Chapter 5 SCH 4U Questions
Modified True/False
Indicate whether the statement is true or false. If false, change the identified word or phrase to make the statement true.
____
1. Thermochemistry is the study of energy changes that accompany transformations in solids.
____________________
____
2. Energy transformations are the basis for all the activities that make up our lives. ____________________
____
3. Thermal energy is a form of potential energy that can be released to the surroundings.
____________________
____
4. Chemical systems contain both kinetic and potential forms of energy. ____________________
____
5. The energy of protons and neutrons in the atomic nuclei is a form of potential energy in a chemical system.
____________________
____
6. A negative enthalpy change is a measure of the amount of energy absorbed from the surroundings.
____________________
____
7. Temperature, theoretically, is a measure of the maximum kinetic energy of the molecules in a substance.
____________________
____
8. Inside a calorimeter, the amount of energy gained by the surroundings (the water) must equal the amount of
energy released by the reaction in the calorimeter. _____________________
____
9. The molar heat of reaction refers to the amount of heat needed to increase the temperature of one mole of a
substance by one degree Celsius. ____________________
____ 10. A chemical equation that represents a change in matter and includes the molar enthalpy is termed a
thermochemical equation. ____________________
____ 11. The enthalpy change per mole of a substance undergoing a change is called the molar enthalpy.
____________________
____ 12. Enthalpy changes for an exothermic reaction are given a negative sign. ____________________
____ 13. Enthalpy changes for an endothermic reaction are given a negative sign. ____________________
____ 14. The amount of energy involved in a change depends on the quantity of matter undergoing the change.
____________________
____ 15. If a chemical equation is reversed, according to Hess's Law, no change occurs to the H of the reaction.
____________________
____ 16. According to Hess's Law, if the coefficients of a chemical equation are altered by multiplying or dividing by a
constant factor, then the H is altered the same way. ____________________
____ 17. The following diagram represents an exothermic reaction. ____________________
____ 18. The reactants in a heat of formation reaction can be elements or compounds as long as they are in their
standard form. _________________________
____ 19. The major energy sources that we use in Ontario are all infinite. ____________________
____ 20. Uranium is a very concentrated energy source. ____________________
____ 21. CANDU reactors use natural uranium containing 50% uranium-235 and 50% uranium-238.
______________________________
____ 22. To date there have been no major nuclear accidents in Canada. ____________________
____ 23. Nuclear fusion occurs naturally in the sun. ____________________
____ 24. Uranium would be an ideal reactant for a nuclear fusion reaction. ____________________
Multiple Choice
Identify the choice that best completes the statement or answers the question.
____ 25. An exothermic reaction is one where
a. heat is transferred from the surroundings into a system
b. heat is transferred from a system into the surroundings
c. kinetic energy is transformed into potential energy
d. there is no transfer of heat
e. none of the above
____ 26. An endothermic reaction is one where
a. heat is transferred from the surroundings into a system
b. heat is transferred from a system into the surroundings
c. kinetic energy is transformed into potential energy
d. there is no transfer of heat
e. none of the above
____ 27. In an exothermic reaction, heat flows into the surroundings because
a. the potential energy of the chemicals increases
b. the kinetic energy of the chemicals decreases
c. the chemical potential energy is converted into heat energy
d. the chemical kinetic energy is converted into heat energy
e. none of the above
____ 28. In an exothermic reaction, the temperature of the surroundings increases because the molecules in the
surrounding have
a. a lower kinetic energy
b. a lower potential energy
c. a greater kinetic energy
d. a greater potential energy
e. not changed in either kinetic or potential energy
____ 29. A chemical system in which both energy and matter can flow into or out of a system is described as
a. a closed system
d. a chemical system
b. an open system
e. none of the above
c. an isolated system
____ 30. A chemical system in which neither energy nor matter can flow into or out of a system is described as
a. a closed system
d. a chemical system
b. an open system
e. none of the above
c. an isolated system
____ 31. A chemical system in which matter cannot flow into or out of a system is described as
a. a closed system
d. a chemical system
b. an open system
e. none of the above
c. an isolated system
____ 32. Which of the following is not a form of kinetic energy in a chemical system?
a. moving electrons within an atom
b. the vibration of atoms connected by chemical bonds
c. the rotation of molecules that make up the chemical system
d. the translation of molecules within the chemical system
e. the energy of protons and neutrons in atomic nuclei
____ 33. The specific heat capacity of a substance is
a. the quantity of heat required to raise the temperature of one mole of a substance by one
degree Celsius or Kelvin
b. the quantity of heat required to raise the temperature of one gram of a substance by one
degree Celsius or Kelvin
c. the quantity of heat required to raise the temperature of one molecule of a substance by
one degree Celsius or Kelvin
d. the quantity of heat required to raise the temperature of a substance by one degree Celsius
or Kelvin
e. none of the above
____ 34. An enthalpy change is
a. the difference in the kinetic energy of the reactants and the products in a chemical change
b. the difference in the potential energy of the reactants and the products in a chemical
change
c. the difference in enthalpies of the reactants and the products in a chemical change
d. the sum of the potential and kinetic energies of the products
e. the sum of the potential and kinetic energies of the reactants
____ 35. We can communicate the energy changes obtained from empirical studies by
a. including an energy value as a term in the thermochemical equation
b. writing a chemical equation and stating its enthalpy change
c. stating the molar enthalpy of a specific reaction
d. drawing a chemical potential energy diagram
e. any of the above
____ 36. Which statement concerning the Law of Conservation of Energy is not true?
a. it applies to all chemical changes
b. it involves all different forms of energy
c. it applies to nuclear reactions
d. it includes potential energy
e. it involves heat content of substances
____ 37. The molar heat of vaporization of water is 42 kJ/mol. How much energy is released by the condensation of
3.0 g of water?
a. 0.88 kJ
d. 250 kJ
b. 7.0 kJ
e. 0.07 kJ
c. 130 kJ
____ 38. What is another way to write the following equation?
C2H6(g)  C2H2(g) + 2H2(g) H = 3.2  102 kJ/mol
a.
b.
c.
d.
e.
C2H6(g)  C2H6(g) + 2H2(g) + 3.2  102 kJ
C2H6(g) + 3.2  102 kJ  C2H2(g) + 2H2(g)
2H2(g) + C2H2(g) + 3.2  102 kJ  C2H6(g)
C2H6(g) – 3.2  102 kJ  C2H2(g) + 2H2(g)
none of the above
____ 39. Which of the following reactions is exothermic?
a. H2(g) + 1/2 O2(g)  H2O(g) H = –243 kJ/mol
b. 1/2 N2(g) + 1/2 O2(g) + 90.7 kJ  NO(g)
c. CO(g) + 111 kJ C(s) + 1/2 O2(g)
d. 1/2 H2(g) + 1/2 I2(g)  HI(g) H = +26 kJ/mol
e. H2O(g) H2(g) + 1/2 O2(g) – H = –243 kJ/mol
____ 40. In a calorimeter, a 1.0 g sample of magnesium is burned to form MgO. In doing so, 25.5 kJ of energy are
released. What is the Heat of Combustion in kJ/mol of magnesium?
a. 306.2
d. 25.5
b. 1.54  1025
e. 620
c. 0.0392
____ 41. 1.00 mol of an element burned in a calorimeter raise the temperature of 100 g of water by 10.00 C. The molar
heat of combustion of the element is
a. 6.36 kJ/mol
d. 4.20 kJ/mol
b. 0.239 kJ/mol
e. 16.9 kJ/mol
c. 41.8 kJ/mol
____ 42. If the heat of formation of sodium chlorate is –53 kJ/mol, then the heat of reaction for 3 mol of sodium
chlorate is
a. –17.7 kJ
d. 159 kJ
b. 17.7 kJ
e. none of the above
c. –159 kJ
____ 43. Which statement concerning the accompanying diagram is true?
a.
b.
c.
d.
e.
H is positive
the system is endothermic
the system releases heat to the surroundings
the heat content of the reactants is less than the heat content of the products
the enthalpy of the products is greater than the enthalpy of reactants
____ 44. When a 'target' reaction can be expressed as the sum of other reactions, the heat of the 'target' reaction is the
sum of the enthalpy changes of the other reactions. This statement is referred to as
a. Law of Constant Composition
d. Priestly's Law
b. Law of Conservation of Energy
e. Boyle's Law
c. Hess's Law
____ 45. Given the following thermochemical data:
1. C2H2(g) + 5/2 O2(g)  2CO2(g) + H2O(l) H = –1.30  103 kJ
2. C2H6(g) + 7/2 O2 (g)  2CO2(g) + 3H2O(l) H = –1.56  103 kJ
3. H2(g) + 1/2 O2(g)  H2O (l) H = –2.86  102 kJ
What is H for the following reaction?
C2H2(g) + 2H2(g)  C2H6(g)
a. –2.60  101 kJ
b. –3.12  102 kJ
c. –5.72  102 kJ
d. –5.46  103 kJ
e. 2.60  101 kJ
____ 46. Consider the following four equations:
1. C6H6(l) + 15/2 O2(g)  6CO2(g) + 3H2O(l) )H1
2. H2(g) + 1/2 O2(g)  H2O(l) H2
3. C(s) + O2(g)  CO2(g) H3
4. 6C(s) + 3H2(g)  C6H6(l) H4
The enthalpy change for reaction 1, H1 can be obtained by combining the H's for the other reactions in
which of the following ways?
a. 6(H3) + 3(H2) + H4
d. 6(H3) + 3(H2) – H4
b. 6(H3) – 3(H2) + H4
e. none of the above
c. 6(H3) – 3(H2) + H4
____ 47. For which one of the following substances is the standard enthalpy of formation, Hf, equal to zero?
a. water [H2O(l)]
d. carbon dioxide [CO2(g)]
b. lead [Pb(s)]
e. tin [Sn(g)]
c. carbon dioxide [CO2(s)]
____ 48. Consider the following equation for the combustion of hydrogen:
H2(g) + 1/2 O2(g)  H2O(g) + 243 kJ
In order to produce 1215 kJ of heat, how many grams of H2 must burn?
a. 12.0 g
d. 0.250 g
b. 0.100 g
e. 8.00 g
c. 10.0 g
____ 49. When solid ammonium chloride, NH4Cl, is added to water, the temperature of the solution decreases. Which
statement best describes this observation?
a. The reaction is exothermic
b. Heat is released from the system, so it feels cooler.
c. NH4Cl(s) + H2O(l)  NH4Cl(aq) + 33.6 kJ
d. NH4Cl(s) + H2O(l)  NH4Cl(aq) H = +33.6 kJ
e. NH4Cl(s) does not dissolve in water.
____ 50. NaCl(s) + H2O(l)  NaCl(aq) H = +1.67 kJ/mol of NaCl (at 298 K)
If sufficient NaCl is dissolved in water to form 1.00 L of 2.00 mol/L NaCl solution, the change in enthalpy of
the system will be
a. 1.67 kJ
d. 2.50 kJ
b. 3.34 kJ
e. none of the above
c. 8.35 kJ
____ 51. Using the standard heats of formation, what is the enthalpy change per mole of CO2 for the following
reaction?
CO(g) + 1/2 O2(g)  CO2(g)
a. –506 kJ
b. –284 kJ
c. +284 kJ
d. +506 kJ
e. –617 kJ
____ 52. Based on the heat of formation of MgO, how much energy is required to decompose 48.6 g of MgO?
a. 603 kJ
d. 60.3 kJ
b. 725 kJ
e. 1504 kJ
c. 301 kJ
____ 53. The heat released during the combustion of C3H8(g) (propane) to produce CO2(carbon dioxide) gas and water
vapour is 2222 kJ/mol of C3H8(g). Which of the following is the correct chemical equation for the reaction?
a. C3H8(g) + 5O2(g)  3CO2(g) + 4H2O (g) H = +2222 kJ
b. C3H8(g) + 5O2(g) + 2222 kJ  4H2O (g) + 3CO2(g)
c. C3H8(g)+ 5O2(g)  3CO2(g) + 4H2O (g) + 2222 kJ
d. 3CO2(g) + 4H2O(g)  5O2(g) + C3H8(g) H = –2222 kJ
e. none of the above
____ 54. Which of the following equations represents the correct heat of formation of water vapour?
a. H2(g) + 1/2 O2(g)  H2O(l)
d. H2(g) + O2(g)  2H2O(g)
b. H2(g) + O(g)  H2O(g)
e. H2(g) + 1/2 O2(g)  H2O(g)
c. 2H(g) + O(g)  H2O(g)
____ 55. Consider the following exothermic reactions:
I. 2H(g)  H2(g) + heat
II. H2(g)  H2(s) + heat
III. H2(l)  H2(s) + heat
IV. 2H + 3H  4He + 1n + heat
What is the order of the reactions in magnitude of their expected H's?
a. II < III < IV < I
d. IV < II < I < III
b. IV < I < II < III
e. I < III < II < IV
c. III < II < I < IV
____ 56. Use the following data to determine the
a. –30.6 kJ
b. +30.6 kJ
c. –609.6 kJ
of vaporization for silicon tetrachloride at its boiling point.
d. +609.6 kJ
e. +1249.8 kJ
____ 57. A small 2.0-g candle is consumed in heating 100 g of water from 25ºC to 75ºC. If 200 g of water were heated
by the same candle, the temperature of the water would change from 25ºC would be about
a. 25ºC
d. 100ºC
b. 50ºC
e. 150ºC
c. 75ºC
____ 58. A small 2.0-g candle is consumed in heating 100 g of water from 25ºC to 75ºC. If two of the same candles are
used to heat 200 g of water, the temperature of the water after heating would have changed by
a. 25ºC
d. 100ºC
b. 50ºC
e. 150ºC
c. 75ºC
____ 59. A small 2.0-g candle is consumed in heating 100 g of water from 25ºC to 75ºC. If you ignore loss of heat to
the air, the energy produced per gram of the candle would be
a. 8.56 kJ
d. 2.62 kJ
b. 5.23 kJ
e. 20.65 kJ
c. 10.46 kJ
____ 60. Which one of the following statements about potential energy is false?
a. potential energy is released as a liquid solidifies
b. the reactants of an exothermic reaction contain more potential energy than the products
c. changes in potential energy are always recognizable by accompanying temperature
changes
d. potential energy is lowered when a bond forms
e. potential energy is stored in the water in a cloud
____ 61. Methyl alcohol both burns and evaporates. Use this information to determine which of these statements is
false.
a. the burning of methyl alcohol is an exothermic process
b. the intermolecular forces of methyl alcohol are weaker than the intramolecular forces
c. more heat is involved in burning methyl alcohol than in evaporating a mole of alcohol
d. the evaporation of methyl alcohol is an exothermic process
e. methyl alcohol can evaporate at temperatures below its boiling point
____ 62. The combustion of magnesium in air is very exothermic.
If the given two reactions and their heats of reaction were used to determine the heat of combustion of
magnesium the result would be
a. x + y
d. x – 2y
b. x – y
e. not enough information is given
c. 2x – y
____ 63. What is the range of the enthalpy change for a nuclear reaction?
a.
d.
b.
e.
c.
____ 64. What is the range of the enthalpy change for a chemical reaction?
a.
d.
b.
e.
c.
____ 65. What is the range of the enthalpy change for a physical reaction?
a.
d.
b.
e.
c.
Completion
Complete each statement.
66. In ____________________ changes, energy is released from a system to the surroundings.
67. In ____________________ changes, energy is absorbed by a system.
68. The amount of energy transferred between substances is known as ____________________.
69. ____________________ is a measure of the average kinetic energy of the particles in a sample of matter.
70. A system in which both matter and energy can move in or out is called a(n) ____________________ system.
71. An ideal system in which neither matter nor energy can move in or out is a(n) ____________________
system.
72. A system in which energy and not matter can move in or out is a(n) ____________________ system.
73. A _________________________ is a device in which a fuel is burned inside an insulated container to obtain
accurate measurements of heat transfers during chemical reactions.
74. Chemical systems have both ____________________ and ____________________ forms of energy.
75. The enthalpy change per mole of a substance undergoing a change is called the ____________________.
76. A ____________________ change typically has enthalpy changes in the range
77. A enthalpy change in the
.
kJ/mol probably was a ____________________ change.
78. A ____________________ change has a typical enthalpy change in the
kJ/mol
79. The magnitude of the energy change from a nuclear change is the result of ____________________ equation.
80. Enthalpy changes for exothermic reactions are given a ____________________ sign.
81. An enthalpy change for an endothermic reaction are given a ____________________ sign.
82. This statement, "The total energy change of the chemical system is equal to the total energy change of the
surroundings" is based on the ________________________________________.
83. A chemical equation that includes the energy term involved in the reaction is called a
____________________ equation.
84. A _________________________ diagram is a graphical representation of the energy transferred during a
physical or chemical change.
85. ____________________ states: The value of the
for any reaction that can be written in steps equals the
sum of the values of
for each of the individual steps.
86. A ____________________ reaction is a reaction in which compounds are formed from their elements.
87. The standard enthalpy of formation of an element already in its standard state is ____________________.
88. The most widely used nuclear reaction is the ____________________ of uranium into two smaller nuclei.
89. The potential energy of the products is ____________________ than the potential energy of the reactants in
an exothermic reaction.
Matching
Match these thermochemical terms with the following statements.
a.
b.
c.
d.
e.
f.
g.
thermal energy
chemical system
surroundings
heat
exothermic
enthalpy change
temperature
h.
i.
j.
k.
l.
m.
n.
open system
isolated system
closed system
calorimetry
bomb calorimeter
endothermic
molar enthalpy
____ 90. all matter around a system that is capable of absorbing or releasing thermal energy
____ 91. amount of energy transferred between substances
____ 92. a system in which energy can move in or out, but not matter
____ 93. a device in which a fuel is burned inside an insulated container to measure heat transfer during chemical
reactions
____ 94. energy available from a substance as a result of the motion of its molecules
____ 95. a set of reactants and products under study, usually represented by a chemical equation
____ 96. releasing thermal energy as heat flows out of the system
____ 97. an ideal system in which neither matter nor energy can move in or out
____ 98. absorbing thermal energy as heat flows into the system
____ 99. the technological process of measuring energy changes in a chemical system
____ 100. average kinetic energy of the particles in a sample of matter
____ 101. a system in which both matter and energy can move in or out
____ 102. the difference in enthalpies of reactants and products during a reaction
____ 103. the enthalpy change involving one mole of a substance
For each of the following statements, identify if the enthalpy change is a result of a physical, chemical or
nuclear change.
a. physical change
b. chemical change
c. nuclear change
____ 104. energy changes overcome the forces between protons and neutrons in nuclei
____ 105. typical enthalpy changes are in the range H = 102 – 104 kJ/mol
____ 106. temperature remains constant during changes of state
____ 107. energy changes overcome the electronic structure and chemical bonds within the particles.
____ 108. new atoms with different numbers of protons or neutrons are formed
____ 109. temperature changes during dissolving of pure substances
____ 110. new substances with new chemical bonding are formed
____ 111. fundamental particles remain unchanged at the molecular level
____ 112. typical enthalpy changes are in the range H = 100 – 102 kJ/mol
____ 113. energy is used to overcome or allow intermolecular forces to act
____ 114. typical enthalpy changes are in the range H = 1010 – 1012 kJ/mol
Short Answer
115. Explain the transfer of energy from an exothermic reaction to the surroundings of the system.
116. What are two reasons that energy changes in chemical systems are measured at standard conditions of
temperature and pressure such as SATP?
117. Explain why
.
118. Describe four different ways in which the enthalpy change associated with a chemical change can be
communicated.
119. Describe Hess's Law in your own words and include an example.
120. What are two rules that can be applied to chemical equations and enthalpy changes when using Hess's Law?
121. What are the steps involved in writing formation equations?
122. What are the three simplifying assumptions often used in calorimetry?
123. How are nuclear power stations and conventional power stations similar? How are they different?
124. Describe the process of nuclear fission of uranium.
125. Describe the process by which a medical cold pack works.
126. Dry ice is solid carbon dioxide. It does not melt, but instead it sublimes directly to the gas state.
a. Is this change endothermic or exothermic?
b. What sign would the
have?
c. Explain the transfer of energy involved in this change.
127. A kilogram of water and a kilogram of sand are at the same temperature. Do the two substances contain the
same amount of heat energy? Explain.
Problem
128. If an iron ring with a mass of 5.5 g changes temperature from 25.0ºC to 28.0ºC, how much energy has it
absorbed?
129. If 335 g of water at 24.5ºC absorbed 2.66 kJ of energy, what is the final temperature of the water?
130. Wind energy is becoming a more common form of energy that can be used to run household appliances.
a. If a windmill is connected to a hot water tank and is used to heat 60 L (60 kg) of water from 15ºC to 70ºC,
how much energy is required?
b. If energy from the utility company costs 0.35 cents per megajoule, how much money is saved in a year if
the water in the tank is heated 1400 times?
131. Calculate the enthalpy change,
for the vaporization of 200 g of methanol.
132. Farmers in the south often spray water on plants when there is a chance of frost to protect them from freezing.
Calculate the amount of heat released when 100 kg of water freezes at 0ºC.
133. 7.28 kJ of heat is released when 40.0 g of Br2 (bromine) vapour at 332 K condense to a liquid. What is the
molar heat of vaporization of Br2?
134. Consider the following equation for the combustion of H2(hydrogen):
H2(g) + 1/2O2(g)  H2O(g) + 243 kJ
In order to produce 972 kJ of heat, how many grams of H2 must burn?
135. Given the following information, determine the molar heat of vapourization of water.
H2(g) + 1/2 O2(g)  H2O(g) + 242.8 kJ
H2(g) + 1/2 O2(g)  H2O(l) + 286.9 kJ
136. The combustion of methanol is shown by the following equation:
i. Given the data which follows:
a. Find the heat of reaction for the equation above.
b. State the molar heat of combustion of methanol.
c. State whether the reaction is endothermic or exothermic.
ii. What mass of water could be heated from 20.00 C to 35.00 C by the burning of 2.57 mol of methanol? (
)
137. When sulfuric acid dissolves in water, a great deal of heat is given off. The enthalpy change for this process is
called the enthalpy of solution. To measure it, 175 g of water was placed in a coffee-cup calorimeter and
chilled to 10oC. Then 49.0 g of pure sulfuric acid, also at 10.0oC, was added, and the mixture was quickly
stirred with a thermometer. The temperature rose rapidly to 14.9oC. Assume that the value of the specific heat
of solution is 4.184 J/goC. You may assume that the specific heat of the resulting sulfuric acid solution will
also be 4.184 J/goC. Calculate q for the formation of this solution and the enthalpy of solution in kilojoules
per mole of H2SO4.
138. Ethanol, C2H5OH, is made industrially by the reaction of water with ethylene, C2H44. Calculate the value of
Ho for the reaction
C2H4(g) + H2O(l)  C2H5OH(l)
given the following thermochemical equations:
C2H4(g) + 3 O2(g)  2 CO2(g) + 2 H2O(l) Ho = –1411.1 kJ
C2H5OH(l) + 3 O2(g)  2 CO2(g) + 3 H2O(l) Ho = –1367.1 kJ
139. What is the Ho in kilojoules for the combustion of 1 mol of ethanol, C2H5OH(l), to form gaseous carbon
dioxide and gaseous water?
140. If one mole of water absorbs 44 kJ of heat as it changes state from liquid to gas, calculate the amount of heat
that is absorbed if 200 g of water is evaporated.
141. The thermite reaction is quite a common reaction and is spectacular. Iron (III) oxide and metallic aluminum
produce iron and aluminum oxide in a few seconds. Find H for this reaction given the following
information.
142. Copper metal can be produced by heating copper(II) oxide and hydrogen gas (and other product of the
reaction is water). If the enthalpy of reaction (
) for this reaction is +130.5 kJ, calculate the heat of reaction
for producing 2.0 g of copper metal.
143. a. Calculate
Ho for the following reaction.
b. State whether the reaction is exothermic or endothermic.
c. Rewrite the equation as a thermochemical equation to include the heat term.
d. Indicate whether the products have a greater or smaller enthalpy than the reactants.
Essay
144. Outline some of the arguments both for and against the use of nuclear power.
145. "In the 1950s, people had high expectations of endless, inexpensive nuclear energy". Discuss this statement in
terms of what changes have occurred that this has yet to come to fruition.
Chapter 5 SCH 4U Questions
Answer Section
MODIFIED TRUE/FALSE
1. ANS: F, matter
PTS:
2. ANS:
OBJ:
3. ANS:
1
T
5.1
F, kinetic
OBJ: 5.1
PTS: 1
STA: ECV.01
REF: K/U
PTS:
4. ANS:
OBJ:
5. ANS:
OBJ:
6. ANS:
1
REF: K/U
T
5.1
STA: EC2.02
T
5.1
STA: EC2.01
F, released to
OBJ: 5.1
PTS: 1
STA: ECV.01
REF: K/U
PTS: 1
REF: K/U
OBJ: 5.1
STA: EC2.02
1
REF: K/U
T
5.1
STA: EC2.02
F, molar heat capacity
OBJ: 5.1
PTS: 1
STA: EC2.01
REF: K/U
1
REF:
T
5.2
STA:
T
5.2
STA:
T
5.2
STA:
F, positive sign
OBJ: 5.1
PTS: 1
STA: EC2.01
REF: K/U
PTS: 1
REF: K/U
PTS: 1
REF: K/U
PTS: 1
7. ANS: F, average
PTS:
8. ANS:
OBJ:
9. ANS:
10.
11.
12.
13.
PTS:
ANS:
OBJ:
ANS:
OBJ:
ANS:
OBJ:
ANS:
REF: K/U
STA: ECV.01
REF: K/U
K/U
EC2.02
EC2.02
EC2.02
PTS:
14. ANS:
OBJ:
15. ANS:
1
REF: K/U
T
5.2
STA: EC2.02
F, sign is reversed
OBJ: 5.2
PTS: 1
STA: EC2.02
REF: K/U
PTS:
16. ANS:
OBJ:
17. ANS:
1
REF: K/U
T
5.4
STA: EC1.02
F, endothermic
OBJ: 5.4
PTS: 1
STA: EC1.02
REF: K/U
OBJ: 5.3
STA: EC1.05
PTS: 1
REF: K/U
18. ANS: F, elements only
PTS: 1
19. ANS: F, finite
REF: K/U
OBJ: 5.5
STA: EC2.05
PTS:
20. ANS:
OBJ:
21. ANS:
1
REF: K/U
T
5.6
STA: EC3.01
F, 0.7% U-235 and 99.3% U-238
OBJ: 5.6
PTS: 1
STA: EC3.01
REF: K/U
PTS:
22. ANS:
OBJ:
23. ANS:
OBJ:
24. ANS:
1
T
5.6
T
5.6
F, hydrogen
OBJ: 5.6
PTS: 1
STA: EC3.01
REF: K/U
PTS: 1
REF: K/U
REF: K/U
OBJ: 5.6
STA: EC3.01
PTS: 1
REF: K/U
OBJ: 5.1
PTS: 1
REF: K/U
OBJ: 5.1
PTS: 1
REF: K/U
OBJ: 5.1
PTS: 1
REF: K/U
OBJ: 5.1
PTS: 1
REF: C
OBJ: 5.1
PTS: 1
REF: C
OBJ: 5.1
PTS: 1
REF: C
OBJ: 5.1
PTS: 1
REF: K/U
OBJ: 5.1
PTS: 1
REF: K/U
OBJ: 5.1
PTS: 1
REF: K/U
OBJ: 5.1
PTS: 1
REF: K/U
OBJ: 5.3
PTS: 1
REF: K/U
OBJ: 5.2
PTS: 1
REF: I
OBJ: 5.2
PTS: 1
REF: C
OBJ: 5.3
PTS: 1
REF: K/U
STA: EC3.01
STA: EC3.01
MULTIPLE CHOICE
25. ANS:
STA:
26. ANS:
STA:
27. ANS:
STA:
28. ANS:
STA:
29. ANS:
STA:
30. ANS:
STA:
31. ANS:
STA:
32. ANS:
STA:
33. ANS:
STA:
34. ANS:
STA:
35. ANS:
STA:
36. ANS:
STA:
37. ANS:
STA:
38. ANS:
B
ECV.01
A
ECV.01
C
ECV.01
C
ECV.01
B
EC2.01
C
EC2.02
A
EC2.02
E
EC1.05
B
EC2.01
A
EC2.01
E
EC2.02
C
EC1.02
B
EC2.03
B
STA:
39. ANS:
STA:
40. ANS:
STA:
41. ANS:
STA:
42. ANS:
STA:
43. ANS:
STA:
44. ANS:
STA:
45. ANS:
STA:
46. ANS:
STA:
47. ANS:
STA:
48. ANS:
STA:
49. ANS:
STA:
50. ANS:
STA:
51. ANS:
STA:
52. ANS:
STA:
53. ANS:
STA:
54. ANS:
STA:
55. ANS:
STA:
56. ANS:
STA:
57. ANS:
STA:
58. ANS:
STA:
59. ANS:
STA:
60. ANS:
STA:
61. ANS:
STA:
62. ANS:
STA:
EC2.02
A
EC2.02
E
EC2.03
D
EC2.03
C
EC2.03
C
EC1.05
C
EC1.02
B
EC2.04
D
EC2.04
B
EC2.05
C
EC2.03
D
EC2.03
B
EC2.04
B
EC2.05
B
EC2.05
C
EC2.02
E
EC2.05
C
EC1.01
B
EC2.03
A
EC2.03
B
EC2.03
C
EC2.03
C
EC1.05
D
ECV.01
E
EC2.04
PTS: 1
REF: C
OBJ: 5.3
PTS: 1
REF: I
OBJ: 5.2
PTS: 1
REF: I
OBJ: 5.2
PTS: 1
REF: I
OBJ: 5.3
PTS: 1
REF: C
OBJ: 5.3
PTS: 1
REF: K/U
OBJ: 5.4
PTS: 1
REF: I
OBJ: 5.4
PTS: 1
REF: I
OBJ: 5.4
PTS: 1
REF: K/U
OBJ: 5.5
PTS: 1
REF: I
OBJ: 5.3
PTS: 1
REF: K/U
OBJ: 5.3
PTS: 1
REF: I
OBJ: 5.3
PTS: 1
REF: I
OBJ: 5.5
PTS: 1
REF: I
OBJ: 5.5
PTS: 1
REF: C
OBJ: 5.3
PTS: 1
REF: C
OBJ: 5.5
PTS: 1
REF: K/U
OBJ: 5.1
PTS: 1
REF: I
OBJ: 5.2
PTS: 1
REF: K/U
OBJ: 5.2
PTS: 1
REF: K/U
OBJ: 5.2
PTS: 1
REF: I
OBJ: 5.2
PTS: 1
REF: K/U
OBJ: 5.1
PTS: 1
REF: K/U
OBJ: 5.1
PTS: 1
REF: I
OBJ: 5.4
63. ANS:
STA:
64. ANS:
STA:
65. ANS:
STA:
C
EC1.01
B
EC1.01
C
EC1.01
PTS: 1
REF: K/U
OBJ: 5.1
PTS: 1
REF: K/U
OBJ: 5.1
PTS: 1
REF: K/U
OBJ: 5.1
PTS: 1
67. ANS: endothermic
REF: K/U
OBJ: 5.1
STA: ECV.01
PTS: 1
68. ANS: heat
REF: K/U
OBJ: 5.1
STA: ECV.01
PTS: 1
REF: C
69. ANS: Temperature
OBJ: 5.1
STA: EC2.01
PTS: 1
70. ANS: open
REF: C
OBJ: 5.1
STA: EC2.01
PTS: 1
71. ANS: isolated
REF: C
OBJ: 5.1
STA: EC2.01
PTS: 1
72. ANS: closed
REF: C
OBJ: 5.1
STA: EC2.01
PTS: 1
REF: C
73. ANS: bomb calorimeter
OBJ: 5.1
STA: EC2.01
PTS: 1
REF: K/U
74. ANS: kinetic, potential
OBJ: 5.1
STA: ECV.02
PTS: 1
REF: K/U
75. ANS: molar enthalpy
OBJ: 5.1
STA: EC2.01
PTS: 1
76. ANS: physical
REF: K/U
OBJ: 5.2
STA: EC2.02
PTS: 1
77. ANS: chemical
REF: K/U
OBJ: 5.1
STA: EC1.01
PTS: 1
78. ANS: nuclear
REF: K/U
OBJ: 5.1
STA: EC1.01
PTS: 1
79. ANS: Einstein's
REF: K/U
OBJ: 5.1
STA: EC1.01
COMPLETION
66. ANS: exothermic
PTS: 1
80. ANS: negative
REF: K/U
OBJ: 5.1
STA: EC1.01
PTS: 1
81. ANS: positive
REF: K/U
OBJ: 5.2
STA: EC2.02
PTS: 1
REF: K/U
82. ANS: Law of Conservation of Energy
OBJ: 5.1
STA: EC2.02
PTS: 1
REF: K/U
83. ANS: thermochemical
OBJ: 5.2
STA: EC2.03
PTS: 1
REF: K/U
84. ANS: potential energy
OBJ: 5.3
STA: EC2.02
PTS: 1
85. ANS: Hess's Law
REF: K/U
OBJ: 5.3
STA: EC1.05
PTS: 1
86. ANS: formation
REF: K/U
OBJ: 5.4
STA: EC1.02
PTS: 1
87. ANS:
zero
0
REF: K/U
OBJ: 5.5
STA: EC2.05
PTS: 1
88. ANS: fission
REF: K/U
OBJ: 5.5
STA: EC2.05
PTS: 1
89. ANS: lower
REF: K/U
OBJ: 5.6
STA: EC3.01
PTS: 1
REF: K/U
OBJ: 5.3
STA: EC1.05
PTS: 1
REF: K/U
OBJ: 5.1
PTS: 1
REF: K/U
OBJ: 5.1
PTS: 1
REF: K/U
OBJ: 5.1
PTS: 1
REF: K/U
OBJ: 5.1
PTS: 1
REF: K/U
OBJ: 5.1
PTS: 1
REF: K/U
OBJ: 5.1
MATCHING
90. ANS:
STA:
91. ANS:
STA:
92. ANS:
STA:
93. ANS:
STA:
94. ANS:
STA:
95. ANS:
STA:
C
EC2.01
D
EC2.01
J
EC2.01
L
EC2.01
A
EC2.01
B
EC2.01
96. ANS:
STA:
97. ANS:
STA:
98. ANS:
STA:
99. ANS:
STA:
100. ANS:
STA:
101. ANS:
STA:
102. ANS:
STA:
103. ANS:
STA:
E
EC2.01
I
EC2.01
M
EC2.01
K
EC2.01
G
EC2.01
H
EC2.01
F
EC2.01
N
EC2.01
PTS: 1
REF: K/U
OBJ: 5.1
PTS: 1
REF: K/U
OBJ: 5.1
PTS: 1
REF: K/U
OBJ: 5.1
PTS: 1
REF: K/U
OBJ: 5.1
PTS: 1
REF: K/U
OBJ: 5.1
PTS: 1
REF: K/U
OBJ: 5.1
PTS: 1
REF: K/U
OBJ: 5.2
PTS: 1
REF: K/U
OBJ: 5.2
104. ANS:
STA:
105. ANS:
STA:
106. ANS:
STA:
107. ANS:
STA:
108. ANS:
STA:
109. ANS:
STA:
110. ANS:
STA:
111. ANS:
STA:
112. ANS:
STA:
113. ANS:
STA:
114. ANS:
STA:
C
EC1.01
B
EC1.01
A
EC1.01
B
EC1.01
C
EC1.01
A
EC1.01
B
EC1.01
A
EC1.01
A
EC1.01
A
EC1.01
C
EC1.01
PTS: 1
REF: K/U
OBJ: 5.1
PTS: 1
REF: K/U
OBJ: 5.1
PTS: 1
REF: K/U
OBJ: 5.1
PTS: 1
REF: K/U
OBJ: 5.1
PTS: 1
REF: K/U
OBJ: 5.1
PTS: 1
REF: K/U
OBJ: 5.1
PTS: 1
REF: K/U
OBJ: 5.1
PTS: 1
REF: K/U
OBJ: 5.1
PTS: 1
REF: K/U
OBJ: 5.1
PTS: 1
REF: K/U
OBJ: 5.1
PTS: 1
REF: K/U
OBJ: 5.1
SHORT ANSWER
115. ANS:
- some of the chemical potential energy in the system is converted initially to increase the kinetic energy of
the products
- through collisions, this kinetic energy is transferred to the particles in the surroundings, which results in a
raise in temperature (i.e., average kinetic energy of the molecules) of the surroundings
PTS: 1
REF: C
OBJ: 5.1
STA: EC1.04
116. ANS:
1. In order to control variables and to allow comparisons between different reactions.
2. Under these conditions, the enthalpy change of a chemical system is the change in the chemical potential
energy of the system because the kinetic energy of the system's molecules stay constant.
PTS: 1
REF: C
OBJ: 5.1
STA: EC2.01
117. ANS:
Due to the Law of Conservation of Mass, the total amount of energy in the system must remain constant;
consequently, the enthalpy change of the system must be equal in magnitude, but opposite in sign to the
energy released to or absorbed from the surroundings.
PTS: 1
REF: K/U
OBJ: 5.1
STA: EC2.02
118. ANS:
1. inclusion of the energy term within the chemical reaction
as a reactant if reaction is endothermic
as a product if reaction is exothermic
2. inclusion of a
term at end of the equation
3. inclusion of the molar enthalpy of reaction with the equation
4. a potential energy diagram can be used to described the enthalpy change
PTS: 1
REF: C
OBJ: 5.3
STA: EC2.02
119. ANS:
Hess's law is a method of determining the enthalpy of a 'target' reaction from two or more reactions for which
the enthalpy change is known.
By adding the enthalpy changes of the known reactions, the enthalpy of the 'target' reaction can be calculated.
Example:
PTS: 1
REF: C
OBJ: 5.4
STA: EC1.02
120. ANS:
- if a chemical equation is reversed, then the sign of the
changes
- if the coefficients of a chemical equation are altered by multiplying or dividing by a constant factor, then
the
is altered in the same way
PTS: 1
REF: C
OBJ: 5.4
STA: EC1.02
121. ANS:
- write one mole of product in the state that has been specified
- write the reactant elements in their standard state
- choose equation coefficients for the reactants to give a balanced equation yielding one mole of products
PTS: 1
REF: C
OBJ: 5.4
STA: EC2.05
122. ANS:
- no heat is transferred between the calorimeter and the outside environment
- any heat absorbed or released by the calorimeter materials, such as the container, is negligible
- a dilute aqueous solution is assumed to have a density and specific heat capacity equal to that of pure water
PTS: 1
REF: C
OBJ: 5.2
STA: EC2.03
123. ANS:
- in both systems, heat is used to boil water and the resulting steam drives a turbine
- the spinning turbines, in turn, drive generators that produce electricity
- the difference is that in a conventional power station, combustion of natural gas, oil, or coal supplies the
heat and in a nuclear power station, nuclear fission provides the heat
PTS: 1
REF: C
OBJ: 5.6
STA: EC3.01
124. ANS:
- the process is initiated by relatively slow-moving neutrons hitting a uranium nucleus, releasing large
amounts of energy
- more neutrons are also generated that are able to collide with yet more uranium nuclei to generate even
more heat energy
PTS: 1
REF: C
OBJ: 5.6
STA: EC3.01
125. ANS:
- a medical cold pack operates on the principle that certain salts dissolve endothermically in water
- as the salt dissolves, it absorbs energy from the water when they dissolve in water
- as a result, the cold pack becomes cold
PTS: 1
REF: C
OBJ: 5.1
STA: EC3.02
126. ANS:
a. endothermic
b. positive
c. the energy required for the reaction would be taken from the air surrounding the dry ice
as particles from the air collide with the dry ice, energy would be passed to the ice causing it to sublime
PTS: 1
REF: K/U
OBJ: 5.2
STA: EC1.01
127. ANS:
No. Since the water and sand have very different heat capacities, they would contain significantly different
amounts of heat energy.
PTS: 1
REF: I
PROBLEM
128. ANS:
m=
c=
T =
=
q=
=
=
5.5 g
0.444 J/gºC
28.0ºC – 25.0ºC
3.0ºC
mcT
(5.5 g)(0.444 J/gºC)(3.0ºC)
7.3 J
7.3 J of energy has been absorbed.
OBJ: 5.2
STA: EC2.01
PTS: 1
129. ANS:
m=
q=
=
c=
T1 =
REF: I
OBJ: 5.1
STA: EC2.03
335 g
2.66 kJ
2660 J
4.18 J/(g·ºC)
24.5ºC
The final temperature of the water would be 26.4ºC.
PTS: 1
130. ANS:
a.
REF: I
OBJ: 5.1
STA: EC2.03
13.8 MJ of energy is required to heat the water in the hot water tank.
b.
Approximately $67 would be saved over the course of the year on the hot water tank.
PTS: 1
131. ANS:
REF: I
OBJ: 5.1
STA: EC3.01
Find the number of moles of methanol
Then find the enthalpy change
Since the methanol vaporizes by absorbing heat, the enthalpy change is +244.8 kJ.
PTS: 1
132. ANS:
REF: I
OBJ: 5.2
STA: EC2.03
Calculate the number of moles of water:
Calculate the enthalpy change
33.4 MJ of heat would be released (to protect the plants) when 100 kg of water freezes.
PTS: 1
REF: I
OBJ: 5.2
133. ANS:
Calculate the number of moles of Bromine
STA: EC2.03
Calculate the molar enthalpy
The molar heat of vaporization of Br2 is 29.1 kJ/mol.
PTS: 1
REF: I
OBJ: 5.2
134. ANS:
Determine the number of moles of H2 that are required.
STA: EC2.03
Calculate the mass of H2 required
8.08 g of H2 would need to be burned.
PTS: 1
REF: I
OBJ: 5.3
135. ANS:
Show the addition of equations to get and thus appropriate
H2O(l)  H2O(g)
H2(g) + 1/2 O2(g)  H2O(g)
H2O(l)  H2(g) + 1/2 O2(g)
H2O(l)  H2O(g)
STA: EC2.03
values
The molar heat of vaporization of water is 44.1 kJ/mol based on the given information.
PTS: 1
136. ANS:
i. a.
REF: I
OBJ: 5.4
STA: EC2.04
=[(2  –393 kJ) + (4  –242 kJ)] – [2  –638 kJ]
= –478 kJ
The heat of reaction for the equation is –478 kJ
b. Since this is for 2 moles of methanol,
= –478 kJ /2 mol
= –239 kJ/mol
The molar heat of combustion of methanol is –239 kJ/mol
c. Since the value is negative, the reaction is exothermic
ii.
since q = –
q = 614 kJ
= 150 C
c= 4.184 kJ/kg0 C
9.78 kg of water could be heated with 2.57 mol of methanol.
PTS: 1
REF: I
137. ANS:
Calculate q for the reaction
m = mass of water + sulfuric acid
= 175 g + 49 g
= 224 g
OBJ: 5.5
STA: EC2.05
o
T = 4.9 C
q=
=
=
=
mc)T
(224 g)(4.184 J/goC)(4.9oC)
4592 J
4.59 kJ
since
H = –4.59 kJ
Calculate number of moles of sulfuric acid
The enthalpy of solution for sulfuric acid is –9.18 kJ/mol.
PTS: 1
REF: I
OBJ: 5.2
138. ANS:
Show the addition of equations to give "target" reaction
C2H4(g) + 3 O2(g)  2 CO2(g) + 2 H2O(l)
STA: EC2.03
Ho = –1411.1 kJ
2 CO2(g) + 3 H2O(l)  C2H5OH(l) + 3 O2(g)
Ho = +1367.1 kJ
________________________________________________________________
C2H4(g) + H2O(l)  C2H5OH(l)
Ho = –44 kJ
The Ho for the reaction is 44 kJ.
PTS: 1
REF: I
OBJ: 5.4
139. ANS:
First write and balance the combustion equation.
C2H5OH(l) + 3 O2(g)  2 CO2(g) + 3 H2O(g)
Hess's law for this equation is:
Ho = [(2)CO2(g) + (3)H2O(g)] – [C2H5OH(l) + (3)O2(g)]
STA: EC2.04
= [ (2)–393.5 + (3)–241.8 kJ/mol] – [ –235.2 + (3)0 kJ/mol]
= [–787 –725.4 kJ/mol ] – [ –235.2 kJ/mol ]
= –1512.4 + 235.2 kJ/mol
= –1277.2 kJ/mol
The reaction for the combustion of ethanol is exothermic by 1277.2 kJ/mol.
PTS: 1
REF: I
140. ANS:
Calculate the number of moles of water
OBJ: 5.4
STA: EC2.04
Calculate heat
4.9 x 102 kJ of heat would be absorbed in the evaporation.
PTS: 1
REF: I
141. ANS:
Determine equation for thermite reaction:
OBJ: 5.2
STA: EC2.02
Rearrange given equations to add to add to target equation
The H the reaction is –848 kJ.
PTS: 1
REF: I
OBJ: 5.4
STA: EC2.04
142. ANS:
Determine balanced thermochemical equation.
Determine the number of moles of copper.
Determine heat of reaction for 0.31 mol
The heat of reaction to produce 2.0 g of copper is 4.1 kJ
PTS: 1
143. ANS:
a.
REF: I
OBJ: 5.3
STA: EC2.02
The heat of reaction is –907 kJ/mol of Benzene
b. Since the sign of the heat of reaction is negative, the reaction is exothermic.
c.
d. Since the reaction is exothermic, the products would have a smaller enthalpy than the reactants, since
energy is given off to the surroundings.
PTS: 1
REF: I
OBJ: 5.5
STA: EC2.05 | EC2.02
ESSAY
144. ANS:
Advocates:
- has low uranium fuel costs, including transportation
- causes very little air pollution, such as green house and acid gases
- reduces our dependence on fossil fuels for electricity generation, allowing those materials to be used for
other purposes.
Opponents:
- the possible release of radioactive materials in a reactor malfunction
- the difficulty of disposing of the highly toxic radioactive wastes
- the large capital costs of building nuclear reactors and then decommissioning them at the end of their
relatively short lifetime
- unknown health effects of long-term low level exposure to radiation
- thermal pollution from cooling water
PTS: 1
REF: I
OBJ: 5.6
STA: EC3.01
145. ANS:
Students answers should include some of the following points:
Arguments from the opponents of nuclear waste including:
- possible reactor malfunction
- disposal of radioactive waste
- large capital costs of building reactors
- unknown long-term effects
Also, some accidents in the recent past, have also slowed the more recent development of nuclear power
stations including:
- the near-accident at Three Mile Island in 1979
- the nuclear explosion at Chernobyl in Ukraine in 1986
Moreover, the development of nuclear fusion has yet to be advanced to be a useable source.
PTS: 1
REF: I
OBJ: 5.6
STA: EC3.01