Deck 6: Thermochemistry

Question 1

What is the change in internal energy of the system (ΔU)if 71 kJ of heat energy is absorbed by the system and 12 kJ of work is done on the system for a certain process?

A)83 kJ
B)59 kJ
C)71 kJ
D)-83 kJ
E)-59 kJ

Answer 1

83 kJ

Question 2

Which of the following statements about enthalpy is false?

A)Enthalpy is a state function.
B)At constant pressure,the enthalpy change is equal to the heat absorbed or released.
C)Enthalpy is an extensive property.
D)The change in enthalpy of a process cannot be negative.
E)The SI unit of enthalpy is J.

Answer 2

The change in enthalpy of a process cannot be negative.

Question 3

If q = -96 kJ for a certain process,that process

A)requires a catalyst.
B)is exothermic.
C)occurs rapidly.
D)is endothermic.
E)cannot occur.

Answer 3

is exothermic.

Question 4

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

Question 5

H₂ and F₂ react according to the following equation,forming HF.
H₂(g)+ F₂(g)→ 2HF(g); ΔH° = -271 kJ
If H₂(g)and F₂(g)were mixed in a thermally insulated vessel,the reaction that occurred would be

A)endothermic,and the temperature of the reaction system would fall.
B)We could not tell unless the original and final temperatures were given.
C)exothermic,and the temperature of the reaction system would fall.
D)exothermic,and the temperature of the reaction system would rise.
E)endothermic,and the temperature of the reaction system would rise.

Question 6

Which of the following statements about heat is false?

A)If heat flows into a system,the extra energy of the system appears in the form of internal energy.
B)A hot object possesses more heat than a cold object.
C)If the system and surroundings are in thermal equilibrium,there is no heat flow between them.
D)A process in which heat flows out of a system is said to be exothermic.
E)Heat is a form of energy flow.

Question 7

Which of the following statements is incorrect?

A)Internal energy is a state function.
B)The value of q is positive when heat flows into a system from the surroundings.
C)The value of q is positive in an endothermic process.
D)Heat flows from a system into the surroundings in an endothermic process.
E)Enthalpy is a state function.

Question 8

Which of the following statements is true concerning the decomposition of liquid water to form hydrogen gas and oxygen gas?
2H₂O(l)→ 2H₂(g)+ O₂(g)

A)ΔH is greater than ΔU because the pressure is constant.
B)ΔH is less than ΔU because of the pressure-volume work done by the gaseous products.
C)ΔH is less than ΔU because the atmosphere does pressure-volume work on the gaseous products.
D)ΔH equals ΔU because both are state functions.
E)ΔH is greater than ΔU because of the pressure-volume work done by the gaseous products.

Question 9

At constant pressure,the sign of q for the process CO₂(s)→ CO₂(g)is expected to be

A)positive,and the process is exothermic.
B)negative,and the process is exothermic.
C)impossible to predict.
D)positive,and the process is endothermic.
E)negative,and the process is endothermic.

Question 10

What is the kinetic energy of a 2000-lb car traveling at 59 miles per hour? (1 lb = 0.4536 kg,1 mi = 1.609 km)

A)3.2 × 10^-7 J
B)1.5 × 10⁶ J
C)5.3 × 10¹⁹ J
D)3.2 × 10⁵ J
E)4.7 × 10^-8 J

Question 11

The skydiver plunging to earth possesses what type(s)of energy?

A)potential energy only
B)internal energy only
C)kinetic energy only
D)kinetic energy,potential energy,and internal energy
E)kinetic energy and potential energy only

Question 12

The internal energy of a substance is defined as

A)the potential energy of all particles which make up the substance.
B)the kinetic energy of all particles which make up the substance.
C)the sum of the potential and kinetic energy of all particles which make up the substance.
D)the thermal energy of all particles which make up the substance.
E)the chemical energy of all particles which make up the substance.

Question 13

The energy associated with an object held above the surface of the earth is called _____.

A)heat
B)internal energy
C)temperature
D)kinetic energy
E)potential energy

Question 14

The phrase "the heat absorbed or released by a system undergoing a physical or chemical change at constant pressure" is

A)the change in enthalpy of the system.
B)the change in internal energy of the system.
C)the definition of a state function.
D)the temperature change of the system.
E)a statement of Hess's law.

Question 15

Which of the following does not result in a change in the internal energy of the system?

A)work is done on the system
B)work is done on the surroundings
C)heat flows into the system
D)heat flows to the surroundings
E)none of the above

Question 16

Calculate ΔU of a gas for a process in which the gas absorbs 29 J of heat and does 31 J of work by expanding.

A)2 J
B)60 J
C)-60 J
D)0,because ΔU is a state function
E)-2 J

Question 17

At constant pressure,the sign of q for the process H₂O(l)→ H₂O(s)is expected to be

A)positive,and the process is exothermic.
B)negative,and the process is endothermic.
C)impossible to predict.
D)negative,and the process is exothermic.
E)positive,and the process is endothermic.

Question 18

The energy associated with the motion of molecules in a gas is called _____.

A)heat
B)internal energy
C)temperature
D)kinetic energy
E)potential energy

Question 19

Which of the following statements is not true for an exothermic reaction?

A)The products have a higher heat content than the reactants.
B)The temperature of the reaction system increases.
C)The temperature of the surroundings increases.
D)Heat passes from the reaction system to the surroundings.
E)The enthalpy change for the reaction is negative.

Question 20

If q = 60 kJ and w = 96 kJ for a certain process,that process

A)requires a catalyst.
B)is endothermic.
C)occurs slowly.
D)is exothermic.
E)cannot occur.

Question 21

What is the quantity of heat evolved at constant pressure when 30.5 g H₂O(l)is formed from the combustion of H₂(g)and O₂(g)?
H₂(g)+
O₂(g)→ H₂O(l); ΔH° = -285.8 kJ

A)5.92 × 10^-3 kJ
B)285.8 kJ
C)8.72 × 10³ kJ
D)168 kJ
E)4.84 × 10² kJ

Question 22

What is the change in enthalpy when 9.00 mol of sulfur trioxide decomposes to sulfur dioxide and oxygen gas?
2SO₂(g)+ O₂(g)→ 2SO₃(g); ΔH° = 198 kJ

A)891 kJ
B)-198 kJ
C)-891 kJ
D)198 kJ
E)1782 kJ

Question 23

When 56.8 g of lead reacts with 3.50 L of oxygen gas,measured at 1.00 atm and 25.0°C,60.1 kJ of heat is released at constant pressure.What is ΔH° for this reaction? (R = 0.0821 L • atm/(K • mol))
2Pb(s)+ O₂(g)→ 2PbO(s)

A)-4.39 × 10² kJ
B)-8.7 × 10¹ kJ
C)-6.01 × 10¹ kJ
D)-2.19 × 10² kJ
E)-4.2 × 10² kJ

Question 24

Under conditions of constant pressure,for which of the following reactions is the magnitude of pressure-volume work going to be smallest?

A)BaO(s)+ SO₃(g)→ BaSO₄(s)
B)2NO(g)+ O₂(g)→ 2NO₂(g)
C)2H₂O₂(l)→ 2H₂O(l)+ O₂(g)
D)2KClO₃(s)→ 2KCl(s)+ 3O₂(g)
E)H₂(g)+ Cl₂(g)→ 2HCl(g)

Question 25

Under conditions of constant pressure,for which of the following reactions is the magnitude of pressure-volume work going to be greatest?

A)BaO(s)+ SO₃(g)→ BaSO₄(s)
B)2NO(g)+ O₂(g)→ 2NO₂(g)
C)2H₂O₂(l)→ 2H₂O(l)+ O₂(g)
D)2KClO₃(s)→ 2KCl(s)+ 3O₂(g)
E)H₂(g)+ Cl₂(g)→ 2HCl(g)

Question 26

How much heat is evolved upon the complete oxidation of 6 g of aluminum at 25°C and 1 atm pressure? ( for Al₂O₃ is -1676 kJ/mol.)
4Al(s)+ 3O₂(g)→ 2Al₂O₃(s)

A)9.238 × 10³ kJ
B)342.3 kJ
C)684.7 kJ
D)171.1 kJ
E)85.59 kJ

Question 27

Which of the following statements is incorrect concerning the thermochemical equation below?
2SO₃(g)→ 2SO₂(g)+ O₂(g); ΔH° = 198 kJ

A)The enthalpy of the reactants exceeds that of the products.
B)The reaction is endothermic.
C)For the reaction 2SO₂(g)+ O₂(g)→ 2SO₃(g),ΔH° = -198 kJ.
D)The external pressure is 1 atm.
E)For every mole of SO₃(g)consumed,99 kJ of heat at constant pressure is consumed as well.

Question 28

How much heat is liberated at constant pressure if 0.833 g of calcium carbonate reacts with 59.7 mL of 0.251 M hydrochloric acid?
CaCO₃(s)+ 2HCl(aq)→ CaCl₂(aq)+ H₂O(l)+ CO₂(g); ΔH° = -15.2 kJ

A)0.113 kJ
B)0.24 kJ
C)12.6 kJ
D)0.126 kJ
E)3.81 kJ

Question 29

According to the following thermochemical equation,if 403.3 g of NO₂ is produced,how much heat is released at constant pressure?
2NO(g)+ O₂(g)→ 2NO₂(g); ΔH° = -114.4 kJ

A)114.4 kJ
B)5.014 × 10² kJ
C)1.003 × 10³ kJ
D)13.04 kJ
E)4.614 × 10⁴ kJ

Question 30

What quantity,in moles,of oxygen is consumed when 717.4 kJ of energy is evolved from the combustion of a mixture of H₂(g)and O₂(g)?
H₂(g)+
O₂(g)→ H₂O(l); ΔH° = -285.8 kJ

A)1.255 mol
B)2.519482 mol
C)0.1991 mol
D)1.755 mol
E)0.7559321 mol

Question 31

Consider the following thermochemical equation:
N₂(g)+ 2O₂(g)→ 2NO₂(g); ΔH° = 66.2 kJ
From this equation,we may conclude that 66.2 kJ is the quantity of heat that is

A)gained from the surroundings when 1 mol of NO₂ is formed at constant pressure.
B)lost to the surroundings when 1 mol of NO₂ is formed at constant pressure.
C)gained from the surroundings when 2 mol of NO₂ is formed at constant pressure.
D)lost to the surroundings when 2 mol of NO₂ is formed at constant pressure.
E)lost to the surroundings when 1 mol of O₂ is consumed at constant pressure.

Question 32

Given:
4AlCl₃(s)+ 3O₂(g)→ 2Al₂O₃(s)+ 6Cl₂(g); ΔH = -529.0 kJ
Determine ΔH for the following thermochemical equation.
Cl₂(g)+ Al₂O₃(s)→ AlCl₃(s)+O₂(g)

A)+264.5 kJ
B)+529.0 kJ
C)+88.2 kJ
D)+176.3 kJ
E)-176.3 kJ

Question 33

What is the change in enthalpy at 25°C and 1 atm for the production of 3.00 mol SnO(s)?
Sn(s)+ SnO₂(s)→ 2SnO(s); ΔH° = 16.2 kJ

A)24.2 kJ
B)-16.2 kJ
C)16.2 kJ
D)5.4 kJ
E)24.3 kJ

Question 34

In a certain experiment,0.7000 mol of hydrogen gas reacted with 0.7000 mol of solid iodine at a constant 1 atm pressure,producing 1.4000 mol of solid hydrogen iodide and absorbing 36.9 kJ of heat in the process.Which of the following thermochemical equations correctly describes this experiment?

A)H2(g)+ I2(s)→ 2HI(s); ΔH° = -52.72 kJ
B)H₂(g)+ I₂(s)→ 2HI(s); ΔH° = 36.9 kJ
C)H₂(g)+ I₂(s)→ 2HI(s); ΔH° = -36.9 kJ
D)H₂(g)+ I₂(s)→ 2HI(s); ΔH° = 73.8 kJ
E)H₂(g)+ I₂(s)→ 2HI(s); ΔH° = 52.72 kJ

Question 35

Which of the following statements is false concerning the reaction of hydrogen gas and oxygen gas given below?
H₂(g)+
O₂(g)→ H₂O(l); ΔH = -285.8 kJ

A)Per mole of O₂,the change in enthalpy is -571.6 kJ.
B)The value -571.6 kJ pertains to 1 mol of liquid water.
C)If the equation is reversed,ΔH becomes +285.8 kJ.
D)If the equation is multiplied by 2,ΔH becomes -571.6 kJ.
E)For the reaction H₂(g)+ O₂(g)→ H₂O(g),ΔH is not equal to -285.8 kJ.

Question 36

Given: what is ΔH for the following thermochemical equation?

A)986.9 kJ
B)-986.9 kJ
C)-139 MJ
D)-2320 kJ
E)-38.7 kJ

Question 37

Which of the following sentences accurately describes the thermochemical equation given below?
2Ag(s)+ F₂(g)→ 2AgF(s); ΔH = -409.2 kJ

A)If 2 mol of silver metal react with 1 mol of fluorine gas at constant volume,2 mol of solid sodium fluoride is produced and 409.2 kJ of heat is consumed.
B)If 2 atoms of silver metal react with 1 molecule of fluorine gas at constant pressure,2 formula units of solid sodium fluoride are produced and 409.2 kJ of heat is released.
C)If 2 atoms of silver metal react with 1 molecule of fluorine gas at constant pressure,2 formula units of solid sodium fluoride are produced and 409.2 kJ of heat is consumed.
D)If 2 mol of silver metal react with 1 mol of fluorine gas at constant pressure,2 mol of solid sodium fluoride is produced and 409.2 kJ of heat is consumed.
E)If 2 mol of silver metal react with 1 mol of fluorine gas at constant pressure,2 mol of solid sodium fluoride is produced and 409.2 kJ of heat is released.

Question 38

What is the change in enthalpy at 25°C and 1 atm for the reaction of 5.00 mol of elemental iron with excess oxygen gas?
4Fe(s)+ 3O₂(g)→ 2Fe₂O₃(s); ΔH° = -1651 kJ

A)−1651 kJ
B)2751 kJ
C)206 kJ
D)2063 kJ
E)−412.8 kJ

Question 39

Given the thermochemical equation
2Al(s)+
O₂(g)→ Al₂O₃(s); ΔH = -1676 kJ
Find ΔH for the following reaction.
2Al₂O₃(s)→ 4Al(s)+ 3O₂(g)

A)838 kJ
B)1676 kJ
C)-1676 kJ
D)3352 kJ
E)-838 kJ

Question 40

What mass of oxygen is consumed when 285.5 kJ of energy is evolved from the combustion of a mixture of H₂(g)and O₂(g)?
H₂(g)+
O₂(g)→ H₂O(l); ΔH° = -285.8 kJ

A)15.98 g
B)31.96 g
C)0.01564 g
D)31.98 g
E)0.01679 g

Question 41

A 3.540-g sample of an unknown metal M is burned in the presence of excess oxygen,producing the oxide M₂O₃(s)and liberating 18.56 kJ of heat at constant pressure.What is the identity of the metal?
4M(s)+ 3O₂(g)→ 2M₂O₃(s)
Substance
ΔH°_f (kJ/mol)
Yb₂O₃(s)
-1814.6
Tb₂O₃(s)
-1865.2
Sm₂O₃(s)
-1823.0
Sc₂O₃(s)
-1908.8
Y₂O₃(s)
-1905.3

A)Sm
B)Yb
C)Y
D)Sc
E)Tb

Question 42

A 1.67-g sample of solid silver reacted in excess chlorine gas to give a 2.21-g sample of pure solid AgCl.The heat given off in this reaction was 1.96 kJ at constant pressure.Given this information,what is the enthalpy of formation of AgCl(s)?

A)127 kJ/mol
B)-63.5 kJ/mol
C)12.7 kJ/mol
D)1.96 kJ/mol
E)196 kJ/mol

Question 43

At constant pressure and 25°C,what is ΔH° for the following reaction
2C₂H₆(g)+ 7O₂(g)→ 4CO₂(g)+ H₂O(l)
If the complete consumption of 38.2 g of C₂H₆ liberates 1981 kJ of heat energy?

A)3120 kJ
B)1560 kJ
C)5030 kJ
D)2510 kJ
E)784.05 kJ

Question 44

The reaction of iron with hydrochloric acid is represented by the following thermochemical equation.
Fe(s)+ 2HCl(aq)→ FeCl₂(aq)+ H₂(g); ΔH° = -87.9 kJ
How much heat is liberated at constant pressure if 0.154 g of iron reacts with 25.7 mL of 0.358 M HCl?

A)1.85 kJ
B)13.5 kJ
C)0.242 kJ
D)0.404 kJ
E)87.9 kJ

Question 45

A 8.22-g sample of solid calcium reacted in excess fluorine gas to give a 16-g sample of pure solid CaF₂.The heat given off in this reaction was 251 kJ at constant pressure.Given this information,what is the enthalpy of formation of CaF₂(s)?

A)251 kJ/mol
B)250 kJ/mol
C)-1.23 × 10³ kJ/mol
D)-613 kJ/mol
E)1.23 × 10³ kJ/mol

Question 46

How much heat is released at constant pressure if 12.3 mL of 0.161 M silver nitrate is mixed with 41.7 mL of 0.493 M potassium chloride?
AgNO₃(aq)+ KCl(aq)→ AgCl(s)+ KNO₃(aq); ΔH° = -65.5 kJ

A)0.129 kJ
B)32.2 kJ
C)1.34 kJ
D)10.5 kJ
E)1.47 kJ

Question 47

When 22.0 mL of liquid benzene (C₆H₆,d = 0.879 g/mL)reacts with 34.2 L of oxygen gas,measured at 1.00 atm pressure and 25°C,6.09 × 10² kJ of heat is released at constant pressure.What is ΔH° for the following reaction? (R = 0.0821 L • atm/(K • mol))
2C₆H₆(l)+ 15O₂(g)→ 12CO₂(g)+ 6H₂O(l)

A)-2.84 × 10¹ kJ
B)-3.7 × 10² kJ
C)-4.92 × 10³ kJ
D)-4.36 × 10² kJ
E)-6.53 × 10³ kJ

Question 48

The specific heat capacity of water(liquid)is 4.18 J/g⋅°C.What is the molar specific heat capacity of this substance? The molar mass of water is 18.01 g/mol.

A)75.2 J/mol⋅°C
B)0.232 J/mol⋅°C
C)4.303 J/mol⋅°C
D)4.18 J/mol⋅°C
E)0.239 J/mol⋅°C

Question 49

The quantity of heat required to raise the temperature of a sample of a substance by 1°C is the sample's

A)work.
B)calorimetry.
C)heat capacity.
D)specific heat.
E)enthalpy.

Question 50

How much heat is liberated at constant pressure when 97.7 g of calcium oxide reacts with 29.0 L of carbon dioxide gas,measured at 1.00 atm pressure and 25.0°C? (R = 0.0821 L • atm/(K • mol))
CaO(s)+ CO₂(g)→ CaCO₃(s); ΔH° = -178.3 kJ

A)-3.11 × 10² kJ
B)-1.74 × 10⁴ kJ
C)-5.22 × 10² kJ
D)-2.11 × 10² kJ
E)-5.17 × 10³ kJ

Question 51

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.

Question 52

The reaction of iron with hydrochloric acid is represented by the following thermochemical equation.
Fe(s)+ 2HCl(aq)→ FeCl₂(aq)+ H₂(g); ΔH° = -87.9 kJ
In which of the following experiments would the temperature rise the most?

A)2.2 g of Fe added to 1.0 L of 0.03 M HCl
B)1.1 g of Fe added to 1.0 L of 0.02 M HCl
C)4.5 g of Fe added to 1.0 L of 0.03 M HCl
D)1.1 g of Fe added to 1.0 L of 0.04 M HCl
E)0.56 g of Fe added to 1.0 L of 0.02 M HCl

Question 53

The reaction of iron with hydrochloric acid is represented by the following thermochemical equation.
Fe(s)+ 2HCl(aq)→ FeCl₂(aq)+ H₂(g); ΔH° = -87.9 kJ
If,in a particular experiment,1.56 kJ of heat was released at constant pressure,what volume of H₂(g),measured at STP,was produced? (R = 0.0821 L • atm/(K • mol))

A)1.38 × 10³ L
B)0.434 L
C)22.4 L
D)1.26 × 10³ L
E)0.397 L

Question 54

The heat required to raise the temperature of 54.94 g of manganese by 1°C is called its

A)heat of vaporization.
B)specific heat.
C)heat of fusion.
D)entropy.
E)molar heat capacity.

Question 55

The units for specific heat are

A)J/(g ∙ °C).
B)(J ∙ °C).
C)J/g.
D)J/°C.
E)(J ∙ g).

Question 56

The units for heat capacity are

A)J/g.
B)(J ∙ g).
C)J/°C.
D)(J ∙ °C).
E)J/(g ∙ °C).

Question 57

When 13.8 mL of 0.870 M lead(II)nitrate reacts with 90.0 mL of 0.777 M sodium chloride,0.279 kJ of heat is released at constant pressure.What is ΔH° for this reaction?
Pb(NO₃)₂(aq)+ 2NaCl(aq)→ PbCl₂(s)+ 2NaNO₃(aq)

A)23.3 kJ
B)4 kJ
C)1.84 kJ
D)3.41 kJ
E)8 kJ

Question 58

A 100 g sample of each of the following metals is heated from 35°C to 45°C.Which metal absorbs the lowest amount of heat energy?
Metal
Specific Heat
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)lead
B)magnesium
C)silver
D)mercury
E)copper

Question 59

Two metals of equal mass with different heat capacities are subjected to the same amount of heat.Which undergoes the smaller change in temperature?

A)The metal with the higher heat capacity undergoes the smaller change in temperature.
B)Both undergo the same change in temperature.
C)You need to know the initial temperatures of the metals.
D)You need to know which metals you have.
E)The metal with the lower heat capacity undergoes the smaller change in temperature.

Question 60

The molar heat capacity of gaseous heptane at 25.0°C is 165.2 J/(mol ∙ °C).What is its specific heat?

A)0.6065 J/(g ∙ °C)
B)1.648 J/(g ∙ °C)
C)6.041 × 10^-5 J/(g ∙ °C)
D)165.2 J/(g ∙ °C)
E)1.655 × 10⁴ J/(g ∙ °C)

Question 61

Which of the following processes will result in the lowest final temperature of the metal-water mixture at equilibrium? The specific heat of cobalt is 0.421 J/(g ∙ °C).

A)the addition of 100 g of cobalt at 95°C to 80 mL of water at 25°C in an insulated container
B)the addition of 100 g of cobalt at 95°C to 100 mL of water at 25°C in an insulated container
C)the addition of 100 g of cobalt at 95°C to 40 mL of water at 25°C in an insulated container
D)the addition of 100 g of cobalt at 95°C to 20 mL of water at 25°C in an insulated container
E)the addition of 100 g of cobalt at 95°C to 60 mL of water at 25°C in an insulated container

Question 62

Exactly 209.2 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)0.598 J/(g ∙ °C)
B)1.67 J/(g ∙ °C)
C)14.7 J/(g ∙ °C)
D)50.0 J/(g ∙ °C)
E)none of these

Question 63

A 110.0-g sample of metal at 82.00°C is added to 110.0 g of H₂O(l)at 27.00°C in an insulated container.The temperature rises to 30.56°C.Neglecting the heat capacity of the container,what is the specific heat of the metal? The specific heat of H₂O(l)is 4.18 J/(g ∙ °C).

A)4.18 J/(g ∙ °C)
B)60.4 J/(g ∙ °C)
C)0.289 J/(g ∙ °C)
D)0.28 J/(g ∙ °C)
E)14.4 J/(g ∙ °C)

Question 64

A 58.7-g sample of nickel (s = 0.443 J/(g ∙ °C)),initially at 147.4°C,is placed in an insulated vessel containing 184.0 g of water (s = 4.18 J/(g ∙ °C)),initially at 29.9°C.Once equilibrium is reached,what is the final temperature of the metal-water mixture? Neglect the heat capacity of the vessel.

A)33.7°C
B)58.3°C
C)25.8°C
D)88.7°C
E)41.2°C

Question 65

Given:
Fe₂O₃(s)+ 3CO(g)→ 2Fe(s)+ 3CO₂(g); ΔH° = -26.8 kJ
FeO(s)+ CO(g)→ Fe(s)+ CO₂(g); ΔH° = -16.5 kJ
Determine ΔH° for the following thermochemical equation.
Fe₂O₃(s)+ CO(g)→ 2FeO(s)+ CO₂(g)

A)6.2 kJ
B)10.3 kJ
C)22.7 kJ
D)-10.3 kJ
E)-43.3 kJ

Question 66

When 0.0500 mol of HCl(aq)is reacted with 0.0500 mol of NaOH(aq)in 50.0 mL of water,the temperature of the solution increases by 5.99°C.What is the enthalpy of reaction for the following thermochemical equation?
HCl(aq)+ NaOH(aq)→ NaCl(aq)+ H₂O(l)
Assume that the heat capacity of the solution and calorimeter is 465.4 J/°C.

A)0.139 kJ
B)55.8 kJ
C)2.791 kJ
D)-55.8 kJ
E)2.79 kJ

Question 67

A 500-cm³ sample of 1.0 M NaOH(aq)is added to 500 cm³ of 1.0 M HCl(aq)in a Styrofoam cup,and the solution is quickly stirred.The rise in temperature (ΔT₁)is measured.The experiment is repeated using 100 cm³ of each solution,and the rise in temperature (ΔT₂)is measured.What conclusion can you draw about ΔT₁ and ΔT₂?
HCl(aq)+ NaOH(aq)→ H₂O(l)+ NaCl(aq); ΔH° = -55.8 kJ

A)ΔT₂ is greater than ΔT₁.
B)ΔT₂ is equal to ΔT₁.
C)ΔT₁ is five times as large as ΔT₂.
D)ΔT₁ is less than ΔT₂.
E)ΔT₂ is five times as large as ΔT₁.

Question 68

A 84.8-g piece of silver (s = 0.237 J/(g ∙ °C)),initially at 268.0°C,is added to 128.4 g of a liquid,initially at 24.9°C,in an insulated container.The final temperature of the metal-liquid mixture at equilibrium is 39.6°C.What is the identity of the liquid? Neglect the heat capacity of the container.

A)methanol (s = 2.53 J/(g ∙ °C))
B)ethanol (s = 2.43 J/(g ∙ °C))
C)hexane (s = 2.27 J/(g ∙ °C))
D)water (s = 4.18 J/(g ∙ °C))
E)acetone (s = 2.15 J/(g ∙ °C))

Question 69

How much heat must be applied to a 40.2-g sample of gold (s = 0.129 J/(g ∙ °C))in order to raise its temperature from 28.2°C to 351.5°C?

A)1.82 × 10³ J
B)1.68 × 10³ J
C)1.46 × 10² J
D)1.3 × 10⁴ J
E)4.17 × 10¹ J

Question 70

How much heat is gained by copper when 77.5 g of copper is warmed from 21.4°C to 75.1°C? The specific heat of copper is 0.385 J/(g ∙ °C).

A)6.39 × 10² J
B)28.91 J
C)20.67 J
D)1.6 × 10³ J
E)2.24 × 10³ J

Question 71

When 9.42 g of methane (CH₄)is burned in a bomb calorimeter (heat capacity = 2.677 × 10³ J/°C),the temperature rises from 24.00 to 27.08°C.How much heat is absorbed by the calorimeter?
CH₄(g)+ 2O₂(g)→ CO₂(g)+ 2H₂O(l); ΔH° = -1283.8 kJ

A)745 kJ
B)4.84 × 10³ kJ
C)8.24 kJ
D)753 kJ
E)1.28 × 10³ kJ

Question 72

When 50.0 mL of 1.27 M of HCl(aq)is combined with 50.0 mL of 1.32 M of NaOH(aq)in a coffee-cup calorimeter,the temperature of the solution increases by 8°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

Question 73

A 86.9-g sample of chromium (s = 0.447 J/(g ∙ °C)),initially at 338.33°C,is added to an insulated vessel containing 189.9 g of water (s = 4.18 J/(g ∙ °C)),initially at 16.17°C.At equilibrium,the final temperature of the metal-water mixture is 28.06°C.How much heat was absorbed by the water? The heat capacity of the vessel is 0.220 kJ/°C.

A)9.43 kJ
B)6.82 kJ
C)12 kJ
D)15.2 kJ
E)112 kJ

Question 74

In a bomb calorimeter,reactions are carried out

A)at 1 atm pressure and 0°C.
B)at a constant pressure.
C)at a constant volume.
D)at a constant pressure and 25°C.
E)at 1 atm pressure and 25°C.

Question 75

A bomb calorimeter has a heat capacity of 2.47 kJ/K.When a 0.106-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

Question 76

Given:
Pb(s)+ PbO₂(s)+ 2H₂SO₄(l)→ 2PbSO₄(s)+ 2H₂O(l); ΔH° = -509.2 kJ
SO₃(g)+ H₂O(l)→ H₂SO₄(l); ΔH° = -130.kJ
Determine ΔH° for the following thermochemical equation.
Pb(s)+ PbO₂(s)+ 2SO₃(g)→ 2PbSO₄(s)

A)3.77 × 10³ kJ
B)-521 kJ
C)-3.77 × 10³ kJ
D)-639 kJ
E)-769 kJ

Question 77

Using the following data,calculate the standard enthalpy of reaction for the coal gasification process 2C(s)+ 2H₂O(g)→ CH₄(g)+ CO₂(g).
C(s)+ H₂O(g)→ CO(g)+ H₂(g); ΔH° = +131.3 kJ
CO(g)+ H₂O(g)→ CO₂(g)+ H₂(g); ΔH° = -41.2 kJ
CO(g)+ 3H₂(g)→ CH₄(g)+ H₂O(g); ΔH° = -206.1 kJ

A)-116.0 kJ
B)378.6 kJ
C)+15.3 kJ
D)-157.2 kJ
E)-378.6 kJ

Question 78

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)

Question 79

Combustion of 3.65 g of liquid benzene (C₆H₆)causes a temperature rise of 21.1°C in a constant-pressure calorimeter that has a heat capacity of 7.23 kJ/°C.What is ΔH for the following reaction?
C₆H₆(l)+ O₂(g)→ 6CO₂(g)+ 3H₂O(l)

A)150 kJ/mol
B)41.8 kJ/mol
C)-41.8 kJ/mol
D)-3.27× 10³ kJ/mol
E)152 kJ/mol

Question 80

Which of the following processes will result in the lowest final temperature of the metal-water mixture at equilibrium?

A)the addition of 100 g of silver (s = 0.237 J/(g ∙ °C))at 95°C to 100 mL of water at 25°C in an insulated container
B)the addition of 100 g of cobalt (s = 0.418 J/(g ∙ °C))at 95°C to 100 mL of water at 25°C in an insulated container
C)the addition of 100 g of chromium (s = 0.447 J/(g ∙ °C))at 95°C to 100 mL of water at 25°C in an insulated container
D)the addition of 100 g of copper (s = 0.385 J/(g ∙ °C))at 95°C to 100 mL of water at 25°C in an insulated container
E)the addition of 100 g of gold (s = 0.129 J/(g ∙ °C))at 95°C to 100 mL of water at 25°C in an insulated container