Deck 7: Thermochemistry

Question 1

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

Answer 1

False

Question 2

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: q_system + q_surroundings = 0.
E)Most metals have low specific heats,as metals can be heated quickly.

Answer 2

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

Question 3

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

Answer 3

False

Question 4

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

Question 5

Enthalpy is an extensive property.

Question 6

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.

Question 7

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)

Question 8

A system that absorbs heat is an exothermic system.

Question 9

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 10

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 11

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

Question 12

Kinetic energy is the energy of motion.

Question 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.

Question 14

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

Question 15

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

Question 16

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

Question 17

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

Question 18

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 19

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

Question 20

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

Question 21

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

Question 22

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 23

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 × 10^{3 J}
D)2.74 × 10^{3 J}
E)477 ^J

Question 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 q_rxn 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 25

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 26

Calculate the enthalpy change for the following reaction at 25 °C.The value of Δ_fH° in kJ/mol is given below each species:

A)-49.6 kJ/mol
B)541 kJ/mol
C)-1380 kJ/mol
D)-3350 kJ/mol
E)-24.8 kJ/mol

Question 27

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)

Question 28

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 × 10^{3 J}
B)-8.2 × 10^{4 J}
C)8.2 × 10^{4 J}
D)1.8 × 10^{5 J}
E)-1.8 × 10^{5 J}

Question 29

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

Question 30

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)Δ_rH° = -75.15 kJ/mol
H₂(g)+ Cl₂(g)→ 2HCl(g)Δ_rH° = -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

Question 31

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 32

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)

Question 33

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 34

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 35

2 LiOH(s)→ Li₂O(s)+ H₂O(l)Δ_rH° = 379.1 kJ/mol
LiH(s)+ H₂O(l)→ LiOH(s)+ H₂(g)Δ_rH° = -111.0 kJ/mol
2 H₂(g)+ O₂(g)→ 2 H₂O(l)Δ_rH° = -285.9 kJmol
Compute Δ_rH° 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

Question 36

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

Question 37

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 × 10^{3 J}
B)-1.12 × 10^{3 J}
C)9.09 × 10^{4 J}
D)-9.09 × 10^{4 J}
E)4.55 × 10^{3 J}

Question 38

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)

Question 39

Given the following reactions:
2 NOCl(g)→ 2 NO(g)+ Cl₂(g)Δ_rH° = +75.56 kJ/mol
2 NO(g)+ O₂(g)→ 2 NO₂(g)Δ_rH° = -113.05 kJ/mol
2 NO₂(g)→ N₂O₄(g)Δ_rH° = -58.03 kJ/mol
Compute Δ_rH° 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

Question 40

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 × 10^{3 J}
B)-1.12 × 10^{3 J}
C)9.09 × 10^{4 J}
D)-9.09 × 10^{4 J}
E)4.55 × 10^{3 J}

Question 41

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 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 SO₄^2-(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)

Question 43

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

Question 44

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 45

An example of a fossil fuel is:

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

Question 46

The heat of combustion of several fuels are listed in the table below.On a per gram basis,which fuel releases the most energy?

A)C(s)
B)CH₄(g)
C)CH₃OH(l)
D)C₃H₈(g)
E)H₂(g)

Question 47

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 48

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 49

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 50

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 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

Question 52

Calculate the enthalpy change for the following reaction at 25 °C.The value of Δ_fH° in kJ/mol is given below each species:

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

Question 53

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 54

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 55

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 56

Calculate Δ_fH° 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 57

Consider the reaction:

Compute Δ_rH° 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

Question 58

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)

Question 59

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

Question 60

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 61

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 62

The complete combustion of propane,C₃H₈(g),is represented by the equation:
C₃H₈(g)+ 5 O₂(g)→ 3 CO₂(g)+ 4 H₂O(l)Δ_rH° = -2220 kJ /mol
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 63

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 64

Complete combustion of 75.0 g acetylene,C₂H₂,liberated 3750 kJ of heat.What is the heat of combustion,Δ_rH_comb,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 65

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 × 10^{3 J}
B)-17 ^J
C)17 ^J
D)1.7 × 10^{3 J}
E)-1.7 × 10^{3 J}

Question 66

For the reaction H₂(g)+ 1/2 O₂(g)→ H₂O(g)Δ_rH° = -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 67

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

Question 68

For the reaction H₂(g)+ 1/2 O₂(g)→ H₂O(g)Δ_rH° = -241.8 kJ/mol,
What quantity of heat,in kJ,evolved when a 72.0 g mixture containing equal parts of H₂ and O₂,by mass,is burned?

A)8630 kJ
B)4860 kJ
C)1088 kJ
D)272 kJ
E)544 kJ

Question 69

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 q_rxn 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 70

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 71

The complete combustion of propane,C₃H₈(g),is represented by the equation:
C₃H₈(g)+ 5 O₂(g)→ 3 CO₂(g)+ 4 H₂O(l)Δ_rH° = -2220 kJ /mol
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)1957 kJ
E)495 kJ

Question 72

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

Question 73

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

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

Question 74

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 75

The complete combustion of propane,C₃H₈(g),is represented by the equation:
C₃H₈(g)+ 5 O₂(g)→ 3 CO₂(g)+ 4 H₂O(l)Δ_rH° = -2220 kJ/mol
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 76

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

Question 77

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

Question 78

For the reaction H₂(g)+ 1/2 O₂(g)→ H₂O(g)Δ_rH° = -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 79

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

Question 80

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