Chapter(s) _
Name _____________________
Period _____
Set I: Energy
1. Use dimensional analysis to convert the following:
a. 9.32 J = _____ calories
2.23 calories
b. 73 Cal = _____ calories
73000 calories
c. 18 calories = _____ J
75.24 J
2. Determine whether the following describes kinetic energy (KE) or potential energy (PE)
PE a) A stretched out rubber band
PE b) Energy stored between C and O in CO
KE c) Light
PE d) Gravitational Potential Energy
KE e) Sound
PE f) Compressed spring
PE g) Nuclear Energy
KE h) Mechanical Motion
Transformation of Energy: The law of conservation of energy says that energy can not be created nor
destroyed, it simply changes form. For questions 3-5, Identify the answer choice that has the correct
energy transformation:
3. Toaster
a. chemical to thermal
b. electrical to thermal
c. thermal to chemical
d. thermal to electrical
4. Car Engine
a. chemical to mechanical
b. thermal to chemical
c. thermal to mechanical
d. mechanical to chemical
5.
Identify the correct statement:
a. Heat is being transferred from
b. Heat is being transferred from
c. Heat is being transferred from
d. Heat is being transferred from
the
the
the
the
system to the surroundings.
surroundings to the system.
system to the surroundings.
surroundings to the system.
The
The
The
The
process
process
process
process
is
is
is
is
endothermic.
endothermic.
exothermic.
exothermic.
6. The following reaction is exothermic: 2Na(s) + Cl2(g)  2NaCl(s) + Heat
a) What is the sign of the ΔH for this reaction?
negative
remember EXO = Hproducts < Hreactants
b) Is the enthalpy/heat of the product greater of less than that of the reactants?
less than
remember EXO = Hproducts < Hreactants
c) Does this reaction represent the formation of bonds or breaking of bonds?
formation of bonds
7. Consider the following reaction: S(s) + O2(g)  SO2(g) ΔH = -297 kJ
a) Is the reaction exothermic or endothermic?
exothermic
remember EXO = Hproducts < Hreactants
b) How does the enthalpy/heat of the product compare to that of the reactants?
less than
remember EXO = Hproducts < Hreactants
c) What is the value of ΔH for the reverse reaction?
positive 297 kJ
d) Does this reaction represent the formation of bonds or breaking of bonds?
formation of bonds
8. Consider the following process: H2O(g)  H2O(l) ΔH = -40.7 kJ/rxn
a) What type of physical change is occurring above?
condensation
b) Is this change endothermic or exothermic? How do you know? exothermic (- value)
c) Write the thermochemical equation H2O(g)  H2O(l) + 40.7 kJ
Set II: Calorimetry
Reference Data
Specific Heat Values
1 cal = 4.18 J
1 Calorie = 1000 calories
Substance
Water
Ice
Steam
Aluminum
Glass
Iron
Copper
Gold
stainless steel
olive oil
Specific Heat (J/goC)
4.18
2.1
1.7
0.90
0.50
0.46
0.39
0.13
0.50
2.0
1. Determine how much heat it would take to heat a 150.g block of each of the following substances by
10.0oC.
Q = mcT
Q = (150g)(specific heat)(10C)
a. ice
3150 J
d. copper
585 J
b. aluminum
1350 J
e. gold
195 J
c. glass
750 J
2. Determine the temperature change when a 150. g block of each of the following is supplied with
1.00 x 103 J of heat. Q /(m*c) = T
a. ice
3.17C
c. copper
17.1C
b. aluminum
7.41C
d. gold
51.3
3. You have 3 identical pans made out of each of the following substances. You place them on your cooktop on high in order to reach a reasonable 175oC sauté temperature. Which pan would reach the sauté
temperature first?
a. aluminum .90J/gC
b. copper
.39 J/gC (heats fastest)
c. stainless steel.50 J/gC
4. You place identical pans made of each of the following materials in your oven. After 5 minutes, which
pan will be the coldest? (Assume none of them have reached oven temperature yet.)
a. aluminum
b. copper
c. stainless steel
0.90J/gC (heats slowest)
0.39 J/gC
0.50 J/gC
5. A 4.0 g sample of glass was heated from 4oC to 21oC. How much heat did the glass absorb?
34.0J
m = 4.0g
T = 21C - 4C = 17C
Cp = 0.50 J/gC
Q = (4.0g) (.50 J/gC) (17C) = 34.0J
6. A sample of an unknown metal has a mass of 120.7g. As the sample cools from 90.5oC to 25.7oC, it
releases 7020 J of energy. Identify the metal.
0.89 J/gC = aluminum
m= 4.0g
T = 25.7C -90.5C = -64.8C
Q= -7020J
Cp = ? J/gC
Cp = -7020J / 120.7g/ -64.8C = 0.89 J/gC = aluminum
7. A 15.6 g sample of water absorbs 868 J as it is heated. If the initial temperature of the water was
21.5oC, what is the final temperature?
Tf = 34.8C
m= 15.6g
T = Tf – Ti = Tf – 21.5C
Q= 868J
Cp = 4.18 J/gC
T = Q / m / Cp = 868J / 15.6g / (4.18J/gC) = 13.3C
Tf = 13.3C + 21.5C
Tf = 34.8C
8. When a 50.0 g piece of nickel absorbs 350.0 J of heat, the temperature of the nickel changes from
20.0°C to 36.0°C. What is the specific heat of nickel?
0.438 J/g°C = (50.0 g) c (36.0°C-20.0°C) = 350.0 J
9. Calculate the quantity of heat that must be removed from 200.0 g of ethyl alcohol to cool it from 10.0°C
to 25.0°C.
7350 kJ = (200.0 g)(2.45 J/goC)( 25.0°C-10.0°C)
Set III: Thermochemical Equations
1. The chemical reaction 2H2O + energy  2H2 + O2 is
a. An endothermic reaction
b. A synthesis reaction
c. An exothermic reaction
d. A nuclear reaction
2. The chemical reaction CH4(g) + 2O2(g)  CO2(g) + 2H2O(g)
a. An endothermic reaction
b. A single replacement reaction
c. An exothermic reaction
d. A nuclear reaction
∆H = -802.3 kJ/rxn is
3. Consider the following reaction: 2CO(g) + O2(g)  2CO2(g) ∆H =-135.28 kcal
a. How much heat would be released if 12.0 moles of CO reacted with sufficient oxygen to
produce carbon dioxide?
12 mol CO x 135.28 kcal = 811.68 kcal
2 mol CO
b. If 575 kcal is released, how many moles of CO must have reacted?
575 kcal x 2 mol CO = 8.5 moles
135.28 kcal
4. Which enthalpy diagram shows that the reaction
A2(g) + X2(g)  2AX(g)
is an exothermic reaction that produces 550 kJ of heat?
A.
C.
B.
D.
B. starts with a high energy, ends with low energy. This means energy is released (exothermic)
***alternative questions for diagrams above.
Identify each diagram an showing an exothermic or endothermic reaction, and calculate the ΔH based on
the values on the y-axis.
Use the chart of Standard Enthalpies of Formation in your notes to answer the following questions:
5. Calculate the enthalpy change for the following reaction: 2SO3(g)  2 SO2(g) + O2(g)
ΔH =Σ Hproducts – Σ Hreactants
[ (2 x SO2) + (1 x O2)] - [2 x SO3]
=
[ (2 x -296.1kJ/mol) + (1 x 0)] - [2 x -395.2 kJ/mol]
= 198.2 kJ/rxn
6. Calculate the enthalpy change for the following reaction: S(s) + O2(g)  SO2(g)
ΔH =Σ Hproducts – Σ Hreactants
[ 1 x SO2] - [(1 x S) + (1 x O2)]
=
[ 1 x -296.1 kJ/mol] - [(1 x 0) + (1 x 0)]
= -296.1 kJ/mol
Review: Thermochemistry
Objectives to be tested include, but are not exclusive to:
 understand energy and its forms, including kinetic, potential, chemical, and thermal energies
 understand the law of conservation of energy and the processes of heat transfer
 use thermochemical equations to calculate energy changes that occur in chemical reactions and classify
reactions as exothermic or endothermic
 perform calculations involving heat, mass, temperature change, and specific heat
 use calorimetry to calculate the heat of a chemical process.
Practice
If you work the following problems on separate paper, staple it onto this packet before you lose it!
1) Riding a Bike
a) chemical to thermal
b) electrical to thermal
c) chemical to mechanical
d) mechanical to electrical
2) Consider the following reaction: 2H2(g) + O2(g)  2H2O(l) ΔH = -572 kJ/rxn
a) Is the reaction exothermic or endothermic? exothermic
b) How does the enthalpy/heat of the product compare to that of the reactants?
Heat reactants > heat products
c) Does this reaction represent the formation of bonds or breaking of bonds?
Forming
d) Is this reaction a synthesis, decomposition, single replacement, or double replacement?
synthesis
e) Write the thermochemical equation.
2H2(g) + O2(g)  2H2O(l) + 572 kJ
3) How much heat is required to raise the temperature of 32.4 g of mercury from 20˚C to 98˚C. The
specific heat of mercury is 0.140 J/g˚C.
354 J
4) How much heat would be absorbed by 25 g of mercury when it is heated from 11˚C to 100˚C?
312 J
5) If I applied the same amount of heat to 25 g of water, 25 g of aluminum, and 25 g of silver, which one
would heat up the fastest? Why?
Silver would heat up the fastest because it has the lowest specific heat.
6) Consider the following reaction: C6H12O6(s) + 6O2(g)  6CO2(g) + 6 H2O(l) ∆H =-2808 kJ kcal
a) How much energy would be used if 0.300 moles of C6H12O6 is burned in sufficient oxygen?
0.300 mol C6H12O6 x
2808 kJ = 842.4 kJ
1 mol C6H12O6
Use the chart of Standard Enthalpies of Formation in your notes to answer the following questions:
7) Calculate the enthalpy change for the following reaction: 2CO(g) + 2NO(g)  2 CO2(g) + N2(g)
ΔH =Σ Hproducts – Σ Hreactants
[ (2 x CO2)+(1 x N2)] - [(2 x CO) + (2 x NO)]
=
[ (2 x -393.5)+(1 x 0)] - [(2 x -110.5) + (2 x 90.4)] = -746.8
Chem I
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