrium the concentration of NO(g) is 1.0 M. Calculate the value of
the equilibrium constant, K, for this reaction.
a) 0.056
6.
c) 0.17
d) 25
e) 590
The Ksp value for BaF2 is 5.0 × 107. When 10.0 mL of 0.010 M NaF is mixed with 10.0
mL of 0.010 M Ba(NO3)2, will a precipitate form?
a)
b)
c)
d)
7.
b) 0.11
No, because Q = 1.0 × 106 and since it is greater than Ksp, no precipitate will form.
Yes, because Q = 1.0 × 106 and since it is greater than Ksp, a precipitate will form.
No, because Q = 1.3 × 107 and since it is less than Ksp, no precipitate will form.
Yes, because Q = 1.3 × 107 and since it is less than Ksp, a precipitate will form.
The reaction for the formation of the complex ion Cu(NH3)42+ is:
Cu2+(aq) + 4 NH3(aq)  Cu(NH3)42+(aq)
Which of the following is the correct expression for the equilibrium constant, K, for this
reaction?
2
2
8.
a) K 
[Cu(NH3 )4 ]
[Cu 2 ][NH3 ]
b) K 
[Cu(NH3 )4 ]4
[Cu 2 ][NH 3 ]4
d) K 
1
2
[Cu ][NH3 ]4
e) K 
[Cu(NH3 )4 ]
[Cu 2 ][NH 3 ]4
c) K 
1
[Cu ][NH3 ]
2
2
The heat capacity of a bomb calorimeter was determined by combusting 6.79 g of CH4
(energy of combustion of CH4 =  802 kJ/mol CH4); the temperature of the bomb
calorimeter increased by 10.8C. In a second experiment with the same bomb
calorimeter, combustion of a 12.6 g sample of ethyne, C2H2, produced a temperature
increase of 16.9C. Calculate the energy of combustion of C2H2 in kJ/mol.
a) 31.4 kJ/mol
b) 1.10 × 103 kJ/mol
d) 532 kJ/mol
e) 340. kJ/mol
c) 1.47 × 103 kJ/mol
CHEMISTRY 102B/C
Hour Exam III
9.
Fall 2014
Page 3
Consider the following reaction which has an enthalpy change of HT:
AX
H = HT
This reaction can be broken down into a series of steps as shown in the following
diagram:
Which of the following relationships must be true for this reaction?
a) HT  H1  H2  H3 = 0
b) H2  (H3 + H1) = HT
c) HT + H1 + H2 + H3 = 0
d) HT + H2 = H1 + H3
e) H3  (H1+ H2) = 0
10.
Consider the following reaction at some temperature:
Cl2(g) + F2(g)
⇌
2 ClF(g)
Kp = 16
If initially 3.00 atm of F2 and 3.00 atm of Cl2 are reacted in a rigid container, calculate
the equilibrium partial pressure of Cl2(g).
11.
a) 0.25 atm
b) 0.50 atm
d) 1.5 atm
e) 2.0 atm
c) 1.0 atm
A 50.0 mL sample of 0.200 M Ca(NO3)2 is mixed with 50.00 mL of 0.200 M NaF. When
the system has come to equilibrium, what are the equilibrium concentrations of Ca2+ and
F? Ksp for CaF2 = 4.0 × 1011.
a)
b)
c)
d)
e)
[Ca2+]e
5.0 × 102 M
1.0 × 101 M
2.2 × 104 M
1.0 × 101 M
5.0 × 102 M
[F]e
1.4 × 105 M
1.0 × 105 M
4.3 × 104 M
2.0 × 105 M
2.8 × 105 M
CHEMISTRY 102B/C
Hour Exam III
12.
Fall 2014
Page 4
Silver acetate (AgC2H3O2) is a sparingly soluble salt with Ksp = 1.9 × 103. Compare the
effects on the solubility of silver acetate by addition of HNO3 or by addition of NH3.
a) Addition of either HNO3 or NH3 would decrease the solubility of AgC2H3O2.
b) Addition of NH3 would increase the solubility of AgC2H3O2, but addition of HNO3
would decrease it.
c) Addition of NH3 would increase the solubility of AgC2H3O2, but addition of HNO3
would have virtually no effect.
d) Addition of either HNO3 or NH3 would increase the solubility of AgC2H3O2.
e) Addition of NH3 would decrease the solubility of AgC2H3O2, but addition of HNO3
would increase it.
13.
Using the bond energies below, estimate the enthalpy change in kJ for the reaction:
Bond Energy (kJ/mol)
CH
413
CO
358
C=O
745
OH
467
CC
347
HH
432
14.
a) H = 2654 kJ
b) H = 567 kJ
d) H = 0 kJ
e) H = 1258 kJ
c) H = 567
An equilibrium mixture for the reaction:
2 NH3(g) ⇌ N2(g) + 3 H2(g)
K=?
contains 9.0 mol N2, 6.0 mol H2, and 6.0 mol NH3, all in a 3.0 L container at a certain
temperature. Calculate the value of K for this reaction at this temperature.
a) 2.0
b) 4.0
d) 9.0
e) 12
c) 6.0
CHEMISTRY 102B/C
Hour Exam III
15.
16.
17.
Fall 2014
Page 5
Aluminum fluoride has a solubility of 6.66 × 102 mol/L. Calculate the Ksp value for
AlF3(s).
a) 4.44 × 103
b) 1.97 × 105
d) 5.31 × 104
e) 5.90 × 106
c) 5.90 × 105
Calculate the molar solubility of Ag2CO3(s) in an aqueous solution that is 0.50 M in
K2CO3. Ksp for Ag2CO3 = 8.2 × 1012
a) 2.0 × 106 mol/L
b) 2.6 × 104 mol/L
d) 2.8 × 106 mol/L
e) 3.4 × 103 mol/L
c) 1.3 × 104 mol/L
Given the following set of gas phase reactions:
H2 + Cl2  2 HCl
H2  2 H
Cl2  2 Cl
H = 184 kJ
H = 432 kJ
H = 240 kJ
calculate the bond energy of the HCl bond.
a) 248 kJ
18.
b) 428 kJ
c) 864 kJ
d) 92 kJ
e) 184 kJ
Determine E for a system which undergoes both of the following two processes:
I. 15 J of work is done on the system, while 30 J of heat is absorbed by it; then:
II. 20 J of heat is given off by the system, while 25 J of work is done by the system.
a) 30 J
19.
b) 30 J
c) 40 J
d) 45 J
e) 0
Consider the reaction:
NH4NO3(s)
⇌
N2O(g) + 2 H2O(g)
K = 4.85
200. g of NH4NO3(s) are placed in a reaction vessel containing H2O(g) at a concentration
of 2.0 M and N2O(g) at a concentration of 2.0 M. After equilibrium is reached, will the
mass of NH4NO3(s) increase, decrease or remain unchanged?
a) The mass of NH4NO3(s) will decrease (< 200. g).
b) The mass of NH4NO3(s) will increase (> 200. g).
c) The mass of NH4NO3(s) will remain unchanged (= 200. g).
CHEMISTRY 102B/C
Hour Exam III
20.
Fall 2014
Page 6
Consider the following endothermic reaction at equilibrium:
SiHCl3(g) + 3 H2O(g)
⇌ SiH(OH)3(s) + 3 HCl(g)
Which of the following would cause the reaction to shift toward reactants (shift left) to
reestablish equilibrium?
a)
b)
c)
d)
e)
21.
Adding H2O(g).
Increasing the temperature.
Adding Ar(g) (assume a constant volume container).
Increasing the volume of the reaction container.
Adding SiH(OH)3(s).
How many of the following five quantities is/are state functions?
I. work
IV. pressure
a) none
22
II. enthalpy
V. temperature
b) 1
c) 2
III. highway distance from Peoria to Champaign
d) 3
e) 5 (All are state functions.)
Consider the reaction:
Ca3P2(s) + 6 H2O(l)  3 Ca(OH)2(s) + 2 PH3(g)
H = 721.70 kJ
If this reaction were carried out at 298 K in a beaker open to a constant-pressure
atmosphere, which of the following would be false?
23.
a) E = 716.74 kJ
b) w = 4.96 kJ
d) The reaction is exothermic.
e) Heat is released.
c) qp = 721.70 kJ
The following reaction was studied in a coffee cup calorimeter:
2 HCl(aq) + Ba(OH)2(aq)  BaCl2(aq) + 2 H2O(l)
H = 118 kJ
In the coffee cup calorimeter, 100.00 mL of 0.500 M HCl was mixed with 300.0 mL of
0.500 M Ba(OH)2. Assuming a solution density of 1.00 g/mL, a solution heat capacity of
4.18 J/C  g, an initial solution temperature of 25.00C, and no heat loss to the coffee
cups, calculate the final temperature of the reaction mixture.
a) 23.24C
b) 25.92C
c) 2.89C
d) 27.89C
e) 26.76C
CHEMISTRY 102B/C
Hour Exam III
24.
When ethene gas, C2H4, is combusted at 298 K, CO2(g) and H2O(l) are produced. The
enthalpy of combustion of ethene at 298 K is 1411.1 kJ/mol ethene. Given the
following standard enthalpies of formation, calculate the standard enthalpy of formation
for ethene.
Hf
393.5 kJ/mol
285.9 kJ/mol
CO2(g)
H2O(l)
25.
26.
Fall 2014
Page 7
a) 52.3 kJ/mol
b) 731.7 kJ/mol
d) 126.2 kJ/mol
e) 296.0 kJ/mol
c) 2769.9 kJ/mol
The solubility of La(IO3)3 in a 0.10 M KIO3 solution is 1.0 × 107 mol/L. Calculate the
Ksp value for La(IO3)3.
a) 1.0 × 108
b) 2.7 × 109
d) 2.7 × 1027
e) 6.2 × 108
c) 1.0 × 1010
Consider the following five reactions:
I. P4(s) + 6 Cl2(g)  4 PCl3(g)
II. P4(s) + 5 O2(g)  P4O10(g)
III. PCl3(g) + ½ O2(g)  Cl3PO(l)
IV. PCl3(g) + Cl2(g)  PCl5(g)
V. P4O10(s) + 6 PCl5(g)  10 Cl3PO(l)
For which reaction should bond energies give the best estimation for Hreaction?
a) I
27.
b) II
c) III
d) IV
e) V
Which of the following compounds has the smallest molar solubility (mol/L) in water?
a) Al(OH)3
Ksp = 2 × 1032
b) CdS
Ksp = 1 × 1028
c) PbSO4
Ksp = 1 × 108
d) Sn(OH)2
Ksp = 3 × 1027
e) MgC2O4
Ksp = 9 × 105
CHEMISTRY 102B/C
Hour Exam III
28.
Fall 2014
Page 8
Consider two salts, PbX2 and PbY2, both of which have very similar Ksp values.
Assuming HX is a strong acid and HY is a weak acid, which salt is more soluble in acidic
solution?
a) PbX2
b) PbY2
c) They should be equally soluble in acidic solution.
29.
The standard enthalpy of formation for liquid water is 286 kJ/mol. For which of the
following reactions does Hreaction = 286 kJ?
a) H2O(l)  2 H(g) + O(g)
b) 2 H(g) + O(g)  H2O(l)
c) H2(g) + ½ O2(g)  H2O(l)
d) H2O(l)  H2(g) + ½ O2(g)
e) H2O(g)  H2O(l)
30.
Consider when 1.0 mole of A(g) and 1.0 mole of B(g) are added to a 2.0 L container and
the following balanced reaction occurs:
A(g) + 2 B(g) ⇌ 2 C(g) + 3 D(g)
Which of the following statements must be true regarding this reaction once equilibrium
has been reached?
a) The value of the equilibrium constant for this reaction must be greater than 1 (K > 1).
b) The value of the equilibrium constant for this reaction must be greater than 1 (K < 1).
c) At equilibrium, the rate of the reverse reaction must be greater than the rate of the
forward reaction.
d) At equilibrium, the concentration of B(g) must be equal to the concentration of C(g)
([B]e = [C]e).
e) At equilibrium, the concentration of B(g) must be smaller than the concentration of
A(g) ([B]e < [A]e).
31.
My chemistry 102 exam should be graded with the answer sheet associated with:
a) Form A
b) Form B
c) Form C
d) Form D
e) Form E