Deck 5: Thermochemistry

Question 1

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

Answer 1

positive, negative

Question 2

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.

Answer 2

gives off heat and does work

Question 3

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

Answer 3

b and c

Question 4

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 5

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 6

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

A)E_k = (1/2)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 7

Of the following, which one is a state function?

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

Question 8

For a given process at constant pressure, ΔH is negative. This means that the process is __________.

A)endothermic
B)equithermic
C)exothermic
D)a state function
E)energy

Question 9

At what velocity (m/s)must a 20.0 g object be moving in order to possess a kinetic energy of 1.00 J?

A)1.00
B)100 × 10²
C)10.0
D)1.00 × 10³
E)50.0

Question 10

A __________ ΔH corresponds to an __________ process.

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

Question 11

The value of ΔE for a system that performs 111 kJ of work on its surroundings and gains 89 kJ of heat is __________ kJ.

A)-111
B)-200
C)200
D)-22
E)22

Question 12

The value of ΔE for a system that performs 13 kJ of work on its surroundings and loses 9 kJ of heat is __________ kJ.

A)22
B)-22
C)-4
D)4
E)-13

Question 13

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

Question 14

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 15

Which of the following statements is false?

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

Question 16

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 compression

Question 17

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 18

A __________ ΔH corresponds to an __________ process.

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

Question 19

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

Question 20

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 21

For the species in the reaction below, ΔH_f° is zero for __________. 2Co (s)+ H₂ (g)+ 8PF₃ (g)→ 2HCo(PF₃)₄ (l)

A)Co (s)
B)H₂ (g)
C)PF₃ (g)
D)HCo(PF₃)₄ (l)
E)both Co(s)and H₂ (g)

Question 22

Under what condition(s)is the enthalpy change of a process equal to the amount of heat transferred into or out of the system? (a)temperature is constant
(b)pressure is constant
(c)volume is constant

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

Question 23

The temperature of a 35.2 g sample of iron increases from 23.7 °C to 29.5 °C. If the specific heat of iron is 0.450 J/g-K, how many joules of heat are absorbed?

A)4.3
B)92
C)0.450
D)1100
E)1.1 x 10³

Question 24

The temperature of a 12.58 g sample of calcium carbonate [CaCO₃ (s)] increases from 23.6 °C to 38.2 °C. If the specific heat of calcium carbonate is 0.82 J/g-K, how many joules of heat are absorbed?

A)0.82
B)5.0
C)7.5
D)410
E)151

Question 25

An 8.29 g sample of calcium carbonate [CaCO₃ (s)] absorbs 50.3 J of heat, upon which the temperature of the sample increases from 21.1 °C to 28.5 °C. What is the specific heat of calcium carbonate?

A).63
B).82
C)1.1
D)2.2
E)4.2

Question 26

The British thermal unit (Btu)is commonly used in engineering applications. A Btu is defined as the amount of heat required to raise the temperature of 1 lb of water by 1 °F. There are __________ joules in one Btu. 1 lb = 453.59 g; °C = (5/9)(°F - 32°); specific heat of H₂O (l)= 4.184 J/g-K.

A)3415
B)60.29
C)1054
D)5.120 × 10^-3
E)Additional information is needed to complete the calculation.

Question 27

The units of 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 28

The units of 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 29

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 30

A sample of calcium carbonate [CaCO₃ (s)] absorbs 45.5 J of heat, upon which the temperature of the sample increases from 21.1 °C to 28.5 °C. If the specific heat of calcium carbonate is 0.82 J/g-K, what is the mass (in grams)of the sample?

A)3.7
B)5.0
C)7.5
D)410
E)5.0 x 10³

Question 31

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 32

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 33

For which one of the following equations is ΔH°_rxn equal to ΔH_f° for the product?

A)Xe (g)+ 2 F₂ (g)→ XeF₄ (g)
B)CH₄ (g)+ 2 Cl₂ (g)→ CH₂ Cl₂ (l)+ 2HCl (g)
C)N₂ (g)+ O₃ (g)→ N₂O₃ (g)
D)2CO (g)+ O₂ (g)→ 2CO₂ (g)
E)C (diamond)+ O₂ (g)→ CO₂ (g)

Question 34

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

Question 35

A 22.44 g sample of iron absorbs 180.8 J of heat, upon which the temperature of the sample increases from 21.1 °C to 39.0 °C. What is the specific heat of iron?

A)0.140
B)0.450
C)0.820
D)0.840
E)0.900

Question 36

Consider the following two reactions: A → 2B ΔH°_rxn = 456.7 kJ/mol
A → C ΔH°_rxn = -22.1kJ/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 37

A sample of iron absorbs 67.5 J of heat, upon which the temperature of the sample increases from 21.5 °C to 28.5 °C. If the specific heat of iron is 0.450 J/g-K, what is the mass (in grams)of the sample?

A)4.3
B)11
C)21
D)1100
E)1.1 x 10³

Question 38

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 39

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 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

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

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

Fuel values of hydrocarbons increase as the H/C atomic ratio increases. Which of the following compounds has the highest fuel value?

A)C₂H₆
B)C₂H₄
C)C₂H₂
D)CH₄
E)C₆H₆

Question 44

The energy released by combustion of 1 g of a substance is called the __________ of the substance.

A)specific heat
B)fuel value
C)nutritional calorie content
D)heat capacity
E)enthalpy

Question 45

For which one of the following reactions is the value of ΔH°_rxn equal to ΔH°_f for the product?

A)H₂O (l)+ 1/2 O₂ (g)→ H₂ O₂ (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 46

For which one of the following reactions is the value of ΔH°_rxn equal to ΔH_f° for the product?

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

Question 47

The most abundant fossil fuel is __________.

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

Question 48

For which one of the following reactions is the value of ΔH°_rxn equal to ΔH_f° for the product?

A)2Ca (s)+ O₂ (g)→ 2CaO (s)
B)C₂H₂ (g)+ H₂ (g)→ C₂H₄ (g)
C)2C (graphite)+ O₂ (g)→ 2CO (g)
D)3Mg (s)+ N₂ (g)→ Mg₃N₂ (s)
E)C (diamond)+ O₂ (g)→ CO₂ (g)

Question 49

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 50

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

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

Question 51

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
B)365
C)978
D)183
E)68.1

Question 52

For which one of the following reactions is the value of ΔH°_rxn equal to ΔH°_f for the product?

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

Question 53

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

A)5.5 x 10⁵
B)5.5 × 10^-5
C)1.1 × 10⁶
D)2.2 × 10⁶
E)2.2 × 10^-6

Question 54

Calculate the kinetic energy in joules of an 80.0 g bullet traveling at 300.0 m/s.

A)3.60 × 10⁶
B)1.20 × 10⁴
C)3.60 × 10³
D)12.0
E)80.0

Question 55

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 56

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

A)1.43 × 10^-3
B)6.00
C)1900
D)454
E)0.0251

Question 57

Of the substances below, the highest fuel value is obtained from __________.

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

Question 58

With reference to enthalpy changes, the term standard conditions means __________. (a)P = 1 atm
(b)some common temperature, usually 298 K
(c)V = 1 L

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

Question 59

Which one of the choices below is not considered a fossil fuel?

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

Question 60

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 61

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 62

The value of ΔH° for the reaction below is -186 kJ. Calculate the heat (kJ)released from the reaction of 25 g of Cl₂. H₂ (g)+ Cl₂ (g)→ 2HCl (g)

A)66
B)5.3 ×
C)33
D)47
E)-186

Question 63

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 64

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 65

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 66

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

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

Question 67

The value of ΔH° for the reaction below is -482 kJ. Calculate the heat (kJ)released to the surroundings when 38.5 g of O₂ (g)reacts with excess CO. 2CO (g)+ O₂ (g)→ 2CO₂ (g)

A)2.65 ×
B)482
C)580.
D)65.7
E)210.

Question 68

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
B)23.2
C)20.8
D)193
E)96.3

Question 69

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

A)0.48
B)62.0
C)1.3 ×
D)32
E)8.3

Question 70

The molar heat capacity of a compound with the formula C₂H₆SO is 88.0 J/mol-K. The specific heat of this substance is __________ J/g-K.

A)88.0
B)1.13
C)4.89
D)6.88 ×
E)-88.0

Question 71

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

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

Question 72

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 5.75 g of CO (g)is formed as shown in the equation?

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

Question 73

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 15.75 g of Ba (s)reacts completely with oxygen to form BaO (s)?

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

Question 74

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? 2 Na₂O₂ (s)+ 2 H₂O (l)→ 4NaOH (s)+ O₂ (g)

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

Question 75

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)+ 3 Cl₂ (g)→ CHCl₃ (l)+ 3HCl (g)

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

Question 76

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
BaO (s)?

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

Question 77

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 ×

Question 78

The value of ΔH° for the reaction below is -72 kJ. __________ kJ of heat are released when 80.9 grams of HBr is formed in this reaction. H₂ (g)+ Br₂ (g)→ 2HBr (g)

A)144
B)72
C)0.44
D)36
E)-72

Question 79

The value of ΔH° for the reaction below is +128.1 kJ: CH₃OH (l)→ CO (g)+ 2 H₂ (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
B)162
C)8.31
D)23.3
E)62.0

Question 80

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

A)162
B)62.0
C)128
D)653
E)326