Name______________________________________
Chapter 10
Period__________
Thermochemistry
Date___________
Review Worksheet
1. A 22.2 g sample of silver absorbs 65.5 J of heat energy when its temperature is raised from 31.0 C to 43.5 C. Find the
specific heat of the silver.
2. Fill in the sign of H and circle exothermic or endothermic to match the sign of H.
a) 2 K (s) + 1 Br2 (l)  2 KBr (s) + E
H = _______ exo / endo
b) 2 H2O (l) + E  2 H2 (g) + 1 O2 (g)
H = _______ exo / endo
3. Match the following phrases with the best response.
_____ a. Enthalpy for a physical change
_____ b. Equivalent to 1 calorie
_____ c. Tfinal - Tinitial
_____ d. Stored in bonds between atoms
_____ e. Capacity to do work
1. T
2. Energy
3. Hvaporization
4. 4.18 J
5. chemical potential energy
4. How much heat (in J) must be applied to a 25.0 g sample of Cu to raise its temperature by 20.0 C? (CCu is 0.385 J/g C)
5. A 35.2 g sample of metal Z is placed in a test tube and then into a boiling water bath for 15 minutes. The temperature of the
boiling water is 100.0 C. A Styrofoam calorimeter is prepared with 75.0 mL of distilled water in it. The initial temperature of
the water is 21.6 C. The hot metal is quickly transferred into the calorimeter and the final temperature of the metal & water is
28.2 C. Calculate the specific heat capacity of metal Z.
6. Are the following processes exothermic or endothermic?
a) When solid ammonium chloride, NH 4Cl, is added to water, the solution gets very cold. exo / endo
b) Gasoline burns in a car engine. exo / endo
c) When concentrated sulfuric acid is added to water, the solution gets very hot. exo / endo
d) H2O(l)  H2O(g) at 100 C exo / endo
e) Steam from a hot shower condenses on a cold mirror in the bathroom. exo / endo
7. Propane gas (C3H8) burns in oxygen to produce carbon dioxide gas and water. H for this reaction is –2221 kJ.
Write and balance the equation, including H, for this reaction, and answer the following questions.
Balanced equation: ____________________________________________________________________________________________________________
a) How much heat energy is produced if 35.00 grams of propane burns?
b) How much heat energy is produced if 100.0 liters of oxygen at STP reacts?
thermo_rev_ws.doc
Name______________________________________
Period__________
Date___________
c) How many moles of propane are required to produce enough energy to heat a bathtub filled with 1.0 x 106 grams of water
from 20.0 C to 85C? Hint: Use the calorimetry equation to calculate the joules of energy required to heat the bathtub
water first. Convert that into kJ. Then use your balanced equation to figure out how many moles of propane are required
to make that much energy.
d) Calculate the energy produced if 20.0 moles of propane reacts with 50.0 moles of oxygen.
8. What is the driving force for every spontaneous exothermic reaction?
9. What is the driving force for every spontaneous endothermic reaction?
10. In an exothermic reaction, the reactants have higher PE than the products. When an endothermic reaction occurs, the
system (gives off/ takes in) energy from the surroundings, and the surroundings (give off/ take in) energy from the system.
11. Fill in the blanks with the sign (+ or -) that you would expect for H and S for each of the following processes:
H
S
a) combustion of gasoline
b) melting of ice, H2O(s)  H2O(l)
c) CO2(s) → CO2(g)
d) electrolysis of water to oxygen & hydrogen gas
e) condensation of water vapor, H2O(g)  H2O(l)
f) the beaker gets hot when sulfuric acid is added to water
g) your skin feels cool when sweat evaporates (skin is system)
12. An ice cube is placed on the lab table in front of you and begins to melt.
a) Identify the system and the surroundings. System =
Surroundings =
b) Is energy going into or out of the system?
c) Is the reaction endothermic or exothermic?
e) In order for this reaction to be spontaneous, what must T be (high, low, any)?
f) Draw a heat content diagram that shows the direction of energy flow (reactants  products)
13. a) What is the symbol for temperature?
b) What are the SI units for temperature?
c) What is the symbol for heat?
d) What are the SI units for heat?
e) What is the equation that relates temperature to heat?
thermo_rev_ws.doc
Potential Energy
d) Is entropy, ∆S, positive or negative (increasing or decreasing)?
reactants  products
Name______________________________________
Period__________
Date___________
Standards Practice: Chemical Thermodynamics
1. Heat energy is transferred through
A. Active transport
B. Entropy
C. Molecules
D. Temperature
2. When temperature drops,
A. Energy increases.
B. Molecules move slower.
C. Collisions occur more often
D. Entropy increases.
3. Heating a substance increases
A. Atomic motion.
B. Molecular motion.
C. Both atomic and molecular motion.
D. Neither atomic nor molecular motion.
4. Circle all the endothermic reactions.
A. Breaking a chemical bond
B. Combustion of wood
C. Evaporating water
D. Making ice
5. Which is an exothermic reaction?
A. Boiling an egg
B. Mixing magnesium and a strong acid
C. Melting an ice cube
D. Evaporating water
6. In order for a reaction to be called exothermic,
A. The enthalpy of the reactants must be less
than that of the products.
B. The sign of the change in enthalpy for the
reactants must be positive.
C. The enthalpy of the products must be less
than that of the reactants.
D. Heat must flow from surroundings into the
system.
7. Fusion, or melting, is an endothermic process
because it
A. Requires heat to be transferred from system to
surroundings and has a negative ∆H.
B. Requires heat to be transferred from the
surroundings to system and has a positive ∆H.
C. Involves a decrease in entropy.
D. Involves a decrease in kinetic energy.
8.
How much heat in joules is required to melt 3
mol of ice? (The heat of fusion is +6.01 kJ/mol.)
A. 6.01 kJ
B. 18.03 kJ
C. –6.01 kJ
D. –18.03 kJ
thermo_rev_ws.doc
9.
Which of these phase changes does not involve the absorption of heat
energy?
A. Boiling
B. Condensation
C. Melting
D. Vaporization
10. When a material boils, energy is
A. Absorbed by the material.
B. Released by the material.
C. Absorbed by a catalyst.
D. Not exchanged.
11. When water evaporates, energy is
A. Not exchanged.
B. Transferred to a catalyst.
C. Absorbed by the water.
D. Released by the water vapor.
12. When steam condenses, energy is
A. Not exchanged.
B. Transferred to a catalyst.
C. Absorbed by the water.
D. Released by the water vapor.
13. The equation shows the change in enthalpy when 1 mol of liquid water
vaporizes into water vapor. This is called the molar heat of vaporization,
∆Hvap. Given this information, which is the proper value for the molar
heat of condensation, ∆Hcond? H2O (l)  H2O (g) ∆Hvap = +40.7 kJ
A. ∆Hcond = -40.7 kJ
B. ∆Hcond = 0 kJ
C. ∆Hcond = -571.6 kJ
D. ∆Hcond = +571.6 kJ
14. How much heat in joules does it take to raise 10 g of water from 25 °C to
35 °C? [The specific heat of water is 4.18 J/g·°C]
A. 41.8 J
B. 418 J
C. 4180 J
D. 41,800 J
15. How is the amount of heat needed to melt ice related to the amount of
heat needed to freeze the same amount of water?
A. The amount needed to melt ice is twice as high as the amount needed
to freeze water.
B. The amount needed to melt ice is three times as high as the amount
needed to freeze water.
C. The two amounts are the same but with the opposite sign (positive
versus negative).
D. The two values are not related to each other.
16. A student performed the following experiment. He drew and labeled the
graph below based on his results. Which best describes his results?
A. The reaction is endothermic.
B. The reaction is exothermic.