Name ______________________________________ Date ____________ Class _______________________
Modern Chemistry • CHAPTER 17
HOMEWORK 17-1 (pp. 511–517)
1. Explain the difference between temperature and heat. ____________________________________________________
_________________________________________________________________________________________________
_________________________________________________________________________________________________
2. VOCABULARY
A. Choose the term from Column B that is most closely related to each term in Column A. Write the
letter of the term you choose in the space at the right.
Column A
Column B
____1. exothermic
a. ∆ H
____2. endothermic
b. thermochemical
____3. enthalpy
c. gives off heat
____4. heat of reaction
d. absorbs heat
e. amount of energy released or absorbed as heat
B. Write true or false.
____________1. The molar heat of formation refers to the heat released or absorbed when a compound decomposes
into its elements.
____________2. A compound has a high negative heat of formation if a large amount of energy is released when the
compound is formed.
____________3. Compounds with highly positive values of heats of formation are stable compounds.
____________4. The heat of combustion is the heat released by the complete combustion of one mole of a substance.
____________5. A combustion calorimeter can be used to determine heats of combustion.
3. Graphic Organizer
A. Use the words absorbed, exothermic, positive, negative, endothermic, and released to complete the chart.
Type of Reaction
Enthalpy of Reaction
Heat is
B. This chart shows standard enthalpies of formation in kcal/mol for various substances. Write
whether the formation of each substance is an exothermic or endothermic reaction.
Substance
∆ H (kcal/mol)
Exothermic or Endothermic
AlCl3(s)
–167.4
HCl(g)
–22.1
NO(g)
21.6
O3(g)
34.0
MgO(s)
–143.8
Name ______________________________________ Date ____________ Class _______________________
Modern Chemistry • CHAPTER 17
HOMEWORK 17-1 (pp. 511–517)
4. MULTIPLE CHOICE
Choose the letter of the best answer.
______1. Which should not be included in a thermochemical equation?
A. number of molecules of reactants
B. physical state of the products
C. number of moles of reactants
D. coefficients that are fractions
______2. Which statement is not true?
A. A chemical equation does not tell you the heat that is involved in a reaction.
B. A system must be at constant pressure in order to measure the enthalpy.
C. Fractional coefficients can be used in thermochemical reactions.
D. The enthalpy of a system can be measured directly.
5. Use the above chart to answer the next 3 questions.
________________________A. Which compound is most stable? Include the physical state.
________________________B. Which compound (including physical state) is least stable?
C. Use the values in the chart to draw a general conclusion about the stabilities of various states of matter.
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6. In each group, which is the most stable compound?
__________a. NH3
Ca(OH)2
FeCl2
__________b. Na2SO4
K2SO4
MgSO4
7. In each group, which is the least stable compound?
__________a. NH3
K2SO4
SO3
__________b. Ca(OH)2
N2O3
LiNO3
Name ______________________________________ Date ____________ Class _______________________
Modern Chemistry • CHAPTER 17
HOMEWORK 17-1 (pp. 511–517)
1. Temperature is a measure of the average kinetic energy of particles, while heat is the total kinetic
energy of all particles in a sample of matter.
VOCABULARY
1. c
2. d
3. a
4. e
VOCABULARY AND SKILL BUILDER
1. false
2. true
3. false
4. true
5. true
GRAPHIC ORGANIZERS
Enthalpy and Heat
Type of Reaction Enthalpy of Reaction Heat
exothermic negative released
endothermic positive absorbed
Substance Δ H Exothermic or Endothermic
AlCl3(s) –167.4 exothermic
HCl(g) –22.1 exothermic
NO(g) 21.6 endothermic
O3(g) 34.0 endothermic
MgO(s) –143.8 exothermic
STANDARDIZED TEST PREP
1. a
2. d
CHAPTER 17 •
HOMEWORK 17-3
SKILL BUILDER
1. solid potassium sulfate
2. ethyne gas
3. In general, solids are more stable than liquids and gases.
4. a. Ca(OH)2
b. K2SO4
5. a. NH3
b. N2O3
STANDARDIZED TEST PREP
1. a
2. c