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56. The heat of combustion of benzene, C6H6, is –41.74 kJ/g. Combustion of 2.82 g of benzene
causes a temperature rise of 3.29°C in a certain bomb calorimeter. What is the heat capacity
of this bomb calorimeter?
A)
387 kJ/°C
B)
35.8 kJ/°C
C)
0.222 kJ/°C
D)
5.96 kJ/°C
E)
118 kJ/°C
57. The specific heat capacities of metals are relatively low.
58. The change in enthalpy can always be thought of as equal to energy flow as heat.
59. Which of the following statements is/are true?
I. q (heat) is a state function because H is a state function and q = H.
II. When 50.0 g of aluminum at 20.0°C is placed in 50.0 mL of water at 30.0°C, the
H2O will undergo a smaller temperature change than the aluminum. (The density of
H2O = 1.0 g/mL, specific heat capacity of H2O = 4.18 J/g°C, specific heat capacity
of aluminum = 0.89 J/g°C)
III. When a gas is compressed, the work is negative since the surroundings are
doing work on the system and energy flows out of the system.
IV. For the reaction (at constant pressure) 2N2(g) + 5O2(g) → 2N2O5(g), the change
in enthalpy is the same whether the reaction takes place in one step or in a series of
steps.
A)
I, II, IV
B)
II, III
C)
II, III, IV
D)
II, IV
E)
All of the above statements are true.
60. Consider the following processes:
2A → (1/2)B + C
H1 = 5 kJ/mol
(3/2)B + 4C → 2A + C + 3D
H2 = –15 kJ/mol
E + 4A → C
H3 = 10 kJ/mol
Calculate H for: C → E + 3D
A)
0 kJ/mol
B)
10 kJ/mol
C)
–10 kJ/mol
D)
–20 kJ/mol
E)
20 kJ/mol
61. Consider the following processes:
H (kJ/mol)
3B → 2C + D
–125.
(1/2)A → B
150
E + A → D
350
Calculate H for: B → E + 2C
A)
325 kJ/mol
B)
525 kJ/mol
C)
–175 kJ/mol
D)
–325 kJ/mol
E)
none of these
62. Consider the following numbered processes:
1.
A → 2B
2.
B → C + D
3.
E → 2D
H for the process A → 2C + E is
A)
H1 + H2 + H3
B)
H1 + H2
C)
H1 + H2 – H3
D)
H1 + 2H2 – H3
E)
H1 + 2H2 + H3
63. At 25°C, the following heats of reaction are known:
H (kJ/mol)
2ClF + O2 → Cl2O + F2O
167.4
2ClF3 + 2O2 → Cl2O + 3F2O
341.4
2F2 + O2 → 2F2O
–43.4
At the same temperature, calculate H for the reaction: ClF + F2 → ClF3
A)
–217.5 kJ/mol
B)
–130.2 kJ/mol
C)
+217.5 kJ/mol
D)
–108.7 kJ/mol
E)
none of these
64. Calculate H° for the reaction C4H4(g) + 2H2(g) → C4H8(g), using the following data:
H°combustion for C4H4(g) = –2341 kJ/mol
H°combustion for H2(g) = –286 kJ/mol
H°combustion for C4H8(g) = –2755 kJ/mol
A)
–128 kJ
B)
–158 kJ
C)
128 kJ
D)
158 kJ
E)
none of these
65. Given the heats of the following reactions:
H°(kJ)
I.
P4(s) + 6Cl2(g) → 4PCl3(g)
–1225.6
II.
P4(s) + 5O2(g) → P4O10(s)
–2967.3
III.
PCl3(g) + Cl2(g) → PCl5(g)
–84.2
IV.
PCl3(g) + O2(g) → Cl3PO(g)
–285.7
Calculate the value of H° for the reaction below:
P4O10(s) + 6PCl5(g) → 10Cl3PO(g)
A)
–110.5 kJ
B)
–610.1 kJ
C)
–2682.2 kJ
D)
–7555.0 kJ
E)
None of these is within 5% of the correct answer.
66. Using the following thermochemical data:
2Cr(s) + 6HF(g) → 2CrF3(s) + 3H2(g)
H° = –691.4 kJ/mol
2Cr(s) + 6HCl(g) → 2CrCl3(s) + 3H2(g)
H° = –559.2 kJ/mol
calculate H° for the following reaction:
CrF3(s) + 3HCl(g) → CrCl3(s) + 3HF(g)
A)
–1250.6 kJ/mol
B)
132.2 kJ/mol
C)
66.1 kJ/mol
D)
264.4 kJ/mol
E)
–625.3 kJ/mol
67. Using the following thermochemical data, calculate Hf° of Tm2O3(s).
2TmCl3(s) + 3H2O(l) → Tm2O3(s) + 6HCl(g)
H° = 388.1 kJ/mol
2Tm(s) + 3Cl2(g) → 2TmCl3(s)
H° = –1973.2 kJ/mol
4HCl(g) + O2(g) → 2Cl2(g) + 2H2O(l)
H° = –202.4 kJ/mol
A)
–1888.7 kJ/mol
B)
–1787.5 kJ/mol
C)
2563.7 kJ/mol
D)
–2158.9 kJ/mol
E)
1382.7 kJ/mol
68. The heat of formation of Fe2O3(s) is –826.0 kJ/mol. Calculate the heat of the reaction
when a 53.99-g sample of iron is reacted.
A)
–199.6 kJ
B)
–399.2 kJ
C)
–798.5 kJ
D)
–1597 kJ
E)
–2.230 104 kJ
69. Which of the following does not have a standard enthalpy of formation equal to zero at 25°C
and 1.0 atm?
A)
F2(g)
B)
Al(s)
C)
H2O(l)
D)
H2(g)
E)
They all have a standard enthalpy equal to zero.
70. Given the following two reactions at 298 K and 1 atm, which of the statements is true?
1.
N2(g) + O2(g) → 2NO(g)
H1
2.
NO(g) + O2(g) → NO2(g)
H2
A)
Hf° for NO2(g) = H2
B)
Hf° for NO(g) = H1
C)
Hf° = H2
D)
Hf° for NO2(g) = H2 + H1
E)
none of these
71. Given:
Cu2O(s) + O2(g) → 2CuO(s)
H° = –144 kJ
Cu2O(s) → Cu(s) + CuO(s)
H° = +11 kJ
Calculate the standard enthalpy of formation of CuO(s).
A)
–166 kJ
B)
–299 kJ
C)
+299 kJ
D)
+155 kJ
E)
–155 kJ
72. Using the following data, calculate the standard heat of formation of the compound ICl in
kJ/mol:
H° (kJ/mol)
Cl2(g) → 2Cl(g)
242.3
I2(g) → 2I(g)
151.0
ICl(g) → I(g) + Cl(g)
211.3
I2(s) → I2(g)
62.8
A)
–211 kJ/mol
B)
–14.6 kJ/mol
C)
16.8 kJ/mol
D)
245 kJ/mol
E)
439 kJ/mol
73. The heat combustion of acetylene, C2H2(g), at 25°C is –1299 kJ/mol. At this temperature,
Hf° values for CO2(g) and H2O(l) are –393 and –286 kJ/mol, respectively. Calculate Hf°
for acetylene.
A)
2376 kJ/mol
B)
625 kJ/mol
C)
227 kJ/mol
D)
–625 kJ/mol
E)
–227 kJ/mol
74. Choose the correct equation for the standard enthalpy of formation of CO(g), where Hf°
for CO = –110.5 kJ/mol (gr indicates graphite).
A)
2C(gr) + O2(g) → 2CO(g), H° = –110.5 kJ
B)
C(gr) + O(g) → CO(g), H° = –110.5 kJ
C)
C(gr) + O2(g) → CO(g), H° = –110.5 kJ
D)
C(gr) + CO2(g) → 2CO(g), H° = –110.5 kJ
E)
CO(g) → C(gr) + O(g), H° = –110.5 kJ
75. For the reaction:
AgI(s) + Br2(g) → AgBr(s) + I2(s), H° = –54.0 kJ
Hf° for AgBr(s) = –100.4 kJ/mol
Hf° for Br2(g) = +30.9 kJ/mol
The value of Hf° for AgI(s) is:
A)
–123.5 kJ/mol
B)
+77.3 kJ/mol
C)
+61.8 kJ/mol
D)
–77.3 kJ/mol
E)
–61.8 kJ/mol
76. Using the information below, calculate Hf° for PbO(s)
PbO(s) + CO(g) → Pb(s) + CO2(g) H° = –131.4 kJ
Hf° for CO2(g) = –393.5 kJ/mol
Hf° for CO(g) = –110.5 kJ/mol
A)
–151.6 kJ/mol
B)
–283.0 kJ/mol
C)
+283.0 kJ/mol
D)
–372.6 kJ/mol
E)
+252.1 kJ/mol
77. For which of the following reaction(s) is the enthalpy change for the reaction not equal to
Hf° of the product?
I.
2H(g) → H2(g)
II.
H2(g) + O2(g) → H2O2(l)
III.
H2O(l) + O(g) → H2O2(l)
A)
I
B)
II
C)
III
D)
I and III
E)
II and III
78. Consider the reaction:
2ClF3(g) + 2NH3(g) → N2(g) + 6HF(g) + Cl2(g)
When calculating the H°rxn, why is the Hf° for N2 not important?
A)
Because nitrogen is in its standard elemental state and no energy is needed for this
product to exist.
B)
Because any element or compound in the gaseous state requires a negligible
amount of energy to exist.
C)
Because the products are not included when calculating H°rxn.
D)
Because nitrogen is in its elemental state and does not contribute to the reaction
itself.
E)
Two of the above statements explain why N2 is not important when calculating
H°rxn.
79. The following statements concerning petroleum are all true except:
A)
It is a thick, dark liquid composed mostly of hydrocarbons.
B)
It must be separated into fractions (by boiling) in order to be used efficiently.
C)
Some of the commercial uses of petroleum fractions include gasoline and
kerosene.
D)
It was probably formed from the remains of ancient marine organisms.
E)
All of its hydrocarbon chains contain the same number of carbon atoms.
80. This fossil fuel was formed from the remains of plants that were buried and exposed to high
pressure and heat over time.
A)
coal
B)
natural gas
C)
diesel fuel
D)
propane
E)
gasoline
81. The coal with the highest energy available per unit burned is
A)
Lignite.
B)
Subbituminous.
C)
Bituminous.
D)
Anthracite.
E)
They are equal in energy value.
82. All of the following statements about the greenhouse effect are true except:
A)
It occurs only on earth.
B)
The molecules H2O and CO2 play an important role in retaining the atmosphere's
heat.
C)
Low humidity allows efficient radiation of heat back into space.
D)
The carbon dioxide content of the atmosphere is quite stable.
E)
A and D
83. Which of the following is both a greenhouse gas and a fuel?
A)
carbon dioxide
B)
coal
C)
freon
D)
methane
E)
nitrogen
84. One of the main advantages of hydrogen as a fuel is that:
A)
The only product of hydrogen combustion is water.
B)
It exists as a free gas.
C)
It can be economically supplied by the world's oceans.
D)
Plants can economically produce the hydrogen needed.
E)
It contains a large amount of energy per unit volume of hydrogen gas.
85. Which of the following is not being considered as an energy source for the future?
A)
ethanol
B)
methanol
C)
seed oil
D)
shale oil
E)
carbon dioxide
86. The combustion of hydrogen gas releases 286 kJ per mol of hydrogen. If 13.0 L of hydrogen
at STP was burned to produce electricity, how long would it power a 100-watt (W) light
bulb? Assume no energy is lost to the surroundings. (1 W = 1 J/s)
A)
27.7 min
B)
1.92 days
C)
1.66 hr
D)
10.3 hr
E)
4.61 hr
87. The __________ of a system is the sum of the kinetic and potential energies of all the
particles in the system.
88. __________ involves the transfer of energy between two objects due to a temperature
difference.
89. Consider the reaction:
N2(g) + 3H2(g) → 2NH3(g)
Assuming this reaction takes place in an elastic balloon with an atmospheric pressure of 1.0
atm, and that you have a stoichiometric mixture of nitrogen and hydrogen, draw a
microscopic diagram before and after the reaction occurs. See the example below to assist
you.
ABC2(g) → AB(g) + C2(g) (could be drawn as)
In addition, explain whether w (the work done) is positive, negative, or zero.
90. Consider the following reaction:
2Al(s) + 3Cl2(g) → 2AlCl3(s); H = –1390.81 kJ
a) Is the reaction exothermic or endothermic?
b) How much heat is produced/required when 10.0 g AlCl3 forms.
c) How many grams of Al are required to absorb/evolve 1.00 kJ of energy?
91. How much energy (absolute value) is involved in the reaction 2NO2 → N2O4?
92. Is the reaction endothermic or exothermic?
93. Consider the following data:
H° (kJ)
Ca(s) + 2C(graphite) → CaC2(s)
–62.8
Ca(s) + O2(g) → CaO(s)
–635.5
CaO(s) + H2O(l) → Ca(OH)2(aq)
–653.1
C2H2(g) + O2(g) → 2CO2(g) + H2O(l)
–1300
C(graphite) + O2(g) → CO2(g)
–393.51
Use Hess’ law to find the change in enthalpy at 25°C for the following equation:
CaC2(s) + 2H2O(l) → Ca(OH)2(aq) + C2H2(g)
94. Consider the following standard heats of formation:
P4O10(s) = –3110 kJ/mol
H2O(l) = –286 kJ/mol
H3PO4(s) = –1279 kJ/mol
Calculate the change in enthalpy for the following process:
P4O10(s) + 6H2O(l) → 4H3PO4(s)
95. Acetylene (C2H2) and butane (C4H10) are gaseous fuels. Determine the ratio of energy
available from the combustion of a given volume of acetylene to butane at the same
temperature and pressure using the following data:
The change in enthalpy of combustion for C2H2(g) = –49.9 kJ/g.
The change in enthalpy of combustion for C4H10(g) = –49.5 kJ/g.
