Chemistry: A Molecular Approach, 3e (Tro)
Chapter 6 Thermochemistry
Multiple Choice Questions
1) Energy that is associated with the position or composition of an object is called
A) kinetic energy
B) thermal energy
C) potential energy
D) chemical energy
2) Energy that is associated with the motion of an object is called
A) kinetic energy
B) thermal energy
C) potential energy
D) chemical energy
3) Energy that is associated with the temperature of an object is called
A) kinetic energy
B) thermal energy
C) potential energy
D) chemical energy
4) Energy that is associated with the relative positions of electrons and nuclei in atoms and molecules is
called
A) kinetic energy
B) thermal energy
C) potential energy
D) chemical energy
5) The law of ________ states that energy that can be neither created or destroyed.
A) kinetic energy
B) the consecration of energy
C) potential energy
D) the conservation of energy
E) thermochemistry
6) Which of the following signs on q and w represent a system that is doing work on the surroundings,
as well as losing heat to the surroundings?
A) q = -, w = –
B) q = +, w = +
C) q = -, w = +
D) q = +, w = –
E) None of these represent the system referenced above.
7) Which of the following signs on q and w represent a system that is doing work on the surroundings,
as well as gaining heat from the surroundings?
A) q = +, w = –
B) q = -, w = +
C) q = +, w = +
D) q = -, w = –
E) None of these represent the system referenced above.
8) For ΔEsys to always be -, what must be true?
A) q = w
B) +q > -w
C) +w > -q
D) -w > +q
9) Which of the following (with specific heat capacity provided) would show the smallest temperature
change upon gaining 200.0 J of heat?
A) 50.0 g Al, CAl = 0.903 J/g°C
B) 50.0 g Cu, CCu = 0.385 J/g°C
C) 25.0 g granite, Cgranite = 0.79 J/g°C
D) 25.0 g Au, CAu = 0.128 J/g°C
E) 25.0 g Ag, CAg = 0.235 J/g°C
10) Determine the specific heat capacity of an alloy that requires 59.3 kJ to raise the temperature of
150.0 g alloy from 298 K to 398 K.
A) 4.38 J/g°C
B) 2.29 J/g°C
C) 3.95 J/g°C
D) 2.53 J/g°C
E) 1.87 J/g°C
11) A sample of copper absorbs 43.6 kJ of heat, resulting in a temperature rise of 75.0°C, determine the
mass (in kg) of the copper sample if the specific heat capacity of copper is 0.385 J/g°C.
A) 1.51 kg
B) 6.62 kg
C) 1.26 kg
D) 7.94 kg
E) 3.64 kg
12) Determine the final temperature of a gold nugget (mass = 376 g) that starts at 398 K and loses 4.85
kJ of heat to a snowbank when it is lost. The specific heat capacity of gold is 0.128 J/g°C.
A) 133 K
B) 398 K
C) 187 K
D) 297 K
E) 377 K
13) Calculate the change in internal energy (ΔE) for a system that is giving off 25.0 kJ of heat and is
changing from 12.00 L to 6.00 L in volume at 1.50 atm pressure. (Remember that 101.3 J = 1 L∙atm)
A) +25.9 kJ
B) -16.0 kJ
C) -25.9 kJ
D) -24.1 kJ
E) 937 kJ
14) Calculate the change in internal energy (ΔE) for a system that is giving off 25.0 kJ of heat and is
changing from 18.00 L to 15.00 L in volume at 1.50 atm pressure. (Remember that 101.3 J = 1 L∙atm)
A) +25.5 kJ
B) -16.0 kJ
C) -25.5 kJ
D) -24.5 kJ
E) 456 kJ
15) A 6.55 g sample of aniline (C6H5NH2, molar mass = 93.13 g/mol) was combusted in a bomb
calorimeter. If the temperature rose by 32.9°C, use the information below to determine the heat capacity
of the calorimeter.
4 C6H5NH2(l) + 35 O2(g) → 24 CO2(g) + 14 H2O(g) + 4 NO2(g)
ΔH°rxn = -1.28 x 104 kJ
A) 97.3 kJ/°C
B) 38.9 kJ/°C
C) 5.94 kJ/°C
D) 6.84 kJ/°C
E) 12.8 kJ/°C
16) A 21.8 g sample of ethanol (C2H5OH) is burned in a bomb calorimeter, according to the following
reaction. If the temperature rises from 25.0 to 62.3°C, determine the heat capacity of the calorimeter.
The molar mass of ethanol is 46.07 g/mol.
C2H5OH(l) + 3 O2(g) → 2 CO2(g) + 3 H2O(g) ΔH°rxn = -1235 kJ
A) 4.99 kJ/°C
B) 5.65 kJ/°C
C) 63.7 kJ/°C
D) 33.1 kJ/°C
E) 15.7 kJ/°C
17) A 4.98 g sample of aniline (C6H5NH2, molar mass = 93.13 g/mol) was combusted in a bomb
calorimeter with a heat capacity of 4.25 kJ/°C. If the temperature rose from 29.5°C to 69.8°C,
determine the value of ΔH°comb for aniline.
A) +7.81 × 103 kJ/mol
B) -3.20 × 103 kJ/mol
C) +1.71 × 103 kJ/mol
D) -1.71 × 103 kJ/mol
E) -7.81 × 103 kJ/mol
18) The temperature rises from 25.00°C to 29.00°C in a bomb calorimeter when 3.50 g of sucrose
undergoes combustion in a bomb calorimeter. Calculate ΔErxn for the combustion of sucrose in kJ/mol
sucrose. The heat capacity of the calorimeter is 4.90 kJ/°C. The molar mass of sugar is 342.3 g/mol.
A) – 1.92 x 103 kJ/mole
B) 1.92 x 103 kJ/mole
C) – 1.23 x 103 kJ/mole
D) 2.35 x 104 kJ/mole
19) A 12.8 g sample of ethanol (C2H5OH) is burned in a bomb calorimeter with a heat capacity of
5.65 kJ/°C. Using the information below, determine the final temperature of the calorimeter if the initial
temperature is 25.0°C. The molar mass of ethanol is 46.07 g/mol.
C2H5OH(l) + 3 O2(g) → 2 CO2(g) + 3 H2O(g) ΔH°rxn = -1235 kJ
A) 53.4°C
B) 28.1°C
C) 111°C
D) 85.7°C
E) 74.2°C
20) A 35.6 g sample of ethanol (C2H5OH) is burned in a bomb calorimeter, according to the following
reaction. If the temperature rose from 35.0 to 76.0°C and the heat capacity of the calorimeter is
23.3 kJ/°C, what is the value of DH°rxn? The molar mass of ethanol is 46.07 g/mol.
C2H5OH(l) + 3 O2(g) → 2 CO2(g) + 3 H2O(g) ΔH°rxn = ?
A) -1.24 × 103 kJ/mol
B) +1.24 × 103 kJ/mol
C) -8.09 × 103 kJ/mol
D) -9.55 × 103 kJ/mol
E) +9.55 × 103 kJ/mol
21) A 6.55 g sample of aniline (C6H5NH2, molar mass = 93.13 g/mol) was combusted in a bomb
calorimeter with a heat capacity of 14.25 kJ/°C. If the initial temperature was 32.9°C, use the
information below to determine the value of the final temperature of the calorimeter.
4 C6H5NH2(l) + 35 O2(g) → 24 CO2(g) + 14 H2O(g) + 4 NO2(g)
ΔH°rxn = -1.28 x 104 kJ
A) 257°C
B) 46.6°C
C) 48.7°C
D) 41.9°C
E) 931°C
22) Which statement is FALSE?
A) An exothermic reaction gives heat off heat to the surroundings.
B) Enthalpy is the sum of a system’s internal energy and the product of pressure and volume.
C) ΔErxn is a measure of heat.
D) ΔHrxn is the heat of reaction.
E) Endothermic has a positive ΔH.
23) Given w = 0, an endothermic reaction has the following.
A) +ΔH and –ΔE
B) – ΔH and +ΔE
C) + ΔH and +ΔE
D) – ΔH and –ΔE
24) How much energy is required to decompose 765 g of PCl3, according to the reaction below? The
molar mass of PCl3 is 137.32 g/mol and may be useful.
4 PCl3(g) → P4(s) + 6 Cl2(g) ΔH°rxn = +1207 kJ
A) 2.31 × 103 kJ
B) 4.33 × 103 kJ
C) 6.72 × 103 kJ
D) 1.68 × 103 kJ
E) 5.95 × 103 kJ
25) How much energy is required to decompose 612 g of PCl3, according to the reaction below? The
molar mass of PCl3 is 137.32 g/mol and may be useful.
4 PCl3(g) → P4(s) + 6 Cl2(g) ΔH°rxn = +1207 kJ
A) 1.85 × 103 kJ
B) 3.46 × 103 kJ
C) 5.38 × 103 kJ
D) 1.34 × 103 kJ
E) 4.76 × 103 kJ
26) How much energy is evolved during the formation of 98.7 g of Fe, according to the reaction below?
Fe2O3(s) + 2 Al(s) → Al2O3(s) + 2 Fe(s) ΔH°rxn = -852 kJ
A) 753 kJ
B) 1.51 x 103 kJ
C) 4.20 x 103 kJ
D) 482 kJ
E) 241 kJ
27) How much energy is evolved during the formation of 197 g of Fe, according to the reaction below?
Fe2O3(s) + 2 Al(s) → Al2O3(s) + 2 Fe(s) ΔH°rxn = -852 kJ
A) 1.52 x 103 kJ
B) 3.02 x 103 kJ
C) 8.40 x 103 kJ
D) 964 kJ
E) 482 kJ
28) Using the following thermochemical equation, determine the amount of heat produced per kg of
CO2 formed during the combustion of benzene (C6H6).
2 C6H6(l) + 15 O2(g) → 12 CO2(g) + 6 H2O(g) ΔH°rxn = -6278 kJ
A) 1.43 × 105 kJ/kg CO2
B) 2.30 × 104 kJ/kg CO2
C) 4.34 × 104 kJ/kg CO2
D) 1.19 × 104 kJ/kg CO2
E) 8.40 × 105 kJ/kg CO2
29) Using the following equation for the combustion of octane, calculate the amount of moles of carbon
dioxide formed from 100.0 g of octane. The molar mass of octane is 114.33 g/mole. The molar mass of
carbon dioxide is 44.0095 g/mole.
2 C8H18 + 25 O2 → 16 CO2 + 18 H2O ΔH°rxn = -11018 kJ
A) 18.18 moles
B) 6.997 moles
C) 14.00 moles
D) 8.000 moles
E) 10.93 moles
30) Using the following equation for the combustion of octane, calculate the amount of moles of oxygen
that reacts with 100.0 g of octane. The molar mass of octane is 114.33 g/mole. The molar mass of
carbon dioxide is 44.0095 g/mole.
2 C8H18 + 25 O2 → 16 CO2 + 18 H2O ΔH°rxn = -11018 kJ
A) 18.18 moles
B) 6.997 moles
C) 14.00 moles
D) 8.000 moles
E) 10.93 moles
31) According to the following reaction, how much energy is evolved during the reaction of 32.5 g
B2H6 and 72.5 g Cl2? The molar mass of B2H6 is 27.67 g/mol.
B2H6(g) + 6 Cl2(g) → 2 BCl3(g) + 6 HCl(g) ΔH°rxn = -1396 kJ
A) 1640 kJ
B) 238 kJ
C) 1430 kJ
D) 3070 kJ
E) 429 kJ
32) According to the following reaction, how much energy is evolved during the reaction of 2.50 L
B2H6 and 5.65 L Cl2 (Both gases are initially at STP)? The molar mass of B2H6 is 27.67 g/mol.
B2H6(g) + 6 Cl2(g) → 2 BCl3(g) + 6 HCl(g) ΔH°rxn = -1396 kJ
A) 58.7 kJ
B) 156 kJ
C) 215 kJ
D) 352 kJ
E) 508 kJ
33) According to the following thermochemical equation, what mass of HF (in g) must react in order to
produce 345 kJ of energy? Assume excess SiO2.
SiO2(s) + 4 HF(g) → SiF4(g) + 2 H2O(l) ΔH°rxn = -184 kJ
A) 42.7 g
B) 37.5 g
C) 150. g
D) 107 g
E) 173 g
34) Using the following equation for the combustion of octane, calculate the amount of grams of carbon
dioxide formed from 100.0 g of octane. The molar mass of octane is 114.33 g/mole. The molar mass of
carbon dioxide is 44.0095 g/mole.
2 C8H18 + 25 O2 → 16 CO2 + 18 H2O ΔH°rxn = -11018 kJ
A) 800.1 g
B) 307.9 g
C) 260.1 g
D) 792.3 g
35) What volume of benzene (C6H6, d= 0.88 g/mL, molar mass = 78.11 g/mol) is required to produce
1.5 x 103 kJ of heat according to the following reaction?
2 C6H6(l) + 15 O2(g) → 12 CO2(g) + 6 H2O(g) ΔH°rxn = -6278 kJ
A) 75 mL
B) 37 mL
C) 21 mL
D) 19 mL
E) 42 mL
36) Which of the following statements is TRUE?
A) State functions do not depend on the path taken to arrive at a particular state.
B) DErxn can be determined using constant volume calorimetry.
C) Energy is neither created nor destroyed, excluding nuclear reactions.
D) ΔHrxn can be determined using constant pressure calorimetry.
E) All of the above are true.
37) Two aqueous solutions are both at room temperature and are then mixed in a coffee cup calorimeter.
The reaction causes the temperature of the resulting solution to fall below room temperature. Which of
the following statements is TRUE?
A) The products have a lower potential energy than the reactants.
B) This type of experiment will provide data to calculate ΔErxn.
C) The reaction is exothermic.
D) Energy is leaving the system during reaction.
E) None of the above statements are true.
38) A piece of iron (mass = 25.0 g) at 398 K is placed in a styrofoam coffee cup containing 25.0 mL of
water at 298 K. Assuming that no heat is lost to the cup or the surroundings, what will the final
temperature of the water be? The specific heat capacity of iron = 0.449 J/g°C and water = 4.18 J/g°C.
A) 348 K
B) 308 K
C) 287 K
D) 325 K
E) 388 K
39) A student is preparing to perform a series of calorimetry experiments. She first wishes to determine
the calorimeter constant (Ccal) for her coffee cup calorimeter. She pours a 50.0 mL sample of water at
345 K into the calorimeter containing a 50.0 mL sample of water at 298 K. She carefully records the
final temperature of the water as 317 K. What is the value of Ccal for the calorimeter?
A) 19 J/K
B) 28 J/K
C) 99 J/K
D) 21 J/K
E) 76 J/K
40) A 100.0 mL sample of 0.300 M NaOH is mixed with a 100.0 mL sample of 0.300 M HNO3 in a
coffee cup calorimeter. If both solutions were initially at 35.00°C and the temperature of the resulting
solution was recorded as 37.00°C, determine the ΔH°rxn (in units of kJ/mol NaOH) for the
neutralization reaction between aqueous NaOH and HCl. Assume 1) that no heat is lost to the
calorimeter or the surroundings, and 2) that the density and the heat capacity of the resulting solution are
the same as water.
A) -55.7 kJ/mol NaOH
B) -169 kJ/mol NaOH
C) -16.7 kJ/mol NaOH
D) -27.9 kJ/mol NaOH
E) – 34.4 kJ/mol NaOH
41) Two solutions, initially at 24.60°C, are mixed in a coffee cup calorimeter (Ccal = 15.5 J/°C). When
a 100.0 mL volume of 0.100 M AgNO3 solution is mixed with a 100.0 mL sample of 0.200 M NaCl
solution, the temperature in the calorimeter rises to 25.30°C. Determine the DH°rxn for the reaction as
written below. Assume that the density and heat capacity of the solutions is the same as that of water.
NaCl(aq) + AgNO3(aq) → AgCl(s) + NaNO3(aq) DH°rxn = ?
A) -35 kJ
B) -69 kJ
C) -250 kJ
D) -16 kJ
E) -140 kJ
42) Two solutions, initially at 24.69°C, are mixed in a coffee cup calorimeter (Ccal = 105.5 J/°C).
When a 200.0 mL volume of 0.100 M AgNO3 solution is mixed with a 100.0 mL sample of 0.100 M
NaCl solution, the temperature in the calorimeter rises to 25.16°C. Determine the DH°rxn, in units of
kJ/mol AgCl. Assume that the density and heat capacity of the solutions is the same as that of water.
Hint: Write a balanced reaction for the process.
A) -32 kJ/mol AgCl
B) -78 kJ/mol AgCl
C) -64 kJ/mol AgCl
D) -25 kJ/mol AgCl
E) -59 kJ/mol AgCl
43) Use the standard reaction enthalpies given below to determine ΔH°rxn for the following reaction:
P4(g) + 10 Cl2(g) → 4PCl5(s) ΔH°rxn = ?
Given:
PCl5(s) → PCl3(g) + Cl2(g) ΔH°rxn = +157 kJ
P4(g) + 6 Cl2(g) → 4 PCl3(g) ΔH°rxn = -1207 kJ
A) -1835 kJ
B) -1364 kJ
C) -1050. kJ
D) -1786 kJ
E) -2100. kJ
44) Use the standard reaction enthalpies given below to determine ΔH°rxn for the following reaction:
2 NO(g) + O2(g) → 2 NO2(g) ΔH°rxn = ?
Given:
N2(g) + O2(g) → 2 NO(g) ΔH°rxn = +183 kJ
1/2 N2(g) + O2(g) → NO2(g) ΔH°rxn = +33 kJ
A) -150. kJ
B) -117 kJ
C) -333 kJ
D) +115 kJ
E) +238 kJ
45) Use the standard reaction enthalpies given below to determine ΔH°rxn for the following reaction:
2 S(s) + 3 O2(g) → 2 SO3(g) ΔH°rxn = ?
Given:
SO2(g) → S(s) + O2(g) ΔH°rxn = +296.8 kJ
2 SO2(g) + O2(g) → 2 SO3(g) ΔH°rxn = -197.8 kJ
A) -494.6 kJ
B) -692.4 kJ
C) -791.4 kJ
D) 1583 kJ
E) -293.0 kJ
46) Use the standard reaction enthalpies given below to determine ΔH°rxn for the following reaction:
4 SO3(g) → 4 S(s) + 6 O2(g) ΔH°rxn = ?
Given:
SO2(g) → S(s) + O2(g) ΔH°rxn = +296.8 kJ
2 SO2(g) + O2(g) → 2 SO3(g) ΔH°rxn = -197.8 kJ
A) -494.6 kJ
B) -692.4 kJ
C) -791.4 kJ
D) 1583 kJ
E) -293.0 kJ
47) Which of the following is not a standard state?
A) for a solid, it is 25°F
B) for a liquid, it is 25°C
C) for a gas, it is 1 atm
D) for a solution, it is 1 M
E) for a liquid, it is 1 atm
48) Which of the following is not a standard state?
A) for a liquid, it is 25°F
B) for a solid, it is 25°C
C) for a solid, it is 1 atm
D) for a solution, it is 1 M
E) for a liquid, it is 1 atm
49) Choose the thermochemical equation that illustrates ΔH°f for Li2SO4.
A) 2 Li+(aq) + SO42-(aq) → Li2SO4(aq)
B) 2 Li(s) + 1/8 S8(s, rhombic) + 2 O2(g) → Li2SO4(s)
C) Li2SO4(aq) → 2 Li+(aq) + SO42-(aq)
D) 8 Li2SO4(s) → 16 Li(s) + S8(s, rhombic) + 16 O2(g)
E) 16 Li(s) + S8(s, rhombic) + 16 O2(g) → 8 Li2SO4(s)
50) Use the ΔH°f information provided to calculate ΔH°rxn for the following:
ΔH°f (kJ/mol) SO2Cl2(g) + 2 H2O(l) → 2 HCl(g) + H2SO4(l) ΔH°rxn = ?
SO2Cl2(g) -364
H2O(l) –286
HCl(g) -92
H2SO4(l) -814
A) -256 kJ
B) +161 kJ
C) -62 kJ
D) +800. kJ
E) -422 kJ
51) Use the ΔH°f and ΔH°rxn information provided to calculate ΔH°f for IF:
ΔH°f (kJ/mol) IF7(g) + I2(g) → IF5(g) + 2 IF(g) ΔH°rxn = -89 kJ
IF7(g) -941
IF5(g) -840
A) 101 kJ/mol
B) -146 kJ/mol
C) -190. kJ/mol
D) -95 kJ/mol
E) 24 kJ/mol
52) Use the ΔH°f and ΔH°rxn information provided to calculate ΔH°f for SO3(g):
ΔH°f (kJ/mol) 2 SO2(g) + O2(g) → 2 SO3(g) ΔH°rxn = -198 kJ
SO2(g) -297
A) -792 kJ/mol
B) -248 kJ/mol
C) -495 kJ/mol
D) -578 kJ/mol
E) -396 kJ/mol
53) Use the information provided to determine ΔH°rxn for the following reaction:
ΔH°f (kJ/mol) CH4(g) + 4 Cl2(g) → CCl4(g) + 4 HCl(g) ΔH°rxn = ?
CH4(g) -75
CCl4(g) -96
HCl(g) -92
A) -389 kJ
B) -113 kJ
C) +113 kJ
D) -71 kJ
E) +79 kJ
54) Use the information provided to determine ΔH°rxn for the following reaction:
ΔH°f (kJ/mol) CH4(g) + 3 Cl2(g) → CHCl3(l) + 3 HCl(g) ΔH°rxn = ?
CH4(g) -75
CHCl3(l) -134
HCl(g) -92
A) -151 kJ
B) -335 kJ
C) +662 kJ
D) +117 kJ
E) -217 kJ
55) Use the information provided to determine ΔH°rxn for the following reaction:
ΔH°f (kJ/mol) 3 Fe2O3(s) + CO(g) → 2 Fe3O4(s) + CO2(g) ΔH°rxn = ?
Fe2O3(s) -824
Fe3O4(s) -1118
CO(g) -111
CO2(g) -394
A) +277 kJ
B) -577 kJ
C) -47 kJ
D) +144 kJ
E) -111 kJ
56) Which of the following statements is TRUE?
A) The burning of fossil fuels contributes to global warming.
B) Cars that run on hydrogen fuel cells are environmentally friendly.
C) The more energy produced per kg of CO2 produced, the better the fuel.
D) Acid rain is one of the problems associated with the combustion of fossil fuels.
E) All of the above are true.
57) Which of the following is not a major contributor to energy consumption?
A) residential
B) commercial
C) transportation
D) industrial
E) atmospheric