Deck 5: Thermochemistry

Question 1

The reaction 4Al (s)+ 3O₂ (g)→ 2 Al₂O₃ (s)ΔH° = -3351 kJ
Is ________,and therefore heat is ________ by the reaction.

A)endothermic, released
B)endothermic, absorbed
C)exothermic, released
D)exothermic, absorbed
E)thermoneutral, neither released nor absorbed

Answer 1

exothermic, released

Question 2

Which one of the following is an endothermic process?

A)ice melting
B)water freezing
C)boiling soup
D)Hydrochloric acid and barium hydroxide are mixed at 25 °C: the temperature increases.
E)Both A and C

Answer 2

Both A and C

Question 3

The internal energy can be increased by ________. (a)transferring heat from the surroundings to the system
(b)transferring heat from the system to the surroundings
(c)doing work on the system

A)a only
B)b only
C)c only
D)a and c
E)b and c

Answer 3

a and c

Question 4

The internal energy of a system is always increased by ________.

A)adding heat to the system
B)having the system do work on the surroundings
C)withdrawing heat from the system
D)adding heat to the system and having the system do work on the surroundings
E)a volume decompression

Question 5

A chemical reaction that releases heat to the surroundings is said to be ________ and has a ________ ΔH at constant pressure.

A)endothermic, positive
B)endothermic, negative
C)exothermic, negative
D)exothermic, positive
E)exothermic, neutral

Question 6

A ________ ΔH corresponds to an ________ process.

A)negative, endothermic
B)negative, exothermic
C)positive, exothermic
D)zero, exothermic
E)zero, endothermic

Question 7

The internal energy of a system ________.

A)is the sum of the kinetic energy of all of its components
B)is the sum of the rotational, vibrational, and translational energies of all of its components
C)refers only to the energies of the nuclei of the atoms of the component molecules
D)is the sum of the potential and kinetic energies of the components
E)none of the above

Question 8

Objects can possess energy as ________. (a)endothermic energy
(b)potential energy
(c)kinetic energy

A)a only
B)b only
C)c only
D)a and c
E)b and c

Question 9

Which one of the following statements is true?

A)Enthalpy is an intensive property.
B)The enthalpy change for a reaction is independent of the state of the reactants and products.
C)Enthalpy is a state function.
D)H is the value of q measured under conditions of constant volume.
E)The enthalpy change of a reaction is the reciprocal of the ΔH of the reverse reaction.

Question 10

Which one of the following is an exothermic process?

A)ice melting
B)water evaporating
C)boiling soup
D)condensation of water vapor
E)Ammonium thiocyanate and barium hydroxide are mixed at 25 °C: the temperature drops.

Question 11

Which of the following is a statement of the first law of thermodynamics?

A)E_k = mv²
B)A negative ΔH corresponds to an exothermic process.
C)ΔE = E_final - E_initial
D)Energy lost by the system must be gained by the surroundings.
E)1 cal = 4.184 J (exactly)

Question 12

When ________ is constant,the enthalpy change of a process equal to the amount of heat transferred into or out of the system?

A)temperature
B)volume
C)pressure and volume
D)temperature and volume
E)pressure

Question 13

ΔH for an endothermic process is ________ while ΔH for an exothermic process is ________.

A)zero, positive
B)zero, negative
C)positive, zero
D)negative, positive
E)positive, negative

Question 14

Of the following,which one is a state function?

A)H
B)q
C)w
D)heat
E)none of the above

Question 15

A ________ ΔH corresponds to an ________ process.

A)negative, endothermic
B)positive, exothermic
C)positive, endothermic
D)zero, exothermic
E)zero, endothermic

Question 16

All of the following statements are true except ________.

A)Internal energy is a state function.
B)The enthalpy change for a reaction is equal in magnitude, but opposite in sign, to the enthalpy change for the reverse reaction.
C)The enthalpy change for a reaction depends on the state of the reactants and products.
D)The enthalpy of a reaction is equal to the heat of the reaction.
E)Enthalpy is an intensive property.

Question 17

A chemical reaction that absorbs heat from the surroundings is said to be ________ and has a ________ ΔH at constant pressure.

A)endothermic, positive
B)endothermic, negative
C)exothermic, negative
D)exothermic, positive
E)exothermic, neutral

Question 18

Which one of the following conditions would always result in an increase in the internal energy of a system?

A)The system loses heat and does work on the surroundings.
B)The system gains heat and does work on the surroundings.
C)The system loses heat and has work done on it by the surroundings.
D)The system gains heat and has work done on it by the surroundings.
E)None of the above is correct.

Question 19

When a system ________,ΔE is always negative.

A)absorbs heat and does work
B)gives off heat and does work
C)absorbs heat and has work done on it
D)gives off heat and has work done on it
E)None of the above is always negative.

Question 20

For a given process at constant pressure,w is positive.This means that the process involves ________.

A)work being done by the system on the surroundings
B)work being done by the surroundings on the system
C)no work being done
D)an equal amount of work done on the system and by the system
E)work being done against a vacuum

Question 21

Consider the following two reactions: A → 2B ΔH°_rxn = 456.7 kJ/mol
A → C ΔH°_rxn = -22.1 kJ/mol
Determine the enthalpy change for the process:
2B → C

A)-478.8 kJ/mol
B)-434.6 kJ/mol
C)434.6 kJ/mol
D)478.8 kJ/mol
E)More information is needed to solve the problem.

Question 22

Which of the following is a statement of Hess's law?

A)If a reaction is carried out in a series of steps, the ΔH for the reaction will equal the sum of the enthalpy changes for the individual steps.
B)If a reaction is carried out in a series of steps, the ΔH for the reaction will equal the product of the enthalpy changes for the individual steps.
C)The ΔH for a process in the forward direction is equal in magnitude and opposite in sign to the ΔH for the process in the reverse direction.
D)The ΔH for a process in the forward direction is equal to the ΔH for the process in the reverse direction.
E)The ΔH of a reaction depends on the physical states of the reactants and products.

Question 23

For the following reactions,the ΔH°_rxn is NOT equal to ΔH°_f for the product except for ________.

A)H₂ (g)+ 1/2 O₂ (g)→ H₂O (l)
B)H₂ (g)+ O₂ (g)→ H₂O₂ (l)
C)2C (s, graphite)+ 2H₂ (g)→ C₂H₄ (g)
D)1/2 N₂ (g)+ O₂ (g)→ NO₂ (g)
E)all of the above

Question 24

For the following reactions,the ΔH°_rxn is NOT equal to ΔH°_f for the product except for ________.

A)2Ca (s)+ O₂ (g)→ 2CaO (s)
B)3Mg (s)+ N₂ (g)→ Mg₃N₂ (s)
C)C₂H₂ (g)+ H₂ (g)→ H₄ (g)
D)2C (graphite)+ O₂ (g)→ 2CO (g)
E)C (diamond)+ O₂ (g)→ CO₂ (g)

Question 25

Of the following,ΔH°_f is not zero for ________.

A)O₂ (g)
B)C (graphite)
C)N₂ (g)
D)F₂ (s)
E)Cl₂ (g)

Question 26

All of the following are considered fossil fuels except ________.

A)hydrogen
B)anthracite coal
C)crude oil
D)natural gas
E)petroleum

Question 27

The units of specific heat are ________.

A)K/J or °C/J
B)J/K or J/°C
C)J/g-K or J/g-°C
D)J/mol
E)g-K/J or g-°C/J

Question 28

For the combustion reaction of methane,ΔH°_f is zero for ________. CH₄ (g)+ O₂ (g)→ 2H₂O(g)+ CO₂ (g)

A)O₂ (g)
B)CH₄ (g)
C)CO₂ (g)
D)H₂O (g)
E)Both O₂ (g)and CH₄ (g)

Question 29

For which one of the following reactions is ΔH°_rxn equal to the heat of formation of the product?

A)N₂ (g)+ 3H₂ (g)→ 2NH₃ (g)
B)(1/2)N₂ (g)+ O₂ (g)→ NO₂(g)
C)6C (s)+ 6H (g)→ C₆H₆ (l)
D)P (g)+ 4H (g)+ Br (g)→ PH₄Br (l)
E)12C (g)+ 11H₂ (g)+ 11O (g)→ C₆H₂₂O₁₁ (g)

Question 30

Fuel values of hydrocarbons increase as the ________ increases.

A)C atomic ratio
B)H/C atomic ratio
C)H atomic ratio
D)C/C atomic ratio
E)C/H atomic ratio

Question 31

The units of heat capacity are ________.

A)K/J or °C/J
B)J/K or J/°C
C)J/g-K or J/g-°C
D)J/mol
E)g-K/J or g-°C/J

Question 32

In the reaction below,ΔH°_f is zero for ________. Ni (s)+ 2CO (g)+ 2PF₃ (g)→ Ni(CO)₂(PF₃)₂ (l)

A)Ni (s)
B)CO (g)
C)PF₃ (g)
D)Ni(CO)₂(PF₃)₂ (l)
E)both CO (g)and PF₃ (g)

Question 33

The term Btu which stands for ________ is commonly used in engineering applications.

A)Best thermal unit
B)Bunsen thermal unit
C)British thermal unit
D)Bake thermal unit
E)Brush thermal unit

Question 34

For the following reactions,the ΔH°_rxn is NOT equal to ΔH°_f for the product except for ________.

A)CH₄ (g)+ 2Cl₂ (g)→ CH₂Cl₂ (l)+ 2HCl (g)
B)N₂ (g)+ O₃ (g)→ N₂O₃ (g)
C)Xe (g)+ 2F₂ (g)→ XeF₄ (g)
D)2CO (g)+ O₂ (g)→ 2CO₂ (g)
E)C (diamond)+ O₂ (g)→ CO₂ (g)

Question 35

For the following reactions,the ΔH°_rxn is NOT equal to ΔH°_f for the product except for ________.

A)N₂ (g)+ O₂ (g)→ 2NO (g)
B)2H₂ (g)+ O₂ (g)→ 2H₂O (l)
C)2H₂ (g)+ O₂ (g)→ 2H₂O (g)
D)2C (s, graphite)+ 2H₂(g)→ C₂H₄ (g)
E)H₂O (l)+ 1/2 O₂ (g)→ H₂O₂ (l)

Question 36

________ yields the highest fuel value.

A)hydrogen
B)charcoal
C)bituminous coal
D)natural gas
E)wood

Question 37

The term standard conditions with respect to enthalpy change means ________.

A)1 atm and 0 K
B)1 atm and 1 L
C)1 atm and 298 K
D)1 L and 0 K
E)1 atm and 1 °C

Question 38

For the following reactions,the ΔH°_rxn is NOT equal to ΔH°_f for the product except for ________.

A)H₂O (l)+ 1/2O₂ (g)→ H₂O₂ (l)
B)N₂ (g)+ O₂ (g)→ 2NO (g)
C)2H₂ (g)+ O₂ (g)→ 2H₂O (l)
D)2H₂ (g)+ O₂ (g)→ 2H₂O (g)
E)none of the above

Question 39

The energy released by combustion of ________ of a substance is called the fuel value of the substance.

A)1 kJ
B)1 kg
C)1 lb
D)1 J
E)1 g

Question 40

Of the following,ΔH°_f is not zero for ________.

A)Sc (g)
B)Si (s)
C)P₄ (s, white)
D)Br₂ (l)
E)Ca (s)

Question 41

The kinetic energy of a 10.3 g golf ball traveling at 48.0 m/s is ________ J.

A)1.20 × 10³
B)66
C)11.9
D)1.3 × 10²
E)23.7

Question 42

The kinetic energy of a 23.2-g object moving at a speed of 81.9 km/hr is ________ J.

A)1900
B)77.8
C)145
D)1.43 × 10^-3
E)6.00

Question 43

What is the kinetic energy of a 55.2 g object moving at 135 m/s.

A)503 J
B)5.03 × 10⁵ J
C)1.01 × 10³ J
D)3.73 J
E)3.73 × 10³ J

Question 44

Carbon monoxide and oxygen gas react to form carbon dioxide.How much heat is released when 89.5 grams of O₂ (g)reacts with excess CO? ΔH° = -482 kJ.

A)1.35 × 10^{3 kJ}
B)2.70 × 10³ kJ
C)1.35 × 10^-3 kJ
D)674 kJ
E)4.31 × 10⁴ kJ

Question 45

Calculate the kinetic energy in joules of an automobile weighing 4345 lb and traveling at 75 mph.

A)5.5 × 10^{5 J}
B)5.5 × 10^-5 J
C)1.1 × 10⁶ J
D)2.2 × 10⁶ J
E)2.2 × 10^-6 J

Question 46

The kinetic energy of a 7.3 kg steel ball traveling at 18.0 m/s is ________ J.

A)1.2 × 10³
B)66
C)2.4 × 10³
D)1.3 × 10²
E)7.3

Question 47

The value of ΔH° for the reaction below is -6535 kJ. ________ kJ of heat are released in the combustion of 16.0 g of (l)?
2C₆H₆ (l)+ 15O₂ (g)→ 12CO₂ (g)+ 6H₂O (l)

A)1.34 × 10³
B)5.23 × 10⁴
C)669
D)2.68 × 10³
E)-6535

Question 48

Calculate the kinetic energy in joules of a 150 lb jogger (68.1 kg)traveling at 12.0 mile/hr (5.36 m/s).

A)1.96 × 10³ J
B)365 J
C)978 J
D)183 J
E)68.1 J

Question 49

Calculate the kinetic energy in joules of an automobile weighing 2135 lb and traveling at 55 mph.

A)1.2 × 10⁴ J
B)2.9 × 10⁵ J
C)5.9 × 10⁵ J
D)3.2 × 10⁶ J
E)3.2 × 10^-6 J

Question 50

The ΔE of a system that absorbs 12.4 J of heat and does 4.2 J of work on the surroundings is ________ J.

A)16.6
B)12.4
C)4.2
D)-16.6
E)8.2

Question 51

The change in the internal energy of a system that absorbs 2,500 J of heat and that does 7,655 J of work on the surroundings is ________ J.

A)10,155
B)5,155
C)-5,155
D)-10,155
E)1.91 × 10⁷

Question 52

A 100-watt electric incandescent light bulb consumes ________ J of energy in 24 hours.[1 Watt (W)= 1 J/sec]

A)2.40 × 10³
B)8.64 × 10³
C)4.17
D)2.10 × 10³
E)8.64 × 10⁶

Question 53

The value of ΔH° for the reaction below is -790 kJ.The enthalpy change accompanying the reaction of 0.95 g of S is ________ kJ. 2S (s)+ 3O₂ (g)→ 2SO₃ (g)

A)23
B)-23
C)-12
D)12
E)-790

Question 54

Calculate the kinetic energy in J of an electron moving at 6.00 × 10⁶ m/s.The mass of an electron is 9.11 × 10^-28 g.

A)4.98 × 10^-48 J
B)3.28 × 10^-14 J
C)1.64 × 10^-17 J
D)2.49 × 10^-48 J
E)6.56 × 10^-14 J

Question 55

What is the kinetic energy of a 145 g baseball traveling at 89.9 mi/hr?

A)(^{1.17 × 105 J})
B)2.91 J
C)234 J
D)5.83
E)117 J

Question 56

The value of ΔH° for the reaction below is -126 kJ. ________ kj are released when 2.00 mol of NaOH is formed in the reaction?
2Na₂O₂ (s)+ 2H₂O (l)→ 4NaOH (s)+ O₂ (g)

A)252
B)63
C)3.9
D)7.8
E)-126

Question 57

The change in the internal energy of a system that releases 2,500 J of heat and that does 7,655 J of work on the surroundings is ________ J.

A)-10,155
B)-5,155
C)-1.91 × 10⁷
D)10,155
E)5,155

Question 58

Hydrogen gas and bromine gas react to form hydrogen bromide gas.How much heat (kJ)is released when 155 grams of HBr is formed in this reaction? ΔH° = -72 kJ.

A)137
B)69
C)-69
D)-137
E)1.12 × 10⁵

Question 59

The ΔE of a system that releases 12.4 J of heat and does 4.2 J of work on the surroundings is ________ J.

A)16.6
B)12.4
C)4.2
D)-16.6
E)-8.2

Question 60

The most abundant fossil fuel is ________.

A)natural gas
B)petroleum
C)coal
D)uranium
E)hydrogen

Question 61

CH₃OH (l)decomposes into carbon monoxide and hydrogen gas in the presence of heat.How much heat is consumed when 5.75 g of CO (g)is formed? ΔH° = +128.1 kJ.

A)26.3 kJ
B)23.3 kJ
C)62.0 kJ
D)162 kJ
E)8.3 kJ

Question 62

How much heat is released when 29.5 grams of Cl₂ (g)reacts with excess hydrogen?
H₂ (g)+ Cl₂ (g)→ 2HCl (g)ΔH° = -186 kJ.

A)186 kJ
B)310 kJ
C)-77.4 kJ
D)-186 kJ
E)77.4 kJ

Question 63

The molar heat capacity of an unknown substance is 92.1 J/mol-K.If the unknown has a molar mass of 118 g/mol,what is the specific heat (J/g-K)of this substance?

A)1.28
B)-92.1
C)1.09 × 10⁴
D)0.781
E)92.1

Question 64

Given the following reactions 2S (s)+ 3O₂ (g)→ 2SO₃ (g)ΔH = -790 kJ
S (s)+ O₂ (g)→ SO₂(g)ΔH = -297 kJ
The enthalpy of the reaction in which sulfur dioxide is oxidized to sulfur trioxide
2SO₂ (g)+ O₂ (g)→ 2SO₃ (g)
Is ________ kJ.

A)196
B)-196
C)1087
D)-1384
E)-543

Question 65

ΔH for the reaction IF₅ (g)→ IF₃ (g)+ F₂ (g)
Is ________ kJ,give the data below.
IF (g)+ F₂ (g)→ IF₃ (g)ΔH = -390 kJ
IF (g)+ 2F₂ (g)→ IF₅ (g)ΔH = -745 kJ

A)+355
B)-1135
C)+1135
D)+35
E)-35

Question 66

The value of ΔH° for the reaction below is +128.1 kJ: CH₃OH (l)→ CO (g)+ 2H₂ (g)
How much heat is consumed when 87.1 g of hydrogen gas is formed?

A)2.76 × 10³ kJ
B)5.52 × 10³ kJ
C)-5.52 × 10³ kJ
D)-2.76 × 10³ kJ
E)-128.1 kJ

Question 67

How many kJ of heat are released when 15.75 g of Ba (s)reacts completely with oxygen gas to form BaO (s)? ΔH° = -1107 kJ.

A)63.5 kJ
B)20.8 kJ
C)114 kJ
D)70.3 kJ
E)35.1 kJ

Question 68

The temperature of a 15-g sample of lead metal increases from 22 °C to 37 °C upon the addition of 29.0 J of heat.The specific heat capacity of the lead is ________ J/g-K.

A)7.8
B)1.9
C)29
D)0.13
E)-29

Question 69

The value of ΔH° for the reaction below is -336 kJ.Calculate the heat (kJ)released to the surroundings when 23.0 g of HCl is formed. CH₄ (g)+ 3Cl₂ (g)→ CHCl₃ (l)+ 3HCl (g)

A)177 kJ
B)2.57 × 10³ kJ
C)70.7 kJ
D)211 kJ
E)-336 kJ

Question 70

Given the following reactions Fe₂O₃ (s)+ 3CO (s)→ 2Fe (s)+ 3CO₂ (g)ΔH = -28.0 kJ
3Fe (s)+ 4CO₂(s)→ 4CO (g)+ Fe₃O₄(s)ΔH = +12.5 kJ
The enthalpy of the reaction of Fe₂O₃ with CO
3Fe₂O₃ (s)+ CO (g)→ CO₂ (g)+ 2Fe₃O₄ (s)
Is ________ kJ.

A)-59.0
B)40.5
C)-15.5
D)-109
E)+109

Question 71

The enthalpy change for the following reaction is -483.6 kJ: 2H₂ (g)+ O₂ (g)→ 2H₂O (g)
Therefore,the enthalpy change for the following reaction is ________ kJ.
4H₂ (g)+ 2O₂ (g)→ 4H₂O (g)

A)-483.6
B)-967.2
C)2.34 × 10⁵
D)483.6
E)967.2

Question 72

The specific heat of liquid bromine is 0.226 J/g-K. How much heat (J)is required to raise the temperature of 10.0 mL of bromine from 25.00 °C to 27.30 °C? The density of liquid bromine: 3.12 g/mL.

A)5.20 J
B)16.2 J
C)300 J
D)32.4 J
E)10.4 J

Question 73

The value of ΔH° for the reaction below is +128.1 kJ: CH₃OH (l)→ CO (g)+ 2H₂ (g)
How many kJ of heat are consumed when 15.5 g of C OH (l)decomposes as shown in the equation?

A)0.48 kJ
B)62.0 kJ
C)1.3 × 10² kJ
D)32 kJ
E)8.3 kJ

Question 74

Given the following reactions N₂ (g)+ 2O₂ (g)→ 2NO₂ (g)ΔH = 66.4 kJ
2NO (g)+ O₂ (g)→ 2NO₂ (g)ΔH = -114.2 kJ
The enthalpy of the reaction of the nitrogen to produce nitric oxide
N₂ (g)+ O₂ (g)→ 2NO (g)
Is ________ kJ.

A)180.6
B)-47.8
C)47.8
D)90.3
E)-180.6

Question 75

Given the following reactions 2NO → N₂ + O₂ ΔH = -180 kJ
2NO + O₂ → 2NO₂ ΔH = -112 kJ
The enthalpy of the reaction of nitrogen with oxygen to produce nitrogen dioxide
N₂ + 2O₂ → 2NO₂
Is ________ kJ.

A)68
B)-68
C)-292
D)292
E)-146

Question 76

What is the molar heat capacity (in J/mol-K)of liquid bromine? The specific heat of liquid bromine is 0.226 J/g-K.

A)36.1 J/mol-K
B)707 J/mol-K
C)18.1 J/mol-K
D)9.05 J/mol-K
E)0.226 J/mol-K

Question 77

The value of ΔH° for the reaction below is -1107 kJ: 2Ba (s)+ O₂ (g)→ 2BaO (s)
How many kJ of heat are released when 5.75 g of BaO (s)is produced?

A)56.9 kJ
B)23.2 kJ
C)20.8 kJ
D)193 kJ
E)96.3 kJ

Question 78

The value of ΔH° for the reaction below is -1107 kJ: 2Ba (s)+ O₂ (g)→ 2BaO (s)
How many kJ of heat are released when 5.75 g of Ba (s)reacts completely with oxygen to form

A)96.3 kJ
B)26.3 kJ
C)46.4 kJ
D)23.2 kJ
E)193 kJ

Question 79

The specific heat capacity of lead is 0.13 J/g-K.How much heat (in J)is required to raise the temperature of of lead from 22 °C to 37 °C?

A)2.0 J
B)-0.13 J
C)5.8 × 10^-4 J
D)29 J
E)0.13 J

Question 80

The value of ΔH° for the reaction below is +128.1 kJ: CH₃OH (l)→ CO (g)+ 2H₂ (g)
How many kJ of heat are consumed when 5.10 g of CO (g)is formed as shown in the equation?

A)0.182 kJ
B)162 kJ
C)8.31 kJ
D)23.3 kJ
E)62.0 kJ