Deck 5: Thermochemistry

Question 1

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.

Answer 1

The system gains heat and has work done on it by the surroundings.

Question 2

Of the following, which one is a state function?

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

Answer 2

H

Question 3

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

A)E_k = m
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)

Answer 3

Energy lost by the system must be gained by the surroundings.

Question 4

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 5

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 6

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 7

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 8

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 9

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 10

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 11

The reaction 4Al (s) + 3O₂ (g) → 2Al₂O₃ (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 12

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 13

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 14

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 15

A ________ ΔH corresponds to an ________ process.

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

Question 16

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 17

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 18

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 19

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 20

A ________ ΔH corresponds to an ________ process.

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

Question 21

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 22

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 23

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)F₃ (g)
D)Ni(CO)₂(PF₃)₂ (l)
E)both CO (g)and PF₃ (g)

Question 24

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 25

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) → 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 26

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 27

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 28

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 29

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 30

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 31

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

A)Xe (g) + 2F₂ (g) → XeF₄ (g)
B)CH₄ (g) + 2Cl₂ (g) → CH₂Cl₂ (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 32

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 33

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 34

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 ________ Btu in one Joule. 1 lb = 453.59 g; °C = (5/9)(°F - 32°); specific heat of H₂O (l)= 4.184 J/g-K.

A)1056 Btu
B)1.896 × 10^-3 Btu
C)9.278 × 10^-4 Btu
D)5.120 × 10^-3 Btu
E)Additional information is needed to complete the calculation.

Question 35

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 36

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

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

Question 37

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 38

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 39

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

Question 40

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

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

Question 41

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

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

Question 42

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 43

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 44

Calculate the kinetic energy in joules of an automobile weighing 4345 lb and traveling at 75 mph. (1 mile = 1.6093 km, 1lb = 453.59 g).

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 45

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 46

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)? 2C₆H₆ (l) + 15O₂ (g) → 12CO₂ (g) + 6 H₂O (l)

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

Question 47

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 × 10³ kJ
B)482 kJ
C)580. kJ
D)65.7 kJ
E)210. kJ

Question 48

Calculate the kinetic energy in joules of an automobile weighing 2135 lb and traveling at 55 mph. (1 mile = 1.6093 km, 1lb = 453.59 g).

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 49

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 50

The most abundant fossil fuel is ________.

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

Question 51

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 52

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 53

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 54

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 55

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 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 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 58

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 59

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 60

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 61

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

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

Question 62

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

Question 63

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 64

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 65

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

Question 66

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 67

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 68

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 H₂ (g)is formed as shown in the equation?

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

Question 69

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

Question 70

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 71

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) + 2 Fe₃O₄ (s)
Is ________ kJ.

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

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 15.5 g of CH₃OH (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 73

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 74

The molar heat capacity of a compound with the formula C₂H₆ SO 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 × 10³
E)-88.0

Question 75

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 kJ
B)5.3 × 10² kJ
C)33 kJ
D)47 kJ
E)-186 kJ

Question 76

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 77

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 78

The specific heat capacity of lead is 0.13 J/g-K. How much heat (in J)is required to raise the temperature of 15 g 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 79

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 80

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