Deck 7: Thermochemistry

Question 1

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.

Answer 1

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

Question 2

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

Answer 2

False

Question 3

1219 joules of heat raise the temperature of 250 g of metal by 64°C. What is the specific heat 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 x 64) J/(g°C)

Answer 3

(1219)/(250 x 64) J/(g°C)

Question 4

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

Question 5

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

Question 6

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

Question 7

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

Question 8

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

Question 9

A system that absorbs heat is an exothermic system.

Question 10

Enthalpy is an extensive property.

Question 11

The enthalpy of a system is the internal energy minus work

Question 12

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.

Question 13

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) [(914.0)(0.105)/250] + 24.0 °C
D) (14.0)(0.105)/250 °C
E) (14.0)(0.105)(250) °C

Question 14

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

Question 15

The maximum amount of work is provided by a reversible process because equilibrium between the system and the surroundings is always maintained.

Question 16

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

Question 17

Kinetic energy is the energy of motion.

Question 18

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

Question 19

What is the final temperature in the bomb calorimeter if 1.785 grams of benzoic acid (HC7H5O2) 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) 33.7°C

Question 20

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 = P ∙ V.
E) Heat moves from a warmer body to a colder one.

Question 21

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

Question 22

2 NOCl(g) → 2 NO(g) + Cl2(g) ΔH° = +75.56 kJ 2 NO(g) + O2(g) → 2 NO2(g) ΔH° = -113.05 kJ
2 NO2(g) → N2O4(g) ΔH° = -58.03 kJ
Compute ΔH° of N2O4(g) + Cl2(g) → 2 NOCl(g) + O2(g) in kJ.

A) +246.65
B) -95.52
C) -246.65
D) +95.52
E) none of these

Question 23

From the following thermochemical equations, calculate ΔH°rxn for the reaction: SO2(g) + NO2(g) → SO3(g) + NO(g)
2 SO2(g) + O2(g) → 2 SO3(g) ΔH°rxn = -197.8 kJ
2 NO(g) + O2(g) → 2 NO2(g) ΔH°rxn = -114.14 kJ

A) -83.66 kJ
B) -311.9 kJ
C) +155.9 kJ
D) -155.9 kJ
E) -41.83 kJ

Question 24

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 atm 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

Question 25

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

Question 26

2 LiOH(s) → Li2O(s) + H2O(l) ΔH° = 379.1 kJ LiH(s) + H2O(l) → LiOH(s) + H2(g) ΔH° = -111.0 kJ
2 H2(g) + O2(g) → 2 H2O(l) ΔH° = -285.9 kJ
Compute ΔH° in kJ for 2 LiH(s) + O2(g) → Li2O(s) + H2O(l)

A) +125.2 kJ
B) -17.7 kJ
C) -128.8 kJ
D) -303.6 kJ
E) + 128.8 kJ

Question 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

Question 28

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) -75.15 kJ
H2(g) + Cl2(g) → 2HCl(g) -184.62 kJ

A) -167.46 kJ/mol
B) +109.47 kJ/mol
C) -17.16 kJ/mol
D) +34.32 kJ/mol

Question 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

Question 30

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

Question 31

The standard enthalpy of formation for CuSO4 ∙ 5H2O(s) is -2278.0 kJ/mole at 25°C. The chemical equation to which this value applies is:

A) Cu(s) + S(s) + 5 H2O(g) + 2 O2(g) → CuSO4 ∙ 5H2O(s)
B) Cu(s) + S(s) + 9/2 O2(g) + 5 H2(g) → CuSO4 ∙ 5H2O(s)
C) Cu(s) + SO4(g) + 5 H2O(g) → CuSO4 ∙ 5H2O(s)
D) Cu(s) + S(s) + 5/9 O2(g) + 5 H2(g) → CuSO4 ∙ 5H2O(s)
E) 2Cu(s) + 2 SO2(g) + 5 H2O(g) → 2CuSO4 ∙ 5H2O(s)

Question 32

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

Question 33

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

Question 34

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)

Question 35

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

Question 36

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

Question 37

How much work, in joules, is done when the pressure is suddenly released from 2.05 atm to 1.87 atm on 27.5 g of He at 27°C?

A) 5.2 × 103 J
B) -8.0 × 103 J
C) 8.0 × 103 J
D) -1.5 × 103 J
E) 1.5 × 103 J

Question 38

The standard enthalpy of formation of NiSO4(s) at 25 °C is -872.9 kJ/mole. The chemical equation to which this value applies is:

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)

Question 39

The standard enthalpy of formation of NH4Cl(s) is -315.4 kJ/mol. The equation that describes this △H°f is:

A) NH4+(aq) + Cl-(aq) → NH4Cl(s)
B) 1/2 N2(g) + 2H2(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)

Question 40

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

Question 41

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. (sp ht 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) 69.3°C
D) 22.5°C
E) 45.6°C

Question 42

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- → 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)

Question 43

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) + 1/2Cl2(l) → HCl(s)
C) NH3(g) + Cl2(g) → NH2Cl(g) + HCl(g)
D) 1/2 H2(g) + 1/2Cl2(g) → HCl(g)
E) 1/2 H2(l) + 1/2Cl2(g) → HCl(l)

Question 44

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

Question 45

Calculate the enthalpy change for the following reaction at 25°C. The value of ΔH°f in kJ/mol is given below each species: Al3+ (aq) + 3 OH- (aq) → Al(OH)3(s)
-531 -230.0 -1276

A) -515 kJ
B) -55 kJ
C) -975 kJ
D) -1120 kJ
E) -2040 kJ

Question 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)

Question 47

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 how many degrees?

A) 14.8 °C
B) 18.0 °C
C) 17.2 °C
D) 14.2 °C
E) 19.1 °C

Question 48

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

Question 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 △Hcomb (kJ/mole)
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)

Question 50

An example of a fossil fuel is:

A) the sun
B) chlorophyll
C) water
D) natural gas
E) carbon dioxide

Question 51

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

Question 52

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

Question 53

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

Question 54

Calculate the enthalpy change for the following reaction at 25°C. The value of ΔH°f 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
B) 541 kJ
C) -1380 kJ
D) -3350 kJ
E) -24.8 kJ

Question 55

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

Question 56

Consider the reaction: 4 NH3(g) + 5 O2(g) → 4 NO2(g) + 6 H2O(l) ΔH°f -46.19 0.00 90.37 -285.85 kJ/mol
Compute ΔH° for this reaction.

A) -622.62 kJ
B) 984.10 kJ
C) -1168.9 kJ
D) -241.67 kJ
E) -149.29 kJ

Question 57

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

Question 58

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

Question 59

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) 60 °C
E) 25 °C

Question 60

Calculate ΔH°f 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

Question 61

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

Question 62

What is the heat of combustion in kJ/g of benzoic acid (HC7H5O2) 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
B) -64.8
C) -9.99
D) -41.4
E) 35.5

Question 63

Cyclohexanol, C6H12O, has a heat of combustion of -890.7 kcal/mol. A sample containing only 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

Question 64

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

Question 65

A certain reaction releases 10.1 kJ at constant volume and at constant pressure releases 8.4 kJ. What is △U for the reaction?

A) -10.1 kJ
B) -8.4 kJ
C) +8.4 kJ
D) -1.7 kJ

Question 66

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

Question 67

The complete combustion of propane, C3H8(g), is represented by the equation: C3H8(g) + 5 O2(g) → 3 CO2(g) + 4 H2O(l) ΔH° = -2220 kJ
How much heat is evolved in the complete combustion of 2.50 g C3H8(g)?

A) 245 kJ
B) 50.4 kJ
C) 126 kJ
D) 5.56 kJ
E) 2.22 kJ

Question 68

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

Question 69

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

Question 70

For the reaction H2(g) + 1/2 O2(g) → H2O(g) ΔH° = -241.8 kJ/mol, what mass of H2(g) is required to liberate 1.00 × 103 kJ of heat?

A) 66.2 g
B) 4.17 g
C) 8.34 g
D) 2.05 g
E) 16.7 g

Question 71

Complete combustion of 75.0 g acetylene, C2H2, liberated 3750 kJ of heat. What is the heat of combustion, ΔHcomb, of acetylene?

A) -50.0 kJ/mol
B) +50.0 kJ/mol
C) +1302 kJ/mol
D) -1302 kJ/mol
E) -0.521 kJ/mol

Question 72

The heat of combustion of methane is -50.38 kJ/mol. How many moles of methane must be burned to produce 137 kJ of heat?

A) 6.90 mol
B) 0.367 mol
C) 2.72 mol
D) 1.37 mol
E) 0.272 mol

Question 73

Many people believe that coffee (sp ht = 4.18 J/g °C) may be cooled by placing a silver spoon (sp ht = 0.237 J/g °C) in the coffee. If 250 ml (d = 1.00 g/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) 92.2°C
B) 72.2°C
C) 57.2°C
D) 82.0°C
E) 199°C

Question 74

A sample gives off 2505 cal when burned in a bomb calorimeter. 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

Question 75

The complete combustion of propane, C3H8(g), is represented by the equation: C3H8(g) + 5 O2(g) → 3 CO2(g) + 4 H2O(l) ΔH° = -2220 kJ
How much heat is evolved in the complete combustion of 20.0 L C3H8(g) at STP?

A) 2486 kJ
B) 1007 kJ
C) 994 kJ
D) 1982 kJ
E) 495 kJ

Question 76

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 J/mol
B) 1.4 kJ/mol
C) -1.4 kJ/mol
D) -2.8 kJ/mol
E) 2.8 kJ/mol

Question 77

If 356 J of work is done by a system while it loses 289 J of heat, what is the value of ΔU ?

A) +645 J
B) -645 J
C) +67 J
D) -67 J
E) +134 J

Question 78

The complete combustion of propane, C3H8(g), is represented by the equation: C3H8(g) + 5 O2(g) → 3 CO2(g) + 4 H2O(l) ΔH° = -2220 kJ
How much heat is evolved in the complete combustion of 12.5 L C3H8(g) at 25°C and 790 mmHg?

A) 8.27 × 104 kJ
B) 1.41 × 104 kJ
C) 653 kJ
D) 168 kJ
E) 1180 kJ

Question 79

For the reaction H2(g) + 1/2 O2(g) → H2O(g) ΔH° = -241.8 kJ/mol, what quantity of heat is liberated by the reaction of 10.0 L of O2 measured at 22.0°C and 742 mmHg?

A) 120 kJ
B) 2610 kJ
C) 1310 kJ
D) 195 kJ
E) 97.5 kJ

Question 80

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