Chemistry Chapter 7 Temperatures of two bodies are equal when the

General Chemistry, 11e (Petrucci)

Chapter 7 Thermochemistry

1) A closed system can exchange matter but not energy with the surroundings.

2) Kinetic energy is the energy of motion.

3) Heat is usually transferred from a cold object to a hot object.

4) A system that absorbs heat is an exothermic system.

5) An expansion of gas by a system means that the system does work.

6) An expansion of gas by a system means that the internal energy of the system increases.

7) The maximum amount of work is provided by a reversible process because equilibrium between the

system and the surroundings is always maintained.

8) The enthalpy of a system is the internal energy minus the pressure-volume product.

9) Enthalpy is an extensive property.

10) The standard enthalpy for diamond and graphite are the same value.

11) Although CO is not toxic, there is concern that it causes global warming.

12) Choose the INCORRECT statement.

A) Kinetic energy is the energy of motion.

B) Potential energy is energy in action.

C) Heat is energy transferred as a result of a temperature difference.

D) Pressure-volume work is calculated by w = −PΔV.

E) Heat is transferred from a warmer body to a colder one.

13) Choose the INCORRECT statement.

A) The surroundings are the part of the universe that is studied.

B) Thermal energy is energy associated with random molecular motion.

C) Chemical energy is associated with chemical bonds and intermolecular forces.

D) Energy is the capacity to do work.

E) Work is done when a force acts through a distance.

14) Choose the INCORRECT statement.

A) Temperatures of two bodies are equal when the average kinetic energies of the two bodies become the

same.

B) The heat capacity is the quantity of heat required to change the temperature of the system by one

degree.

C) The specific heat is the heat capacity for one mole of substance.

D) The law of conservation of energy can be written: qsystem + qsurroundings = 0.

E) Most metals have low specific heats, as metals can be heated quickly.

15) When power was turned off to a 30.0 gal. water heater, the temperature of the water dropped from

75.0 °C to 22.5 °C. How much heat was lost to the surroundings?

A) -2.49 × 103 kJ

B) -2.49 × 107 kJ

C) -2.49 × 104 kJ

D) -2.49 × 1010 kJ

E) -2.49 kJ

16) 14.0 g of metal at 24.0 °C has 250 joules of heat added to it. The metal’s specific heat is 0.105 J/g °C.

What is its final temperature?

A) (250)(14.0)/0.105 °C

B) [250/(14.0)(0.105)] °C

C) [250 /(14.0)(0.105)] + 24.0 °C

D) (14.0)(0.105)/250 °C

E) (14.0)(0.105)(250) °C

17) 1219 joules of heat raise the temperature of 250 g of metal by 64 °C. What is the specific heat of the

metal in J/(g °C?)

A) (1219)(250)(64) J/(g °C)

B) (64)(250/1219) J/(g °C)

C) (1219)(64/250) J/(g °C)

D) (1219)(250/64) J/(g °C)

E) (1219)/(250 × 64) J/(g °C)

18) Lead, water, sulfur and arsenic have specific heats of 0.128, 4.18, 0.706, and 0.329 J g-1 °C-1,

respectively. Which of the following would need the smallest quantity of heat to change the temperature

of 5 g by 10 °C?

A) lead

B) water

C) sulfur

D) arsenic

19) What is the final temperature in the bomb calorimeter if 1.785 grams of benzoic acid (C6H5COOH) is

combusted in a calorimeter with a heat capacity of 5.02 kJ/ °C and initial temperature of 24.62 °C? The

heat of combustion of benzoic acid is -26.42 kJ/g.

A) 51.0 °C

B) 29.8 °C

C) 31.2 °C

D) 15.5 °C

E) 34.0 °C

20) The complete combustion of 1 mole of nitrobenzene, C6H5NO2, in a bomb calorimeter liberates 3088

kJ of heat and increases the temperature of the calorimeter assembly by 140.0 °C. What is the heat

capacity of this bomb calorimeter?

A) 1.25 kJ/ °C

B) 4.53 kJ/ °C

C) 22.1 kJ/ °C

D) 432 kJ/ °C

E) 43.1 kJ/ °C

21) The combustion of 90.0 g of oxalic acid, C2H2O4(s) in a bomb calorimeter whose heat capacity is 4.60

kJ/ °C causes the temperature to rise from 25.0 °C to 79.6 °C. What is the heat of combustion of oxalic

acid?

A) -21.2 kJ/mol

B) -54.6 kJ/mol

C) -126 kJ/mol

D) -211 kJ/mol

E) -251 kJ/mol

22) What is the work done in joules by the system when H2 expands against a constant pressure of 75 atm

at 45.3 °C? The change in volume is 24.0 L.

A) 1.8 × 103 J

B) -8.2 × 104 J

C) 8.2 × 104 J

D) 1.8 × 105 J

E) -1.8 × 105 J

23) Oxygen gas at 34.5 °C expands from 34.5 L to 45.7 L against a constant pressure of 750 mmHg. What

is the work done in joules by the system?

A) 1.12 × 103 J

B) -1.12 × 103 J

C) 9.09 × 104 J

D) -9.09 × 104 J

E) 4.55 × 103 J

24) Two solutions, 50.0 mL of 1.00 M BaCl2(aq) and 50.0 mL of 1.00 M Na2SO4(aq), both initially at 21.5

°C, are added to a calorimeter with a total heat capacity, after the solutions are added, of 1.10 kJ/ °C and

the temperature rises to 22.7 °C. Determine qrxn per mole of BaSO4(s) formed in the reaction.

A) -26.4 kJ/mol

B) +26.4 kJ/mol

C) -2.64 kJ/mol

D) +2.64 kJ/mol

25) Oxygen gas at 34.5 °C is compressed from 45.7 L to 34.5 L against a constant pressure of 750 mmHg.

What is the work done in joules by the system?

A) 1.12 × 103 J

B) -1.12 × 103 J

C) 9.09 × 104 J

D) -9.09 × 104 J

E) 4.55 × 103 J

26) How much work, in joules, is done when the pressure is suddenly released from 4.56 atm to 1.23 atm

on 45.4 g of O2 at 44 °C?

A) 386 J

B) -477 J

C) -2.74 × 103 J

D) 2.74 × 103 J

E) 477 J

27) Which of the following are thermodynamic state functions?

I) heat

II) volume

III) temperature

IV) enthalpy

V) density

A) II, III, IV, V

B) I, II, IV, V

C) I, II, III, V

D) II, IV

E) I, III, V

28) A system absorbs 623 J of heat while doing 457 J of work. What is the value of ΔU?

A) +1080 J

B) -166 J

C) +166 J

D) -1080 J

E) +623 J

29) Enthalpy is defined as:

A) the heat of combustion

B) the energy contained within a system

C) the sum of the internal energy and the pressure-volume product of a system

D) the sum of the kinetic and potential energies

E) the work not limited to pressure volume work

30) Calculate the work needed to make room for products in the combustion of sulfur, S8(s), to SO2(g) at

STP.

A) 0 kJ

B) -2.27 kJ

C) -4.54 kJ

D) -18.2 kJ

E) +182 kJ

31) Given the following reactions:

2 NOCl(g) → 2 NO(g) + Cl2(g) ΔrH° = +75.56 kJ/mol

2 NO(g) + O2(g) → 2 NO2(g) ΔrH° = -113.05 kJ/mol

2 NO2(g) → N2O4(g) ΔrH° = -58.03 kJ/mol

Compute ΔrH° of N2O4(g) + Cl2(g) → 2 NOCl(g) + O2(g) in kJ/mol.

A) +246.65 kJ/mol

B) -95.52 kJ/mol

C) -246.65 kJ/mol

D) +95.52 kJ/mol

E) +130.58 kJ/mol

32) Calculate the standard enthalpy of formation of Cl–(aq), given the following thermochemical data at 1

atm, and knowing that the standard enthalpies of formation of H2(g) and H+(aq) are both zero.

HCl(g) → H+(aq) + Cl–(aq) ΔrH° = -75.15 kJ/mol

H2(g) + Cl2(g) → 2HCl(g) ΔrH° = -184.62 kJ/mol

A) -167.46 kJ/mol

B) +109.47 kJ/mol

C) -17.16 kJ/mol

D) +34.32 kJ/mol

E) + 167 kJ ?mol

33) From the following thermochemical equations, calculate ΔrH° for the reaction:

SO2(g) + NO2(g) → SO3(g) + NO(g)

2 SO2(g) + O2(g) → 2 SO3(g) ΔrH° = -197.8 kJ/mol

2 NO(g) + O2(g) → 2 NO2(g) ΔrH° = -114.14 kJ/mol

A) -83.66 kJ /mol

B) -311.9 kJ/mol

C) +155.9 kJ/mol

D) -155.9 kJ/mol

E) -41.83 kJ/mol

34) 2 LiOH(s) → Li2O(s) + H2O(l) ΔrH° = 379.1 kJ/mol

LiH(s) + H2O(l) → LiOH(s) + H2(g) ΔrH° = -111.0 kJ/mol

2 H2(g) + O2(g) → 2 H2O(l) ΔrH° = -285.9 kJmol

Compute ΔrH° in kJ/mol for 2 LiH(s) + O2(g) → Li2O(s) + H2O(l)

A) +125.2 kJ/mol

B) -17.7 kJ/mol

C) -128.8 kJ/mol

D) -303.6 kJ/mol

E) + 128.8 kJ/mol

35) Which of the following has a standard enthalpy of formation of zero?

A) Ar(g)

B) I2(g)

C) Br2(g)

D) O3(g)

E) P(s, red)

36) The standard enthalpy of formation of NiSO4(s) at 25 °C is –872.9 kJ/mol. The chemical equation to

which this value

A) 1/2 Ni(s) + 1/2 S(s) + 1/2 O2(g) → 1/2 NiSO4(s)

B) Ni(s) + S(s) + 4 O(g) → NiSO4(s)

C) Ni(s) + S(s) + 2 O2(g) → NiSO4(s)

D) Ni(s) + 1/8 S8(s) + 1/2 O2(g) → NiSO4(s)

E) NiSO4(s) → Ni(s) + S(s) + 4 O(g)

37) The standard enthalpy of formation for CuSO4 ∙ 5 H2O(s) is -2278.0 kJ/mol at 25 °C. The chemical

equation to which this value applies is:

A) Cu(s) + S(s) + 5 H2O(g) + 2 O2(g) → CuSO4 ∙ 5 H2O(s)

B) Cu(s) + S(s) + 9/2 O2(g) + 5 H2(g) → CuSO4 ∙ 5 H2O(s)

C) Cu(s) + SO4(g) + 5 H2O(g) → CuSO4 ∙ 5 H2O(s)

D) Cu(s) + S(s) + 5/9 O2(g) + 5 H2(g) → CuSO4 ∙ 5 H2O(s)

E) 2 Cu(s) + 2 SO2(g) + 5 H2O(g) → 2 CuSO4 ∙ 5 H2O(s)

38) The standard enthalpy of formation of NH4Cl(s) is -315.4 kJ/mol. The equation that describes this

△fH° is:

A) NH4+(aq) + Cl–(aq) → NH4Cl(s)

B) 1/2 N2(g) + 2 H2(g) + 1/2 Cl2(g) → NH4Cl(s)

C) N2(g) + H2(g) + Cl2(g) → 2 NH4Cl(s)

D) 1/2 N2(g) + 1/2 Cl2(g) + 1/2 H2(g) → NH4Cl(s)

E) N2(g) + Cl2(g) + 4 H2(g) → 2 NH4Cl(s)

39) To have a standard enthalpy of formation referenced to 0 J/mol, the substance must:

I) be a simple substance (chemical element)

II) be in its most stable form

III) be under 1 bar of pressure

IV) have a concentration of 1.0000 M

A) I, III, IV

B) I, II, III

C) II, IV

D) I, III

E) II, III, IV

40) Calculate the enthalpy change for the following reaction at 25 °C. The value of ΔfH° in kJ/mol is given

below each species:

2 Fe2O3(s) + 6 CO(g) → 4 Fe(s) + 6 CO2(g)

-824.2 -110.5 0 -393.5

A) -49.6 kJ/mol

B) 541 kJ/mol

C) -1380 kJ/mol

D) -3350 kJ/mol

E) -24.8 kJ/mol

41) Calculate the enthalpy change for the following reaction at 25 °C. The value of ΔfH° in kJ/mol is given

below each species:

Al3+ (aq) + 3 OH– (aq) → Al(OH)3(s)

–531 -230.0 -1276

A) -515 kJ/mol

B) -55 kJ/mol

C) -975 kJ/mol

D) -1120 kJ/mol

E) -2040 kJ/mol

42) Consider the reaction: 4 NH3(g) + 5 O2(g) → 4 NO2(g) + 6 H2O(l)

ΔfH° -46.19 0.00 90.37 -285.85 kJ/mol

Compute ΔrH° for this reaction.

A) -622.62 kJ/mol

B) 984.10 kJ/mol

C) -1168.9 kJ/mol

D) -241.67 kJ/mol

E) -149.29 kJ/mol

43) Calculate ΔfH° of octane, C8H18(l), given the enthalpy of combustion of octane to CO2(g) and H2O(l),

-5471 kJ/mol, and the standard enthalpies of formation of CO2(g) and H2O(l), -393.5 kJ/mol and -285.8

kJ/mol, respectively.

A) -249.2 kJ/mol

B) +4792 kJ/mol

C) +249.2 kJ/mol

D) -4792 kJ/mol

44) What is the reaction for the standard enthalpy of formation for HCl(g)?

A) H+(aq) + Cl–(aq) → HCl(g)

B) 1/2 H2(g) + 1/2 Cl2(l) → HCl(s)

C) NH3(g) + Cl2(g) → NH2Cl(g) + HCl(g)

D) 1/2 H2(g) + 1/2 Cl2(g) → HCl(g)

E) 1/2 H2(l) + 1/2 Cl2(g) → HCl(l)

45) What is the reaction for the standard enthalpy of formation for CdSO4(s)? (Cd(s) is the stable form of

cadmium.)

A) Cd(NO3)2(aq) + H2SO4(aq) → 2 HNO3(aq) + CdSO4(s)

B) Cd2+ (aq) + 2 SO42-(aq) → CdSO4(s)

C) Cd(s) + 1/8 S8 (s) + 2O2(g) → CdSO4(s)

D) CdO(s) + SO3(l) → CdSO4(s)

E) Cd(s) + 1/8 S8 (s) + 4O(g) → CdSO4(s)

46) What is the reaction for the standard enthalpy of formation for Mn2O3(s)? (Mn(s) is the stable form of

manganese.)

A) Mn(s) + 3/4 O2(g) → 1/2 Mn2O3(s)

B) MnO(s) + MnO2(s) → Mn2O3(s)

C) 2 Mn(s) + O3(g) → Mn2O3(s)

D) 2 MnO(s) + 1/2 O3(g) → Mn2O3(s)

E) 2Mn (s) + 3/2 O2 (g) → Mn2O3(s)

47) An example of a fossil fuel is:

A) the sun

B) chlorophyll

C) water

D) natural gas

E) carbon dioxide

48) Coal contains an impurity that reacts with oxygen during the combustion process, producing oxides

that are major environmental pollutants. This impurity is:

A) acid rain

B) nitrogen

C) sulfur

D) carbon dioxide

E) peat

49) The heat of combustion of several fuels are listed in the table below. On a per gram basis, which fuel

releases the most energy?

Fuel △rHcomb (kJ/mol)

C(s) -393.5

CH4(g) -890.8

CH3OH(l) 726.1

C3H8(g) 2219.2

H2(g) -285.8

A) C(s)

B) CH4(g)

C) CH3OH(l)

D) C3H8(g)

E) H2(g)

50) How much heat is needed to raise the temperature of 5.28 gal of water from 25.0 °C to 88.0 °C

(1 gal = 3.785 L)?

A) 5260 kJ

B) 997 kJ

C) 1390 kJ

D) 316 kJ

E) 133 kJ

51) The final temperature when 150 mL of water at 90.0 °C is added to 100.0 mL of water at 30.0 °C is

around ________.

A) 90 °C

B) 120 °C

C) 30 °C

D) 70 °C

E) 25 °C

52) 1674 J of heat are absorbed by 25.0 mL of NaOH (d = 1.10 g/mL, specific heat = 4.10 J/g °C). The

temperature of the NaOH goes up by how many degrees?

A) 14.8 °C

B) 18.0 °C

C) 17.2 °C

D) 14.2 °C

E) 19.1 °C

53) Calculate the quantity of heat, in kJ, required to raise the temperature of a 2.15 kg iron bar 24.0 °C

(specific heat of iron = 0.473 J/g °C).

A) 109 kJ

B) 51.6 kJ

C) 23.6 kJ

D) 24.4 kJ

E) 11.3 kJ

54) How much heat is required to raise the temperature of 175 g of aluminum from 21.0 °C to 145 °C? The

specific heat of aluminum is 0.903 J g-1 °C-1.

A) 19.6 kJ

B) 24.0 kJ

C) 1.27 J

D) 22.9 kJ

55) A 12-inch diameter ball of pure cobalt metal at 225 °C was placed in 10.0 gal. of water at 15.0 °C. What

is the final temperature of the water? Assume no heat is lost to the surroundings. (specific heat for cobalt

is 0.421 J/g °C, density of cobalt = 8.862 g/cm3, 1 gal. = 3.785 L, 1 in = 2.54 cm, V(sphere) = 4/3 πr3)

A) 169 °C

B) 120 °C

C) 69.5 °C

D) 22.5 °C

E) 45.6 °C

56) 100.0 g of nickel at 150 °C was placed in 1.00 L of water at 25.0 °C. The final temperature of the nickel-

water mixture was 26.3 °C. What is the specific heat of the nickel?

A) 0.14 J/g °C

B) 0.13 J/g °C

C) 0.55 J/g °C

D) 0.44 J/g °C

E) 0.23 J/g °C

57) 500 g of Al is heated to 100.0 °C and dropped into a l00.0 g glass beaker that contains 200.0 g of H2O.

The temperature of the glass and water is 20.0 °C. What is the final temperature? (Specific heat of Al =

0.29 J/g °C, specific heat of glass = 0.84 J/g °C)

A) 46.6 °C

B) 50.0 °C

C) 25.0 °C

D) 30.9 °C

E) 28.9 °C

58) 100.0 g of Cu (specific heat = 0.385 J/g °C) at 100.0 °C is added to 140.0 mL of H2O (specific heat =

4.184 J/g °C) at 25.0 °C. What is the final temperature of the mixture?

A) 56.3 °C

B) 29.6 °C

C) 62.5 °C

D) 91.4 °C

E) 33.7 °C

59) Calculate the amount of heat absorbed by a 40.0 g sample of water at 21 °C when the temperature is

raised to 35 °C.

A) 5.9 kJ

B) -0.56 kJ

C) 0.56 kJ

D) -2.3 kJ

E) 2.3 kJ

60) A mixture of 125 g of iron and 250 g of water is heated from 25.0 °C to 70.0 °C. How much heat is

absorbed by the mixture? (Specific heat of water = 4.18 J/g °C; iron = 0.473 J/g °C)

A) 49.7 kJ

B) 59.6 kJ

C) 47.0 kJ

D) 2.66 kJ

E) 27.6 kJ

61) 246 g of hot coffee at 86.0 °C are placed in a 137 g mug at 20.0 °C. The specific heat of coffee is 4.00 J/g

°C, while that of the mug is 0.752 J/g °C. Assuming no heat is lost to the surroundings, what is the final

temperature of the system: mug + coffee?

A) 79.7 °C

B) 93.7 °C

C) 98.4 °C

D) 76.0 °C

E) 53.0 °C

62) 250.0 g of hot coffee at 95.0 °C are placed in a 0.2000 kg mug at 20.0 °C. The specific heat of the coffee

is 4.00 J/g °C, while that of the mug is 0.80 J/g °C. Assuming no heat is lost to the surroundings, what is

the final temperature of the system: mug + coffee?

A) 61.7 °C

B) 117 °C

C) 76.0 °C

D) 57.5 °C

E) 84.7 °C

63) Many people believe that coffee may be cooled by placing a silver spoon

in the coffee. If 250 ml of coffee at 200 °F had a spoon at 70 °F

placed in it, what would be the final Celsius temperature of the spoon and coffee, assuming that no heat

is lost to the surroundings? The mass of the spoon is 35 g.

A) 92.8 °C

B) 72.2 °C

C) 57.2 °C

D) 82.0 °C

E) 199 °C

64) A sample gives off 2505 cal when burned in a bomb calorimeter. The temperature of the calorimeter

assembly increases by 2.24 °C. What is the heat capacity of the calorimeter?

A) 8.92 kcal/ °C

B) 1.12 kcal/ °C

C) 2.51 kcal/ °C

D) 5.61 kcal/ °C

E) 2.65 kcal/ °C

65) What is the heat of combustion in kJ/g of benzoic acid (C6H5COOH) if the initial temperature was

22.62 °C, the final temperature was 31.10 °C, the heat capacity of the bomb calorimeter was 4.88 kJ/ °C,

and 1.567 grams were combusted?

A) -26.4 kJ/g

B) -64.8 kJ/g

C) -9.99 kJ/g

D) -41.4 kJ/g

E) 35.5 kJ/g

66) Cyclohexanol, C6H12O, has a heat of combustion of -890.7 kcal/mol. A sample containing 0.708 g of

cyclohexanol undergoes complete combustion in a bomb calorimeter that has a heat capacity of 2.70 kcal/

°C. What is the final temperature if the initial water temperature is 27.0 °C?

A) 24.7 °C

B) 29.3 °C

C) 27.4 °C

D) 26.6 °C

E) 31.4 °C

67) 5.04 × 10-3 mole of a compound is added to 41.0 g of water in a styrofoam cup and stirred until it

dissolves. The temperature of the solution changes from 23.460 °C to 23.420 °C. What is the heat of

solution of the compound expressed in kJ/mol? Assume the specific heat of the solution is 4.18 J/g °C.

A) -0.035 kJ/mol

B) 1.4 kJ/mol

C) -1.4 kJ/mol

D) -2.8 kJ/mol

E) 2.8 kJ/mol

68) Two solutions, 250.0 mL of 1.00 M CaCl2(aq) and 250.0 mL of 1.00 M K2SO4(aq), are added to a

calorimeter with a total heat capacity, after the solutions are added, of 1.25 kJ/ °C and the temperature

decreased by 2.40 °C. Determine qrxn per mole of CaSO4(s) formed in the reaction.

A) +12.0 kJ/mol

B) -12.0 kJ/mol

C) +6.00 kJ/mol

D) -6.00 kJ/mol

69) What is the work in joules done on the system to compress He gas from 24.0 L to 12.5 L against a

pressure of 1.5 atm at a constant temperature of 37.4 °C?

A) 5.5 × 103 J

B) -17 J

C) 17 J

D) 1.7 × 103 J

E) -1.7 × 103 J

70) Calculate ΔU for a system that loses 475 kJ of heat and does 155 kJ of expansion work on the

surroundings.

A) -630 kJ

B) -320 kJ

C) +630 kJ

D) +320 kJ