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Version A
Chapter 17 - Thermochemistry
Matching
Match each item with the correct statement below.
a. calorimeter
c. joule
b. specific heat
d. enthalpy
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1.
2.
3.
4.
quantity of heat needed to raise the temperature of 1 g of a substance by 1 C
SI unit of energy
device used to measure the heat absorbed or released during a chemical or physical process
potential energy of the products minus potential energy of the reactants
Multiple Choice
Identify the letter of the choice that best completes the statement or answers the question.
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5. A piece of metal is heated, then submerged in cool water. Which statement below describes what happens?
a. The temperature of the water will decrease and the temperature of the metal will increase.
b. The temperature of the water will increase and the temperature of the metal will stay the
same.
c. The temperature of the water will decrease and the temperature of the metal will stay the
same.
d. The temperature of the water will increase and the temperature of the metal will decrease.
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6. What would likely happen if you were to touch the flask in which an endothermic reaction were occurring?
a. The flask would probably feel cooler than before the reaction started.
b. The flask would probably feel warmer than before the reaction started.
c. The flask would feel the same as before the reaction started.
d. none of the above
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7. Which of the following is transferred due to a temperature difference?
a. chemical energy
c. electrical energy
b. potential energy
d. heat
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8. In an exothermic reaction, the energy stored in the chemical bonds of the reactants is ____.
a. equal to the energy stored in the bonds of the products
b. greater than the energy stored in the bonds of the products
c. less than the energy stored in the bonds of the products
d. less than the heat released
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9. A process that releases heat is a(n) ____.
a. endothermic process
b. polythermic process
c. exothermic process
d. isothermic process
____ 10. How many joules are in 148 calories? (1 cal = 4.18 J)
a. 6.61 J
c. 148 J
b. 35.4 J
d. 619 J
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____ 11. How can you describe the specific heat of olive oil if it takes approximately 420 J of heat to raise the temperature of
7 g of olive oil by 30 C?
a. greater than the specific heat of liquid
c. equal to the specific heat of liquid water
water
b. less than the specific heat of liquid water d. Not enough information is given.
____ 12. The specific heat of silver is 0.24
. How many joules of energy are needed to warm 4.37 g of silver from 25.0 C
to 27.5 C?
a. 2.62 J
b. 0.14 J
c. 45.5 J
d. 0.022 J
____ 13. What does the symbol H stand for?
a. the specific heat of a substance
b. the heat capacity of a substance
c. The enthalpy for a chemical reaction
d. one Calorie given off by a reaction
____ 14. During a phase change, the temperature of a substance ____.
a. increases
c. remains constant
b. decreases
d. may increase or decrease
____ 15. To calculate the amount of heat absorbed as a substance melts, which of the following information is needed?
a. the mass of the substance
c. the change in temperature
b. the specific heat of the substance
d. the density of the sample
____ 16. Heat usually flows:
a. From a warm object to a cool object.
b. From a cool object to a warm object.
____ 17. A reaction is exothermic if:
a. The products have more energy than the
reactants.
b. The products have the same amount of
energy as the reactants.
____ 18. H2O2  H2O + O2 + 256 kJ
This reaction above is:
a. Endothermic because it produces heat.
b. Exothermic because it produces heat.
c. Back and forth from a cool object and a
warm object.
d. None of the above.
c. H is positive.
d. H is negative.
c. Endothermic because it requires heat.
d. Exothermic because it requires heat.
____ 19. 2NaHCO3 + Energy  Na2CO3 + H2O + CO2
This reaction above is:
a. Endothermic because it produces heat.
c. Endothermic because it requires heat.
b. Exothermic because it produces heat.
d. Exothermic because it requires heat.
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____ 20. A 10 g sample of an unknown metal changed from 50.4oC to 25oC and released 114 J of heat. What is the substance?
a. Iron
c. Titanium
b. Lead
d. Aluminum
____ 21. A sample of granite (specific heat = 0.803 J/g*oC) was heated from 25oC to 40oC. In the process, it absorbed
5696 J of energy. Find the mass of the substance.
a. 155 g
b. 473 g
____ 22. Which is endothermic?
a. burning gasoline
b. ice freezing
c. 1.1 x 105 g
d. 9.4 x 10-6 g
c. baking a cake
d. lighting a candle
____ 23. If 335 g of water at 65.5oC loses 9750 J of heat, what is the final temperature of the water?
a. 72.5oC
c. -58.5oC
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b. 58.5 C
d. -72.5oC
____ 24. How much heat is required to vaporize 25.7 g of liquid water at 100oC?
a. 107 J
c. 8584 J
b. 58,082 J
d. 10,743 J
____ 25. H2O (s)  H2O (l)
This reaction above is:
a. Exothermic because it requires energy.
b. Endothermic because it requires energy.
c. Exothermic because it releases energy.
d. Endothermic because it releases energy.
____ 26. NH3 (g)  NH3 (l)
The reaction above is:
a. Exothermic because it absorbs heat.
b. Endothermic because it releases heat.
c. Exothermic because it releases heat.
d. Endothermic because it absorbs heat.
____ 27. How much energy is absorbed when 15 g of ice at -3oC changes to liquid water at 20oC?
a. 707 J
c. 6356 J
b. 1346 J
d. 35,246 J
____ 28. How much heat is released when 30 grams of water vapor at 114oC changes into liquid water?
a. 66, 952 J
c. 68,648 J
b. -66, 952 J
d. -68,648 J
____ 29. If a potential energy diagram (below) has the reactants listed as higher in energy than the products,
the reaction would be classified as:
a. Exothermic because it releases energy.
b. Endothermic because it releases energy.
c. Exothermic because it absorbs energy.
d. Endothermic because it absorbs energy.
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____ 30. What does the arrow in the diagram (below) refer to?
a. Activation Energy
b. Enthalpy
c. Potential Energy of the Reactants
d. Potential Energy of the Products
____ 31. What does the arrow in the diagram (below) refer to?
a. Activation Energy
b. Enthalpy
c. Potential Energy of the Reactants
d. Potential Energy of the Products
____ 32. In which of the following is entropy increasing?
a. H2O (l)  H2O (s)
c. 2H2 (g) + O2 (g) 2H2O (g)
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b. O2 gas at 30 C O2 gas at 25 C
d. H2O (l)  H2O (g)
____ 33. In which of the following is entropy decreasing?
a. CO2 (aq)  CO2 (g)
c. MgCl2 (s)  Mg2+ (aq) + 2Cl- (aq)
b. NaCl (l)  NaCl (s)
d. Entropy never decreases
34. If the pressure on the equilibrium system 2CO(g) + O2 (g)  2CO2 (g) is increased,
a. the quantity of CO(g) would increase.
c. the quantity of CO2 (g) would decrease.
b. the quantity of CO2 (g) would increase.
d. no quantities would change.
35. What is the effect on concentration if more CO (g) is added to the following equilibrium system:
2CO(g) + O2 (g)  2CO2 (g)
a. The concentration of CO2 increases
b. The concentration of O2 increases
c. the concentration of CO2 decreases
d. both the concentrations of CO2 and O2 remain the same
36. An increase in the concentration of products would
a. shift the reaction to the left
c. shift the reaction to the right
b. have no effect
d. increase the rate of the reaction
37. How does a catalyst speed up a reaction?
a. It makes the reaction endothermic.
b. It lowers the activation energy.
c. It makes the reaction exothermic.
d. It raises the activation energy.
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38. A measure of the disorder of a system is called what?
a. specific heat
c. calorimetry
b. entropy
d. enthalpy
Use the heating curve below to answer numbers 39 – 40.
39. What is happening between letters C and D?
a. A gas is evaporating
b. a gas is being heated
c. A solid is melting
d. A liquid is being heated
40. Which equation would you use to calculate the amount of heat required to go from D to E?
a. q = mC∆T
c. q = m∆Hfusion
b. q = m∆Hvaporization
d. That calculation cannot be done with one equation.
41. Which of the following explains both conditions that are favored in nature?
a. exothermic and disorder decreasing.
c. endothermic and disorder decreasing
b. endothermic and disorder increasing
d. exothermic and disorder increasing
42. All of the following would speed up a reaction EXCEPT which one?
a. decrease the surface area
c. stir it
b. add a catalyst
d. heat it
43. What does the collision theory say?
a. In order to react, two things must have the right amount of energy when they collide.
b. In order to react, two things must have the correct orientation when they collide.
c. Both A and B are correct.
d. Neither A nor B are correct.
44. What does it mean if a reaction is at “equilibrium”?
a. You have equal moles of reactants and products.
b. You have equal grams of reactants and products.
c. The rates of the forward and reverse reactions are equal.
d. You start with equal amounts of your two reactants.
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45. Which of the following shows the correct Keq expression for this reaction: 2A(aq) + 3B(aq)  C(aq) + 4D(aq)
a. [A][B]
c. [C][D]
[C][D]
[A][B]
b. [A]2[B]3
d. [C][D]4
[C][D]4
[A]2[B]3
46. What does it mean if Keq is greater than 1?
a. Equilibrium lies toward the products.
b. Equilibrium lies toward the reactants.
c. The grams of reactants equal the grams of products.
d. The moles or reactants equal the moles of products.
47. Which of the following should be included in the Keq equation?
a. (s) and (l), but not (aq) and (g)
b. (aq) and (g), but not (s) and (l)
c. only (s), (l), and (g)
d. only (aq)
48. Calculate Keq for the following reaction, given the information below:
Concentrations:
1.03 M of NH3;
0.102 M of N2;
a. Keq = 2.45
c. Keq = 0.41
b. Keq = 0.16
d. Keq = 6.23
3H2(g) + N2 (g)  2NH3 (g)
1.62 M of H2
49. What is the only thing that will affect Keq?
a. pressure
c. temperature
b. adding more products
d. adding more reactants
50. The average kinetic energy of particles describes which of these?
a. volume
b. pressure
c. temperature
d. mass