Chemistry and Chemical Reactivity 9th Edition By Kotz - Test Bank

Chemistry and Chemical Reactivity 9th Edition By Kotz – Test Bank

 

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Sample Questions Are Posted Below

 

MULTIPLE CHOICE

 

1. The energy stored in a fuel is called _____.

a.	heat
b.	internal energy
c.	temperature
d.	kinetic energy
e.	potential energy

 

 

ANS:  E

 

2. Which of the following statements is/are CORRECT?

	1.	A system is defined as an object or collection of objects being studied.
	2.	Surroundings are defined as the entire universe, including the system.
	3.	In an endothermic reaction, heat is transferred from the system to the surroundings.

 

a.

1 only

b.

2 only

c.

3 only

d.

1 and 3

e.

1, 2, and 3

 

 

ANS:  A

 

3. A hot piece of iron is dropped into a beaker containing colder water. Which of the following statements is/are CORRECT?

	1.	Energy is transferred as heat from the iron to the water.
	2.	Thermal equilibrium is attained when the iron and the water reach the same temperature.
	3.	Thermal energy from the iron is converted to electrostatic energy in the water.

 

a.

1 only

b.

2 only

c.

3 only

d.

1 and 2

e.

1, 2, and 3

 

 

ANS:  D

 

4. Which one of the following statements is INCORRECT?

a.	Energy is neither created nor destroyed in chemical reactions.
b.	Kinetic energy is the energy that results from an object’s position.
c.	Exothermic processes transfer heat from the system into the surroundings.
d.	Increasing the thermal energy of a gas increases the motion of its atoms.
e.	Energy is the capacity to do work.

 

 

ANS:  B

 

5. Many homes are heated using natural gas. The combustion of natural gas converts

a.	chemical potential energy to thermal energy.
b.	thermal energy to mechanical energy.
c.	mechanical energy to chemical potential.
d.	electrostatic energy to mechanical energy.
e.	gravitational energy to acoustic energy.

 

 

ANS:  A

 

 

6. Which of these physical changes would require the release of energy?

a.	condensing a gas
b.	boiling a liquid
c.	melting a solid
d.	all of these
e.	none of these

 

 

ANS:  A

 

7. Which of the following processes is/are endothermic?

	1.	the combustion of hydrogen
	2.	the condensation of water
	3.	the evaporation of isopropyl alcohol

 

a.

1 only

b.

2 only

c.

3 only

d.

1 and 3

e.

1, 2, and 3

 

 

ANS:  C

 

8. Which of the following processes is/are exothermic?

	1.	the reaction of butane with oxygen
	2.	the melting of gold
	3.	cooling copper from 225 °C to 65 °C

 

a.

1 only

b.

2 only

c.

3 only

d.

1 and 3

e.

1, 2, and 3

 

 

ANS:  D

 

9. Which of the following is an endothermic process?

a.	work is done by the system on the surroundings
b.	heat energy flows from the system to the surroundings
c.	work is done on the system by the surroundings
d.	heat energy is evolved by the system
e.	none of the above

 

 

ANS:  C

 

10. Specific heat capacity is

a.	the quantity of heat needed to change the temperature of 1.00 g of a substance by 1 K.
b.	the quantity of heat needed to change the temperature of 1.00 g of a substance by 4.184 K.
c.	the capacity of a substance to gain or lose a 1.00 J of energy in the form of heat.
d.	the temperature change undergone when 1.00 g of a substance absorbs 4.184 J.
e.	the maximum amount of energy in the form of heat that 1.00 g of a substance may absorb without decomposing.

 

 

ANS:  A

 

 

11. It is relatively easy to change the temperature of a substance that

a.	is very massive.
b.	is an insulator.
c.	has a high specific heat capacity.
d.	has a low specific heat capacity.
e.	is brittle.

 

 

ANS:  D

 

12. Heat capacity is defined as

a.	the amount of heat required to raise the temperature of 1 gram of substance by 1 K.
b.	the amount of heat required to raise the temperature of a substance by 1 K.
c.	the amount of heat required to vaporize a solid or liquid.
d.	the maximum amount of heat that a substance may absorb without decomposing.
e.	4.18 cal/g×K.

 

 

ANS:  B

 

13. The specific heat capacity of copper is 0.384 J/g×°C.  What is the molar specific heat capacity of this substance?  The molar mass of copper is 63.54 g/mol.

a.	24.4 J/mol×°C
b.	0.00604 J/mol×°C
c.	165 J/mol×°C
d.	0.384 J/mol×°C
e.	2.60 J/mol×°C

 

 

ANS:  A

 

14. Which of the following statements is/are CORRECT?

	1.	Specific heat capacity is a positive value for liquids and solids and a negative value for gases.
	2.	The larger the heat capacity of an object, the more thermal energy it can store.
	3.	When heat is transferred from the surroundings to the system, q is negative.

 

a.

1 only

b.

2 only

c.

3 only

d.

1 and 2

e.

1, 2, and 3

 

 

ANS:  B

 

15. Exactly 212.2 J will raise the temperature of 10.0 g of a metal from 25.0 °C to 60.0 °C. What is the specific heat capacity of the metal?

a.	0.606 J/(g·°C)
b.	1.65 J/(g·°C)
c.	14.5 J/(g·°C)
d.	50.8 J/(g·°C)
e.	none of these

 

 

ANS:  A

 

 

16. A 100 g sample of each of the following metals is heated from 35°C to 45°C.  Which metal absorbs the greatest amount of heat energy?

Metal	Specific Heat Capacity
copper	0.385 J/(g·°C)
magnesium	1.02 J/(g·°C)
mercury	0.138 J/(g·°C)
silver	0.237 J/(g·°C)
lead	0.129 J/(g·°C)

 

a.

magnesium

b.

lead

c.

mercury

d.

silver

e.

copper

 

 

ANS:  A

 

 

17. If 50.0 g of benzene, C₆H₆, at 25.0 °C absorbs 2.71 kJ of energy in the form of heat, what is the final temperature of the benzene? The specific heat capacity of benzene is 1.72 J/g×K.

a.

25.0 °C

b.

31.5 °C

c.

56.5 °C

d.

32.3 °C

e.

57.3 °C

 

 

ANS:  C

 

18. How much energy is gained by nickel when 18.7 g of nickel is warmed from 20.5 °C to 79.8 °C?  The specific heat capacity of nickel is 0.443 J/(g·°C).

a.

1.70 ´ 102 J

b.

35.35 J

c.

26.27 J

d.

4.91 ´ 102 J

e.

6.61 ´ 102 J

 

 

ANS:  D

 

19. If 35.0 g H₂O at 22.7 °C is combined with 65.0 g H₂O at 87.5 °C, what is the final temperature of the mixture? The specific heat capacity of water is 4.184 J/g×K.

a.

25.1 °C

b.

45.4 °C

c.

50.8 °C

d.

64.8 °C

e.

48.9 °C

 

 

ANS:  D

 

20. A 170.0-g sample of metal at 79.00°C is added to 170.0 g of H₂O(l) at 14.00°C in an insulated container.  The temperature rises to 16.19°C.  Neglecting the heat capacity of the container, what is the specific heat capacity of the metal?  The specific heat capacity of H₂O(l) is 4.18 J/(g·°C).

a.	4.18 J/(g·°C)
b.	120 J/(g·°C)
c.	0.146 J/(g·°C)
d.	–0.146 J/(g·°C)
e.	28.6 J/(g·°C)

 

 

ANS:  C

 

21. If 46.1 g Cu at 11.6 °C is placed in 85.0 g H₂O at 72.4 °C, what is the final temperature of the mixture? The specific heat capacities of copper and water are 0.385 J/g×K and 4.184 J/g×K, respectively.

a.

71.2 °C

b.

63.6 °C

c.

51.0 °C

d.

42.0 °C

e.

69.5 °C

 

 

ANS:  E

 

 

22. Which of the following processes will result in the lowest final temperature of the metal–water mixture at when thermal equilibrium is reached?  The specific heat capacity of nickel is 0.443 J/(g·°C). The specific heat capacity of water is 4.184 J/(g·°C).

a.	the addition of 100 g of nickel at 95°C to 80 mL of water at 25°C in an insulated container
b.	the addition of 100 g of nickel at 95°C to 100 mL of water at 25°C in an insulated container
c.	the addition of 100 g of nickel at 95°C to 40 mL of water at 25°C in an insulated container
d.	the addition of 100 g of nickel at 95°C to 20 mL of water at 25°C in an insulated container
e.	the addition of 100 g of nickel at 95°C to 60 mL of water at 25°C in an insulated container

 

 

ANS:  B

 

23. When 66.0 g of an unknown metal at 28.5 °C is placed in 83.0 g H₂O at 78.5 °C, the water temperature decreases to 75.9 °C. What is the specific heat capacity of the metal? The specific heat capacity of water is 4.184 J/g×K.

a.	0.055 J/g×K
b.	0.29 J/g×K
c.	0.69 J/g×K
d.	0.18 J/g×K
e.	2.6 J/g×K

 

 

ANS:  B

 

24. A 41.3-g piece of nickel (s = 0.443 J/(g·°C)), initially at 255.8°C, is added to 144.8 g of a liquid, initially at 23.1°C, in an insulated container.  The final temperature of the metal–liquid mixture at equilibrium is 35.4°C.  What is the identity of the liquid?  Neglect the heat capacity of the container.

a.	acetone (s = 2.15 J/(g·°C))
b.	hexane (s = 2.27 J/(g·°C))
c.	water (s = 4.18 J/(g·°C))
d.	methanol (s = 2.53 J/(g·°C))
e.	ethanol (s = 2.43 J/(g·°C))

 

 

ANS:  B

 

25. How much energy is needed to convert 57.5 grams of ice at 0.00°C to liquid water at 75.0°C?

specific heat capacity (ice) = 2.10 J/g°C

specific heat capacity (liquid water) = 4.18 J/g°C

heat of fusion = 333 J/g

heat of vaporization = 2258 J/g

a.

18.0 kJ

b.

2.06 kJ

c.

28.2 kJ

d.

37.2 kJ

e.

148 kJ

 

 

ANS:  D

 

26. Calculate the energy in the form of heat (in kJ) required to convert 325 grams of liquid water at 20.0 °C to steam at 115 °C. Assume that no energy in the form of heat is transferred to the environment. (Heat of fusion = 333 J/g; heat of vaporization = 2256 J/g; specific heat capacities: liquid water = 4.184 J/g×K, steam = 1.92 J/g×K)

a.

129 kJ

b.

121 kJ

c.

851 kJ

d.

914 kJ

e.

735 kJ

 

 

ANS:  C

 

27. Calculate the energy in the form of heat (in kJ) required to change 71.8 g of liquid water at 25.7 °C to ice at –16.1 °C. Assume that no energy in the form of heat is transferred to the environment. (Heat of fusion = 333 J/g; heat of vaporization = 2256 J/g; specific heat capacities: ice = 2.06 J/g×K, liquid water = 4.184 J/g×K)

a.

–12.6 kJ

b.

–7.7 kJ

c.

–34.0kJ

d.

–31.6 kJ

e.

–10.1 kJ

 

 

ANS:  C

 

 

28. 44.0 g of ice at –20.0 °C is mixed with 325 g of water at 32.1 °C. Calculate the final temperature of the mixture. Assume that no energy in the form of heat is transferred to the environment. (Heat of fusion = 333 J/g; specific heat capacities: ice = 2.06 J/g×K, liquid water = 4.184 J/g×K)

a.

–0.6 °C

b.

5.5 °C

c.

12.1 °C

d.

17.6 °C

e.

38.9 °C

 

 

ANS:  D

 

29. What is the minimum mass of ice at 0.0 °C that must be added to 1.00 kg of water to cool the water from 28.0 °C to 12.0 °C? (Heat of fusion = 333 J/g; specific heat capacities: ice = 2.06 J/g×K, liquid water = 4.184 J/g×K)

a.

175 g

b.

201 g

c.

244 g

d.

299 g

e.

1140 g

 

 

ANS:  A

 

30. The heat of vaporization of benzene, C₆H₆, is 30.7 kJ/mol at its boiling point of 80.1 °C. How much energy in the form of heat is required to vaporize 102 g benzene at its boiling point?

a.	0.302 kJ
b.	23.6 kJ
c.	24.2 kJ
d.	40.1 kJ
e.	3.14 ´ 103 kJ

 

 

ANS:  D

 

31. One statement of the first law of thermodynamics is that

a.	the amount of work done on a system is dependent of the pathway.
b.	the total work done on a system must equal the heat absorbed by the system.
c.	the total work done on a system is equal in magnitude, but opposite in sign of the heat absorbed by the system.
d.	the total energy change for a system is equal to the sum of the heat transferred to or from the system and the work done by or on the system.
e.	in any chemical process the heat flow must equal the change in enthalpy.

 

 

ANS:  D

 

32. Which of the following statements is/are CORRECT?

	1.	If a reaction occurs at constant pressure, q = DH.
	2.	The change in energy for a system is defined as the sum of the energies transferred as heat and work (i.e., DU = q + w).
	3.	If a reaction occurs at constant volume, q = w

 

a.

1 only

b.

2 only

c.

3 only

d.

1 and 2

e.

1, 2, and 3

 

 

ANS:  D

 

33. Which of the following thermodynamic quantities are state functions: heat (q), work (w), enthalpy change (DH), and/or internal energy change (DU)?

a.

q only

b.

w only

c.

DH only

d.

DU only

e.

DH and DU

 

 

ANS:  E

 

34. Calculate DU of a gas for a process in which the gas absorbs 19 J of heat and does 49 J of work by expanding.

a.	30 J
b.	68 J
c.	–68 J
d.	0, because DU is a state function
e.	–30 J

 

 

ANS:  E

 

35. What is the change in internal energy of the system (DU) if 7 kJ of heat energy is evolved by the system and 99 kJ of work is done on the system for a certain process?

a.

92 kJ

b.

–106 kJ

c.

–7 kJ

d.

–92 kJ

e.

106 kJ

 

 

ANS:  A

 

 

36. If q = 98 kJ and w = 4 kJ for a certain process, that process

a.	requires a catalyst.
b.	is endothermic.
c.	occurs slowly.
d.	is exothermic.
e.	cannot occur.

 

 

ANS:  B

 

37. Given the thermochemical equation

AlCl₃(s) + O₂(g)    ® 2Al₂O₃(s) + 6Cl₂(g); D_rHº = –529 kJ/mol-rxn

find D_rHº for the following reaction.

Al₂O₃(s) +  Cl₂(g) ® AlCl₃(s) + O₂(g)

a.	+88.2 kJ/mol-rxn
b.	+264.5 kJ/mol-rxn
c.	+529.0 kJ/mol-rxn
d.	+176.3 kJ/mol-rxn
e.	-176.3 kJ/mol-rxn

 

 

ANS:  A

 

 

38. The thermochemical equation for the combustion of methanol is shown below.

CH3OH() + 3/2 O2(g) ® CO2(g) + 2 H 2O(g)

DrH° = –638.7 kJ/mol-rxn

What is the enthalpy change for the combustion of 8.59 g CH₃OH?

a.	–171 kJ
b.	–19.9 kJ
c.	–2.38 ´ 103 kJ
d.	–5.49 ´ 103 kJ
e.	–1.76 ´ 106 kJ

 

 

ANS:  A

 

39. The thermochemical equation for the combustion of butane is shown below.

C4H10(g) + 13/2 O2(g) ® 4 CO2(g) + 5 H2O()

DrH° = –2877 kJ/mol-rxn

What is the enthalpy change for the following reaction?

8 CO₂(g) + 10 H₂O() ® 2 C₄H₁₀(g) + 13 O₂(g)

a.	+1439 kJ/mol-rxn
b.	+2877 kJ/mol-rxn
c.	–5754 kJ/mol-rxn
d.	–2877 kJ/mol-rxn
e.	+5754 kJ/mol-rxn

 

 

ANS:  E

 

40. At constant pressure and 25°C, what is D_rH° for the following reaction

2C₂H₆(g) + 7O₂(g) ® 4CO₂(g) + H₂O(l)

if the complete consumption of 89.4 g of C₂H₆ liberates –4638 kJ of heat energy?

a.	–3120 kJ/mol-rxn
b.	–1560 kJ/mol-rxn
c.	–27600 kJ/mol-rxn
d.	–13800 kJ/mol-rxn
e.	–787 kJ/mol-rxn

 

 

ANS:  A

 

41. What quantity, in moles, of oxygen is consumed when 369.3 kJ of energy is evolved from the combustion of a mixture of H₂(g) and O₂(g)?

H₂(g) + O₂(g)  ®  H₂O(l); D_rH° = –285.8 kJ/mol-rxn

a.

0.6461 mol

b.

1.292 mol

c.

0.3869 mol

d.

1.146 mol

e.

0.1461 mol

 

 

ANS:  A

 

 

42. Iron oxide reacts with aluminum in an exothermic reaction.

Fe₂O₃(s) + 2 Al(s) ® 2 Fe(s) + Al₂O₃(s)

The reaction of 5.00 g Fe₂O₃ with excess Al(s) evolves 26.6 kJ of energy in the form of heat. Calculate the enthalpy change per mole of Fe₂O₃ reacted.

a.	–5.32 kJ/mol
b.	–1.33 ´ 102 kJ/mol
c.	–2.12 ´ 104 kJ/mol
d.	–2.12 ´ 102 kJ/mol
e.	–8.50 ´ 102 kJ/mol

 

 

ANS:  E

 

43. How much heat is liberated at constant pressure if 0.834 g of calcium carbonate reacts with 48.9 mL of 0.668 M hydrochloric acid?

CaCO₃(s) + 2HCl(aq)  ®  CaCl₂(aq) + H₂O(l) + CO₂(g); D_rH° = –15.2 kJ/mol-rxn

a.

–0.127 kJ

b.

–0.375 kJ

c.

–12.7 kJ

d.

–0.248 kJ

e.

–10.2 kJ

 

 

ANS:  A

 

 

44. Hydrazine, N₂H₄, is a liquid used as a rocket fuel. It reacts with oxygen to yield nitrogen gas and water.

N₂H₄() + O₂(g) ® N₂(g) + 2 H₂O()

The reaction of 6.50 g N₂H₄ evolves 126.2 kJ of heat. Calculate the enthalpy change per mole of hydrazine combusted.

a.	–19.4 kJ/mol
b.	–25.6 kJ/mol
c.	–126 kJ/mol
d.	–622 kJ/mol
e.	–820. kJ/mol

 

 

ANS:  D

 

45. CaO(s) reacts with water to form Ca(OH)₂(aq). If 6.50 g CaO is combined with 99.70 g H₂O in a coffee cup calorimeter, the temperature of the resulting solution increases from 21.7 °C to 43.1 °C. Calculate the enthalpy change for the reaction per mole of CaO. Assume that the specific heat capacity of the solution is 4.18 J/g×K.

a.	–1.45 kJ/mol
b.	–82.0 kJ/mol
c.	–9.42 kJ/mol
d.	–165 kJ/mol
e.	–532 kJ/mol

 

 

ANS:  B

 

 

46. Commercial cold packs consist of solid ammonium nitrate and water. NH₄NO₃ absorbs 25.69 kJ of heat per mole dissolved in water. In a coffee-cup calorimeter, 5.60 g NH₄NO₃ is dissolved in 100.0 g of water at 22.0 °C. What is the final temperature of the solution? Assume that the solution has a specific heat capacity of 4.18 J/g×K.

a.	0.0 °C
b.	17.9 °C
c.	11.6 °C
d.	–54.8 °C
e.	26.1 °C

 

 

ANS:  B

 

47. When 10.0 g KOH is dissolved in 100.0 g of water in a coffee-cup calorimeter, the temperature rises from 25.18 °C to 47.53 °C. What is the enthalpy change per gram of KOH dissolved in the water? Assume that the solution has a specific heat capacity of 4.18 J/g×K.

a.	–116 J/g
b.	–934 J/g
c.	–1.03 ´ 103 J/g
d.	–2.19 ´ 103 J/g
e.	–1.03 ´ 104 J/g

 

 

ANS:  C

 

48. When 50.0 mL of 1.30 M of HCl(aq) is combined with 50.0 mL of 1.20 M of NaOH(aq) in a coffee-cup calorimeter, the temperature of the solution increases by 8.01°C. What is the change in enthalpy for this balanced reaction?

HCl(aq) + NaOH(aq)  ®  NaCl(aq) + H₂O(l)

Assume that the solution density is 1.00 g/mL and the specific heat capacity of the solution is 4.18 J/g×°C.

 

a.

–55.8 kJ

b.

55.8 kJ

c.

51.5 kJ

d.

–51.5 kJ

e.

–26.8 kJ

 

 

ANS:  A

 

 

49. When 0.236 mol of a weak base (A^–) is reacted with excess HCl, 6.91 kJ of energy is released as heat. What is DH for this reaction per mole of A^– consumed?

a.	–34.2 kJ/mol
b.	–59.4 kJ/mol
c.	–29.3 kJ/mol
d.	34.2 kJ/mol
e.	29.3 kJ/mol

 

 

ANS:  C

 

 

 

50. A chemical reaction in a bomb calorimeter evolves 3.86 kJ of energy in the form of heat. If the temperature of the bomb calorimeter increases by 4.17 K, what is the heat capacity of the calorimeter?

a.	3.87 ´ 103 J/K
b.	311 J/K
c.	926 J/K
d.	1.8 ´ 103 J/K
e.	1.61 ´ 104 J/K

 

 

ANS:  C

 

51. A bomb calorimeter has a heat capacity of 2.47 kJ/K. When a 0.105-g sample of a certain hydrocarbon was burned in this calorimeter, the temperature increased by 2.14 K. Calculate the energy of combustion for 1 g of the hydrocarbon.

a.	–5.29 J/g
b.	J/g
c.	–0.120 J/g
d.	J/g
e.	–0.560 J/g

 

 

ANS:  B

 

 

52. A bomb calorimeter has a heat capacity of 2.47 kJ/K. When a 0.123-g sample of ethylene (C₂H₄) was burned in this calorimeter, the temperature increased by 2.50 K. Calculate the enthalpy change per mole of ethylene combusted.

a.	–5.29 kJ/mol
b.	–50.2 kJ/mol
c.	–563 kJ/mol
d.	–0.304 kJ/mol
e.	–1.41 ´ 103 kJ/mol

 

 

ANS:  E

 

 

53. Combustion of 7.21 g of liquid benzene (C₆H₆) causes a temperature rise of 50.3°C in a constant-pressure calorimeter that has a heat capacity of 5.99 kJ/°C.  What is DH for the following reaction?

C₆H₆(l) + O₂(g)  ®  6CO₂(g) + 3H₂O(l)

a.	–302 kJ/mol-rxn
b.	41.8 kJ/mol-rxn
c.	–41.8 kJ/mol-rxn
d.	–3.27 ´ 103 kJ/mol-rxn
e.	302 kJ/mol-rxn

 

 

ANS:  D

 

 

 

54. Acetylene, C₂H₂, is a gas used in welding. The molar enthalpy of combustion for acetylene is –2599 kJ. A mass of 0.338 g C₂H₂(g) is combusted in a bomb calorimeter. If the heat capacity of the calorimeter is 729 J/K and it contains 1.150 kg of water, what is the temperature increase of the bomb calorimeter? The specific heat capacity of water is 4.184 J/g×K and the molar mass of acetylene is 26.04 g/mol.

a.

1.59 K

b.

6.09 K

c.

7.01 K

d.

12.3 K

e.

18.0 K

 

 

ANS:  B

 

55. The overall chemical equation resulting from the sum of the following three steps is

 

2C(s) + 2H₂O(g) ® 2CO(g) + 2H₂(g)

CO(g) + H₂O(g) ® CO₂(g) + H₂(g)

CO(g) + 3H₂(g) ® CH₄(g) + H₂O(g)

 

a.	2C(s) + 2H2O(g) ® CO2(g) + CH4(g)
b.	2C(s) + 3H2O(g) ® CO(g) + CO2(g) + 3H2(g)
c.	2C(s) + H2O(g) + H2(g)® CO(g) + CH4(g)
d.	2CO(g) + 2H2(g) ® CH4(g) + CO2(g)
e.	2C(s) + CH4(g) + 3H2O(g) ® 3CO(g) + 5H2(g)

 

 

ANS:  A

 

56. Determine the heat of evaporation of carbon disulfide,

CS₂() ® CS₂(g)

given the enthalpies of reaction below.

	C(s) + 2 S(s) ® CS2()	DrH° = +89.4 kJ/mol-rxn
	C(s) + 2 S(s) ® CS2(g)	DrH° = +116.7 kJ/mol-rxn

 

a.	–206.1 kJ
b.	–27.3 kJ
c.	+27.3 kJ
d.	+206.1 kJ
e.	+1.31 kJ

 

 

ANS:  C

 

57. Which of the following has a standard enthalpy of formation value of zero at 25°C?

a.

I(g)

b.

I2(l)

c.

I2(s)

d.

I(s)

e.

I2(g)

 

 

ANS:  C

 

 

 

58. Determine the standard enthalpy of formation of Fe₂O₃(s) given the thermochemical equations below.

	Fe(s) + 3 H2O() ® Fe(OH)3(s) + 3/2 H2(g)	DrH° = +160.9 kJ/mol-rxn
	H2(g) + 1/2 O2(g) ® H2O()	DrH° = –285.8 kJ/mol-rxn
	Fe2O3(s) + 3 H2O() ® 2 Fe(OH)3(s)	DrH° = +288.6 kJ/mol-rxn

 

a.	–252.6 kJ/mol-rxn
b.	+163.7 kJ/mol-rxn
c.	–824.2 kJ/mol-rxn
d.	+33.2 kJ/mol-rxn
e.	+ 890.6 kJ/mol-rxn

 

 

ANS:  C

 

59. Using the following thermochemical data:

2Ho(s) + 6HF(g) ® 2HoF3(s) + 3H2(g)	DrH° = –1787.4 kJ/mol-rxn
2Ho(s) + 6HCl(g) ® 2HoCl3(s) + 3H2(g)	DrH° = –1457.0 kJ/mol-rxn

calculate D_rH° for the following reaction:

HoF₃(s) + 3HCl(g) ® HoCl₃(s) + 3HF(g)

a.	–3244.4 kJ/mol-rxn
b.	330.4 kJ/mol-rxn
c.	165.2 kJ/mol-rxn
d.	660.8 kJ/mol-rxn
e.	–1622.2 kJ/mol-rxn

 

 

ANS:  C

 

 

60. Determine the enthalpy change for the decomposition of calcium carbonate

CaCO₃(s) ® CaO(s) + CO₂(g)

given the thermochemical equations below.

	Ca(OH)2(s) ® CaO(s) + H2O()	DrH° = 65.2 kJ/mol-rxn
	Ca(OH)2(s) + CO2(g) ® CaCO3(s) + H2O()	DrH° = -113.8 kJ/mol-rxn
	C(s) + O2(g) ® CO2(g)	DrH° = -393.5 kJ/mol-rxn
	2 Ca(s) + O2(g) ® 2 CaO(s)	DrH° = -1270.2 kJ/mol-rxn

 

a.	+48.6 kJ/mol-rxn
b.	+179.0 kJ/mol-rxn
c.	+345.5 kJ/mol-rxn
d.	+441.0 kJ/mol-rxn
e.	+1711.7 kJ/mol-rxn

 

 

ANS:  B

 

 

61. Determine D_rH° for the following reaction,

2 NH₃(g) + 5/2 O₂(g) ® 2 NO(g) + 3 H₂O(g)

given the thermochemical equations below.

	N2(g) + O2(g) ® 2 NO(g)	DrH° = +180.8 kJ/mol-rxn
	N2(g) + 3 H2(g) ® 2 NH3(g)	DrH° = –91.8 kJ/mol-rxn
	2 H2(g) + O2(g) ® 2 H2O(g)	DrH° = –483.6 kJ/mol-rxn

 

a.	–1178.2 kJ/mol-rxn
b.	–452.8 kJ/mol-rxn
c.	–394.6 kJ/mol-rxn
d.	–211.0 kJ/mol-rxn
e.	+1178.2 kJ/mol-rxn

 

 

ANS:  B

 

62. Determine the standard enthalpy of formation of calcium carbonate from the thermochemical equations given below.

	Ca(OH)2(s) ® CaO(s) + H2O()	DrH° = 65.2 kJ/mol-rxn
	Ca(OH)2(s) + CO2(g) ® CaCO3(s) + H2O()	DrH° = -113.8 kJ/mol-rxn
	C(s) + O2(g) ® CO2(g)	DrH° = -393.5 kJ/mol-rxn
	2 Ca(s) + O2(g) ® 2 CaO(s)	DrH° = -1270.2 kJ/mol-rxn

 

a.	-1712.3 kJ/mol-rxn
b.	-441.8 kJ/mol-rxn
c.	-849.6 kJ/mol-rxn
d.	-980.6 kJ/mol-rxn
e.	-1207.6 kJ/mol-rxn

 

 

ANS:  E

 

63. Which of the following reactions corresponds to the thermochemical equation for the standard molar enthalpy of formation of solid calcium nitrate?

a.	Ca2+(aq) + 2NO3–(aq) ® Ca(NO3)2(s)
b.	Ca(OH)2(s) + 2HNO3(aq) ® Ca(NO3)2(s) + 2H2O()
c.	Ca(s) + N2(g) + 3O2(g) ® Ca(NO3)2(s)
d.	Ca(s) + 2HNO3(aq) ® Ca(NO3)2(s) + H2(g)
e.	Ca(s) + 2N(g) + 6O(g) ® Ca(NO3)2(s)

 

 

ANS:  C

 

 

64. Which of the following chemical equations does not correspond to a standard molar enthalpy of formation?

a.	Mg(s) + C(s) + 3/2 O2(g) ® MgCO3(s)
b.	C(s) + 1/2 O2(g) ® CO(g)
c.	N2(g) + O2(g) ® 2 NO(g)
d.	N2(g) + 2 O2(g) ® N2O4(g)
e.	H2(g) + 1/2 O2(g) ® H2O()

 

 

ANS:  C

 

 

65. What is the standard enthalpy of formation of BaCO₃(s)?

BaO(s) + CO₂(g)  ®  BaCO₃(s); DH° = –269.3 kJ/mol-rxn

Substance	DfH°(kJ/mol-rxn)
BaO(s)	–553.5
CO2(g)	–393.5

 

a.	–109.3 kJ/mol-rxn
b.	–429.3 kJ/mol-rxn
c.	–677.7 kJ/mol-rxn
d.	–1216.3 kJ/mol-rxn
e.	677.7 kJ/mol-rxn

 

 

ANS:  D

 

 

66. Calculate D_rH° for the combustion of ammonia,

4 NH₃(g) + 7 O₂(g) ® 4 NO₂(g) + 6 H₂O()

using standard molar enthalpies of formation.

 

	molecule	DfH° (kJ/mol-rxn)
	NH3(g)	–45.9
	NO2(g)	+33.1
	H2O()	–285.8

 

a.	+30.24 kJ/mol-rxn
b.	–206.9 kJ/mol-rxn
c.	–298.6 kJ/mol-rxn
d.	–1398.8 kJ/mol-rxn
e.	–1663.6 kJ/mol-rxn

 

 

ANS:  D

 

67. What is D_rH° for the following phase change?

NaF(s) ® NaF(l)

Substance	DH°f (kJ/mol-rxn)
NaF(s)	–575.38
NaF(l)	–546.20

 

a.	1121.58 kJ/mol-rxn
b.	29.18 kJ/mol-rxn
c.	–1121.58 kJ/mol-rxn
d.	–29.18 kJ/mol-rxn
e.	0 kJ/mol-rxn

 

 

ANS:  B

 

 

 

68. The standard enthalpy change for the combustion of 1 mole of propane is –2043.0 kJ.

C₃H₈(g) + 5 O₂(g) ® 3 CO₂(g) + 4 H₂O(g)

Calculate D_fH° for propane based on the following standard molar enthalpies of formation.

 

	molecule	DfH° (kJ/mol-rxn)
	CO2(g)	–393.5
	H2O(g)	–241.8

 

a.	–1407.7 kJ/mol-rxn
b.	+104.7 kJ/mol-rxn
c.	–104.7 kJ/mol-rxn
d.	–4190.7 kJ/mol-rxn
e.	+1407.7 kJ/mol-rxn

 

 

ANS:  C

 

69. The standard molar enthalpy of formation of NH₃(g) is –45.9 kJ/mol. What is the enthalpy change if 9.51 g N₂(g) and 1.96 g H₂(g) react to produce NH₃(g)?

a.	–10.3 kJ/mol-rxn
b.	–20.7 kJ/mol-rxn
c.	–29.8 kJ/mol-rxn
d.	–43.7 kJ/mol-rxn
e.	–65.6 kJ/mol-rxn

 

 

ANS:  C

 

70. When 1 mole of Fe₂O₃(s) reacts with H₂(g) to form Fe(s) and H₂O(g) according to the following equation, 98.8 kJ of energy are absorbed.

Fe₂O₃(s) + 3 H₂(g)  ®  2 Fe(s) + 3 H₂O(g)

(A)		(B)

Is the reaction endothermic or exothermic, and which of the enthalpy diagrams above

represents this reaction?

a.	endothermic, A	c.	exothermic, A
b.	endothermic, B	d.	exothermic, B

 

 

ANS:  B

 

SHORT ANSWER

 

71. In thermodynamics, a(n) ________ is defined as the object, or collection of objects, being studied. The surroundings include everything else.

 

ANS:  system

 

 

72. The heat required to convert a solid at its melting point to a liquid is called the heat of ________.

 

ANS:  fusion

 

 

73. Dry ice converts directly from a solid to a gas when heated. This process is called ________.

 

ANS:  sublimation

 

 

74. Why are you at greater risk from being burned by steam at 100 °C than from liquid water at the same temperature?

 

ANS:  At 100 °C, steam has approximately 40 kJ/mole more potential energy than liquid water at the same temperature.

 

75. Internal energy and enthalpy are state functions. What is meant by this statement?

 

ANS:  In any process, the change in internal energy or the change in enthalpy is independent of the path between the two states. These values depend only on the initial and final states.