Chemistry: The Central Science, 12e (Brown et al.)
Chapter 5 Thermochemistry
5.1 Multiple Choice Questions
1) At what velocity (m/s) must a 20.0 g object be moving in order to possess a kinetic energy of 1.00 J?
A) 1.00
B) 100 × 102
C) 10.0
D) 1.00 × 103
E) 50.0
2) Objects can possess energy as __________.
(a) endothermic energy
(b) potential energy
(c) kinetic energy
A) a only
B) b only
C) c only
D) a and c
E) b and c
3) The internal energy of a system is always increased by __________.
A) adding heat to the system
B) having the system do work on the surroundings
C) withdrawing heat from the system
D) adding heat to the system and having the system do work on the surroundings
E) a volume compression
4) The internal energy of a system __________.
A) is the sum of the kinetic energy of all of its components
B) is the sum of the rotational, vibrational, and translational energies of all of its components
C) refers only to the energies of the nuclei of the atoms of the component molecules
D) is the sum of the potential and kinetic energies of the components
E) none of the above
5) Which one of the following conditions would always result in an increase in the internal energy of a
system?
A) The system loses heat and does work on the surroundings.
B) The system gains heat and does work on the surroundings.
C) The system loses heat and has work done on it by the surroundings.
D) The system gains heat and has work done on it by the surroundings.
E) None of the above is correct.
6) The value of ΔE for a system that performs 111 kJ of work on its surroundings and gains 89 kJ of
heat is __________ kJ.
A) -111
B) -200
C) 200
D) -22
E) 22
7) The value of ΔE for a system that performs 13 kJ of work on its surroundings and loses 9 kJ of heat is
__________ kJ.
A) 22
B) -22
C) -4
D) 4
E) -13
8) When a system __________, ΔE is always negative.
A) absorbs heat and does work
B) gives off heat and does work
C) absorbs heat and has work done on it
D) gives off heat and has work done on it
E) none of the above is always negative.
9) Which one of the following is an endothermic process?
A) ice melting
B) water freezing
C) boiling soup
D) Hydrochloric acid and barium hydroxide are mixed at 25 °C: the temperature increases.
E) Both A and C
10) Which one of the following is an exothermic process?
A) ice melting
B) water evaporating
C) boiling soup
D) condensation of water vapor
E) Ammonium thiocyanate and barium hydroxide are mixed at 25 °C: the temperature drops.
11) Of the following, which one is a state function?
A) H
B) q
C) w
D) heat
E) none of the above
12) Which of the following is a statement of the first law of thermodynamics?
A) Ek = (1/2) mv2
B) A negative ΔH corresponds to an exothermic process.
C) ΔE = Efinal – Einitial
D) Energy lost by the system must be gained by the surroundings.
E) 1 cal = 4.184 J (exactly)
13) The internal energy can be increased by __________.
(a) transferring heat from the surroundings to the system
(b) transferring heat from the system to the surroundings
(c) doing work on the system
A) a only
B) b only
C) c only
D) a and c
E) b and c
14) A __________ ΔH corresponds to an __________ process.
A) negative, endothermic
B) negative, exothermic
C) positive, exothermic
D) zero, exothermic
E) zero, endothermic
15) A __________ ΔH corresponds to an __________ process.
A) negative, endothermic
B) positive, exothermic
C) positive, endothermic
D) zero, exothermic
E) zero, endothermic
16) ΔH for an endothermic process is __________ while ΔH for an exothermic process is __________.
A) zero, positive
B) zero, negative
C) positive, zero
D) negative, positive
E) positive, negative
17) For a given process at constant pressure, ΔH is negative. This means that the process is
__________.
A) endothermic
B) equithermic
C) exothermic
D) a state function
E) energy
18) Which one of the following statements is true?
A) Enthalpy is an intensive property.
B) The enthalpy change for a reaction is independent of the state of the reactants and products.
C) Enthalpy is a state function.
D) H is the value of q measured under conditions of constant volume.
E) The enthalpy change of a reaction is the reciprocal of the ΔH of the reverse reaction.
19) Which of the following statements is false?
A) Internal energy is a state function.
B) Enthalpy is an intensive property.
C) The enthalpy change for a reaction is equal in magnitude, but opposite in sign, to the enthalpy change
for the reverse reaction.
D) The enthalpy change for a reaction depends on the state of the reactants and products.
E) The enthalpy of a reaction is equal to the heat of the reaction.
20) A chemical reaction that absorbs heat from the surroundings is said to be __________ and has a
__________ ΔH at constant pressure.
A) endothermic, positive
B) endothermic, negative
C) exothermic, negative
D) exothermic, positive
E) exothermic, neutral
21) A chemical reaction that releases heat to the surroundings is said to be __________ and has a
__________ ΔH at constant pressure.
A) endothermic, positive
B) endothermic, negative
C) exothermic, negative
D) exothermic, positive
E) exothermic, neutral
22) The reaction
4Al (s) + 3O2 (g) → 2 Al2O3 (s) ΔH° = -3351 kJ
is __________, and therefore heat is __________ by the reaction.
A) endothermic, released
B) endothermic, absorbed
C) exothermic, released
D) exothermic, absorbed
E) thermoneutral, neither released nor absorbed
23) Under what condition(s) is the enthalpy change of a process equal to the amount of heat transferred
into or out of the system?
(a) temperature is constant
(b) pressure is constant
(c) volume is constant
A) a only
B) b only
C) c only
D) a and b
E) b and c
24) The units of of heat capacity are __________.
A) K/J or °C/J
B) J/K or J/°C
C) J/g-K or J/g-°C
D) J/mol
E) g-K/J or g-°C/J
25) The units of of specific heat are __________.
A) K/J or °C/J
B) J/K or J/°C
C) J/g-K or J/g-°C
D) J/mol
E) g-K/J or g-°C/J
26) The British thermal unit (Btu) is commonly used in engineering applications. A Btu is defined as
the amount of heat required to raise the temperature of 1 lb of water by 1 °F. There are __________
joules in one Btu. 1 lb = 453.59 g; °C = (5/9)(°F – 32°); specific heat of H2O (l) = 4.184 J/g-K.
A) 3415
B) 60.29
C) 1054
D) 5.120 × 10-3
E) Additional information is needed to complete the calculation.
27) A sample of calcium carbonate [CaCO3 (s)] absorbs 45.5 J of heat, upon which the temperature of
the sample increases from 21.1 °C to 28.5 °C. If the specific heat of calcium carbonate is 0.82 J/g-K,
what is the mass (in grams) of the sample?
A) 3.7
B) 5.0
C) 7.5
D) 410
E) 5.0 x 103
28) The temperature of a 12.58 g sample of calcium carbonate [CaCO3 (s)] increases from 23.6 °C to
38.2 °C. If the specific heat of calcium carbonate is 0.82 J/g-K, how many joules of heat are absorbed?
A) 0.82
B) 5.0
C) 7.5
D) 410
E) 151
29) An 8.29 g sample of calcium carbonate [CaCO3 (s)] absorbs 50.3 J of heat, upon which the
temperature of the sample increases from 21.1 °C to 28.5 °C. What is the specific heat of calcium
carbonate?
A) .63
B) .82
C) 1.1
D) 2.2
E) 4.2
30) A sample of iron absorbs 67.5 J of heat, upon which the temperature of the sample increases from
21.5 °C to 28.5 °C. If the specific heat of iron is 0.450 J/g-K, what is the mass (in grams) of the sample?
A) 4.3
B) 11
C) 21
D) 1100
E) 1.1 x 103
31) The temperature of a 35.2 g sample of iron increases from 23.7 °C to 29.5 °C. If the specific heat of
iron is 0.450 J/g-K, how many joules of heat are absorbed?
A) 4.3
B) 92
C) 0.450
D) 1100
E) 1.1 x 103
32) A 22.44 g sample of iron absorbs 180.8 J of heat, upon which the temperature of the sample
increases from 21.1 °C to 39.0 °C. What is the specific heat of iron?
A) 0.140
B) 0.450
C) 0.820
D) 0.840
E) 0.900
33) Which of the following is a statement of Hess’s law?
A) If a reaction is carried out in a series of steps, the ΔH for the reaction will equal the sum of the
enthalpy changes for the individual steps.
B) If a reaction is carried out in a series of steps, the ΔH for the reaction will equal the product of the
enthalpy changes for the individual steps.
C) The ΔH for a process in the forward direction is equal in magnitude and opposite in sign to the ΔH
for the process in the reverse direction.
D) The ΔH for a process in the forward direction is equal to the ΔH for the process in the reverse
direction.
E) The ΔH of a reaction depends on the physical states of the reactants and products.
34) For which one of the following reactions is ΔH°rxn equal to the heat of formation of the product?
A) N2 (g) + 3H2 (g) → 2NH3 (g)
B) (1/2) N2 (g) + O2 (g) → NO2 (g)
C) 6C (s) + 6H (g) → C6H6 (l)
D) P (g) + 4H (g) + Br (g) → PH4Br (l)
E) 12C (g) + 11H2 (g) + 11O (g) → C6H22O11 (g)
35) Of the following, ΔHf° is not zero for __________.
A) O2 (g)
B) C (graphite)
C) N2 (g)
D) F2 (s)
E) Cl2 (g)
36) Of the following, ΔHf° is not zero for __________.
A) Sc (g)
B) Si (s)
C) P4 (s, white)
D) Br2 (l)
E) Ca (s)
37) Consider the following two reactions:
A → 2B ΔH°rxn = 456.7 kJ/mol
A → C ΔH°rxn = -22.1kJ/mol
Determine the enthalpy change for the process:
2B → C
A) -478.8 kJ/mol
B) -434.6 kJ/mol
C) 434.6 kJ/mol
D) 478.8 kJ/mol
E) More information is needed to solve the problem.
38) In the reaction below, ΔHf° is zero for __________.
Ni (s) + 2CO (g) + 2PF3 (g) → Ni(CO)2 (PF3)2 (l)
A) Ni (s)
B) CO (g)
C) PF3 (g)
D) Ni(CO)2(PF3)2 (l)
E) both CO (g) and PF3 (g)
39) For the species in the reaction below, ΔHf° is zero for __________.
2Co (s) + H2 (g) + 8PF3 (g) → 2HCo(PF3)4 (l)
A) Co (s)
B) H2 (g)
C) PF3 (g)
D) HCo(PF3)4 (l)
E) both Co(s) and H2 (g)
40) For which one of the following equations is ΔH°rxn equal to ΔHf° for the product?
A) Xe (g) + 2 F2 (g) → XeF4 (g)
B) CH4 (g) + 2 Cl2 (g) → CH2 Cl2 (l) + 2HCl (g)
C) N2 (g) + O3 (g) → N2O3 (g)
D) 2CO (g) + O2 (g) → 2CO2 (g)
E) C (diamond) + O2 (g) → CO2 (g)
41) For which one of the following reactions is the value of ΔH°rxn equal to ΔHf° for the product?
A) 2Ca (s) + O2 (g) → 2CaO (s)
B) C2H2 (g) + H2 (g) → C2H4 (g)
C) 2C (graphite) + O2 (g) → 2CO (g)
D) 3Mg (s) + N2 (g) → Mg3N2 (s)
E) C (diamond) + O2 (g) → CO2 (g)
42) For which one of the following reactions is the value of ΔH°rxn equal to ΔHf° for the product?
A) 2 C (s, graphite) + 2 H2 (g) → C2H4 (g)
B) N2 (g) + O2 (g) → 2 NO (g)
C) 2 H2 (g) + O2 (g) → 2 H2O (l)
D) 2 H2 (g) + O2 (g) → 2 H2O (g)
E) H2O (l) + 1/2 O2 (g) → H2O2 (l)
43) For which one of the following reactions is the value of ΔH°rxn equal to ΔH°f for the product?
A) H2O (l) + 1/2 O2 (g) → H2 O2 (l)
B) N2 (g) + O2 (g) → 2NO (g)
C) 2H2 (g) + O2 (g) → 2H2O (l)
D) 2H2 (g) + O2 (g) → 2H2O (g)
E) none of the above
44) For which one of the following reactions is the value of ΔH°rxn equal to ΔH°f for the product?
A) H2 (g) + 1/2 O2 (g) → H2O (l)
B) H2 (g) + O2 (g) → H2O2 (l)
C) 2 C (s, graphite) + 2 H2 (g) → C2H4 (g)
D) 1/2 N2 (g) + O2 (g) → NO2 (g)
E) all of the above
45) With reference to enthalpy changes, the term standard conditions means __________.
(a) P = 1 atm
(b) some common temperature, usually 298 K
(c) V = 1 L
A) a only
B) b only
C) c only
D) a and c
E) a and b
46) The energy released by combustion of 1 g of a substance is called the __________ of the substance.
A) specific heat
B) fuel value
C) nutritional calorie content
D) heat capacity
E) enthalpy
47) Fuel values of hydrocarbons increase as the H/C atomic ratio increases. Which of the following
compounds has the highest fuel value?
A) C2H6
B) C2H4
C) C2H2
D) CH4
E) C6H6
48) Of the substances below, the highest fuel value is obtained from __________.
A) charcoal
B) bituminous coal
C) natural gas
D) hydrogen
E) wood
49) Which one of the choices below is not considered a fossil fuel?
A) anthracite coal
B) crude oil
C) natural gas
D) hydrogen
E) petroleum
50) The most abundant fossil fuel is __________.
A) natural gas
B) petroleum
C) coal
D) uranium
E) hydrogen
5.2 Bimodal Questions
1) Calculate the kinetic energy in J of an electron moving at 6.00 × 106 m/s. The mass of an electron is
9.11 × 10-28 g.
A) 4.98 × 10-48
B) 3.28 × 10-14
C) 1.64 × 10-17
D) 2.49 × 10-48
E) 6.56 × 10-14
2) Calculate the kinetic energy in joules of an automobile weighing 2135 lb and traveling at 55 mph.
A) 1.2 × 104
B) 2.9 × 105
C) 5.9 × 105
D) 3.2 × 106
E) 3.2 × 10-6
3) Calculate the kinetic energy in joules of an automobile weighing 4345 lb and traveling at 75 mph.
A) 5.5 x 105
B) 5.5 × 10-5
C) 1.1 × 106
D) 2.2 × 106
E) 2.2 × 10-6
4) The kinetic energy of a 7.3 kg steel ball traveling at 18.0 m/s is __________ J.
A) 1.2 × 103
B) 66
C) 2.4 × 103
D) 1.3 × 102
E) 7.3
5) The kinetic energy of a 10.3 g golf ball traveling at 48.0 m/s is __________ J.
A) 1.20 × 103
B) 66
C) 11.9
D) 1.3 × 102
E) 23.7
6) Calculate the kinetic energy in joules of a 150 lb jogger (68.1 kg) traveling at 12.0 mile/hr (5.36 m/s).
A) 1.96 × 103
B) 365
C) 978
D) 183
E) 68.1
7) Calculate the kinetic energy in joules of an 80.0 g bullet traveling at 300.0 m/s.
A) 3.60 × 106
B) 1.20 × 104
C) 3.60 × 103
D) 12.0
E) 80.0
8) The kinetic energy of a 23.2-g object moving at a speed of 81.9 km/hr is __________ J.
A) 1900
B) 77.8
C) 145
D) 1.43 × 10-3
E) 6.00
9) The kinetic energy of a 23.2-g object moving at a speed of 81.9 km/hr is __________ kcal.
A) 1.43 × 10-3
B) 6.00
C) 1900
D) 454
E) 0.0251
10) A 100-watt electric incandescent light bulb consumes __________ J of energy in 24 hours. [1 Watt
(W) = 1 J/sec]
A) 2.40 × 103
B) 8.64 × 103
C) 4.17
D) 2.10 × 103
E) 8.64 × 106
11) The ΔE of a system that releases 12.4 J of heat and does 4.2 J of work on the surroundings is
__________ J.
A) 16.6
B) 12.4
C) 4.2
D) -16.6
E) -8.2
12) The ΔE of a system that absorbs 12.4 J of heat and does 4.2 J of work on the surroundings is
__________ J.
A) 16.6
B) 12.4
C) 4.2
D) -16.6
E) 8.2
13) The change in the internal energy of a system that absorbs 2,500 J of heat and that does 7,655 J of
work on the surroundings is __________ J.
A) 10,155
B) 5,155
C) -5,155
D) -10,155
E) 1.91 ×
14) The change in the internal energy of a system that releases 2,500 J of heat and that does 7,655 J of
work on the surroundings is __________ J.
A) -10,155
B) -5,155
C) -1.91 × 107
D) 10,155
E) 5,155
15) The value of ΔH° for the reaction below is -72 kJ. __________ kJ of heat are released when 80.9
grams of HBr is formed in this reaction.
H2 (g) + Br2 (g) → 2HBr (g)
A) 144
B) 72
C) 0.44
D) 36
E) -72
16) The value of ΔH° for the reaction below is -126 kJ. __________ kj are released when 2.00 mol of
NaOH is formed in the reaction?
2 Na2O2 (s) + 2 H2O (l) → 4NaOH (s) + O2 (g)
A) 252
B) 63
C) 3.9
D) 7.8
E) -126
17) The value of ΔH° for the reaction below is -790 kJ. The enthalpy change accompanying the reaction
of 0.95 g of S is __________ kJ.
2S (s) + 3O2 (g) → 2SO3 (g)
A) 23
B) -23
C) -12
D) 12
E) -790
18) The value of ΔH° for the reaction below is -6535 kJ. __________ kJ of heat are released in the
combustion of 16.0 g of C6H6 (l)?
2 C6H6 (l) + 15 O2 (g) → 12CO2 (g) + 6 H2O (l)
A) 1.34 ×
B) 5.23 ×
C) 669
D) 2.68 ×
E) -6535
19) The value of ΔH° for the reaction below is -482 kJ. Calculate the heat (kJ) released to the
surroundings when 38.5 g of O2 (g) reacts with excess CO.
2CO (g) + O2 (g) → 2CO2 (g)
A) 2.65 ×
B) 482
C) 580.
D) 65.7
E) 210.
20) The value of ΔH° for the reaction below is -336 kJ. Calculate the heat (kJ) released to the
surroundings when 23.0 g of HCl is formed.
CH4 (g) + 3 Cl2 (g) → CHCl3 (l) + 3HCl (g)
A) 177
B) 2.57 × 103
C) 70.7
D) 211
E) -336
18
21) The value of ΔH° for the reaction below is -186 kJ. Calculate the heat (kJ) released from the
reaction of 25 g of Cl2.
H2 (g) + Cl2 (g) → 2HCl (g)
A) 66
B) 5.3 ×
C) 33
D) 47
E) -186
22) The enthalpy change for the following reaction is -483.6 kJ:
2 H2 (g) + O2 (g) → 2 H2O (g)
Therefore, the enthalpy change for the following reaction is __________ kJ:
4 H2 (g) + 2 O2 (g) → 4 H2O (g)
A) -483.6
B) -967.2
C) 2.34 × 105
D) 483.6
E) 967.2
23) The value of ΔH° for the reaction below is +128.1 kJ:
CH3OH (l) → CO (g) + 2 H2 (g)
How many kJ of heat are consumed when 15.5 g of CH3OH (l) decomposes as shown in the equation?
A) 0.48
B) 62.0
C) 1.3 ×
D) 32
E) 8.3
24) The value of ΔH° for the reaction below is +128.1 kJ:
CH3OH (l) → CO (g) + 2 H2 (g)
How many kJ of heat are consumed when 5.10 g of H2 (g) is formed as shown in the equation?
A) 162
B) 62.0
C) 128
D) 653
E) 326
25) The value of ΔH° for the reaction below is +128.1 kJ:
CH3OH (l) → CO (g) + 2 H2 (g)
How many kJ of heat are consumed when 5.10 g of CO (g) is formed as shown in the equation?
A) 0.182
B) 162
C) 8.31
D) 23.3
E) 62.0
26) The value of ΔH° for the reaction below is +128.1 kJ:
CH3OH (l) → CO (g) + 2H2 (g)
How many kJ of heat are consumed when 5.75 g of CO (g) is formed as shown in the equation?
A) 23.3
B) 62.0
C) 26.3
D) 162
E) 8.3
27) The value of ΔH° for the reaction below is -1107 kJ:
2Ba (s) + O2 (g) → 2BaO (s)
How many kJ of heat are released when 5.75 g of Ba (s) reacts completely with oxygen to form
BaO (s)?
A) 96.3
B) 26.3
C) 46.4
D) 23.2
E) 193
28) The value of ΔH° for the reaction below is -1107 kJ:
2Ba (s) + O2 (g) → 2BaO (s)
How many kJ of heat are released when 5.75 g of BaO (s) is produced?
A) 56.9
B) 23.2
C) 20.8
D) 193
E) 96.3
29) The value of ΔH° for the reaction below is -1107 kJ:
2Ba (s) + O2 (g) → 2BaO (s)
How many kJ of heat are released when 15.75 g of Ba (s) reacts completely with oxygen to form BaO
(s)?
A) 20.8
B) 63.5
C) 114
D) 70.3
E) 35.1
30) The molar heat capacity of a compound with the formula C2H6SO is 88.0 J/mol-K. The specific
heat of this substance is __________ J/g-K.
A) 88.0
B) 1.13
C) 4.89
D) 6.88 ×
E) -88.0
31) The specific heat capacity of lead is 0.13 J/g-K. How much heat (in J) is required to raise the
temperature of 15 g of lead from 22 °C to 37 °C?
A) 2.0
B) -0.13
C) 5.8 × 10-4
D) 29
E) 0.13