Deck 19: Chemical Thermodynamics

Question 1

For a given reaction, OH = +35.5 kJ/mol and OS = +83.6 J/K- mol. The reaction is spontaneous
) Assume that OH and OS do not vary with temperature.

A) at all temperatures
B) at T < 425 K
C) at T < 298 K
D) at T > 425 K
E) at T > 298 K

Answer 1

at T > 425 K

Question 2

OS is positive for the reaction _.

A) 2SO₃ (g) - 2SO₂ (g) + O₂ (g)
B) H₂O (l) -H₂O (s)
C) CaO (s) + CO₂ (g) -CaCO₃ (s)
D) Ag⁺ (aq) + Cl^- (aq) - AgCl (s)
E) N₂ (g) + 3H₂ (g) - 2NH₃ (g)

Answer 2

2SO₃ (g) - 2SO₂ (g) + O₂ (g)

Question 3

The equilibrium position corresponds to which letter on the graph of G vs f (course of reaction) below?

A) A
B) B
C) C
D) D
E) E

Answer 3

C

Question 4

In the Haber process, ammonia is synthesized from nitrogen and hydrogen:

ΔG° at 298 ^oK for this reaction is - 33.3 kJ/mol. The value of ΔG at 298 K for a reaction mixture that consists of 1.9 atm N₂, 1.6 atm H₂, and 0.65 atm NH₃ is _ .

A) - 104.5
B) - 3.86 × 10³
C) - 40.5
D) - 7.25 × 10³
E) - 1.8

Question 5

A reaction that is spontaneous as written .

A) is very rapid
B) is very slow
C) will proceed without outside intervention
D) is also spontaneous in the reverse direction
E) has an equilibrium position that lies far to the left

Question 6

ΔS is negative for the reaction .

A) 2C (s) + O₂ (g) - 2CO₂ (g)
B) 2SO₂ (g) + O₂ (g) - 2SO₃ (g)
C) H₂O (l) -H₂O (g)
D) NH₄Cl (s) - NH₃ (g) + HCl (g)
E) PbCl₂ (s) - Pb²⁺ (aq) + 2Cl^- (aq)

Question 7

The value of ΔG° at 100.0 °C for the formation of calcium chloride from its constituent elements:

Is kJ/mol. At 25.0 ^oC for this reaction, ΔH° is - 795.8 kJ/mol, ΔG° is - 748.1 kJ/mol, and
ΔS° is - 159.8 J/K.

A) 5.88 × 10⁴
B) - 855.4
C) 1.52 × 10⁴
D) - 779.8
E) - 736.2

Question 8

With thermodynamics, one cannot determine .

A) the speed of a reaction
B) the extent of a reaction
C) the value of the equilibrium constant
D) the direction of a spontaneous reaction
E) the temperature at which a reaction will be spontaneous

Question 9

The entropy of the universe is .

A) constant
B) continually increasing
C) continually decreasing
D) the same as the energy, E
E) zero

Question 10

The thermodynamic quantity that expresses the degree of disorder in a system is _ _.

A) heat flow
B) enthalpy
C) entropy
D) bond energy
E) internal energy

Question 11

For the reaction ΔH° is +137 kJ/mol and ΔS° is +120 J/K · mol. This reaction is .

A) spontaneous only at high temperature
B) spontaneous at all temperatures
C) spontaneous only at low temperature
D) nonspontaneous at all temperatures

Question 12

A common name for methanol (CH₃OH) is wood alcohol. The normal boiling point of methanol is 64.7 °C and the molar enthalpy of vaporization if 71.8 kJ/mol. The value of ΔS when 2.15 mol of CH₃OH (l) vaporizes at 64.7 °C is J/K.

A) 5.21 × 10⁷
B) 0.457
C) 457
D) 2.39
E) 2.39 × 10³

Question 13

The standard Gibbs free energy of formation of is zero.
(a) H₂O (l)
(b) Na (s)
(c) H₂ (g)

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

Question 14

A system that doesn't exchange matter or energy with its surroundings is called an system.

A) isotonic
B) adiabatic
C) isothermal
D) isobaric
E) isolated

Question 15

Of the following, only _ is not a state function.

A) H
B) T
C) S
D) q
E) E

Question 16

Consider the reaction:

Given the following table of thermodynamic data,
Determine the temperature (in °C) above which the reaction is nonspontaneous.

A) This reaction is spontaneous at all temperatures.
B) 618.1
C) 1235
D) 345.1
E) 432.8

Question 17

Given the following table of thermodynamic data,

Complete the following sentence. The vaporization of TiCl₄ is _ .

A) nonspontaneous at low temperature and spontaneous at high temperature
B) spontaneous at low temperature and nonspontaneous at high temperature
C) spontaneous at all temperatures
D) nonspontaneous at all temperatures
E) not enough information given to draw a conclusion

Question 18

A reversible process is one that _ _.

A) must be carried out at high temperature
B) can be reversed with no net change in either system or surroundings
C) must be carried out at low temperature
D) happens spontaneously
E) is spontaneous in both directions

Question 19

Which reaction produces an increase in the entropy of the system?

A) H₂ (g) + Cl₂ (g) - 2 HCl (g)
B) Ag⁺ (aq) + Cl^- (aq) - AgCl (s)
C) N₂ (g) + 3 H₂ (g) - 2 NH₃ (g)
D) H₂O (l) -H₂O (s)
E) CO₂ (s) - CO₂ (g)

Question 20

The second law of thermodynamics states that .

A) ΔH°_rxn = 3 nΔH°_f (products) - 3 mΔH°_f (reactants)
B) for any spontaneous process, the entropy of the universe increases
C) ΔS = q_rev/T at constant temperature
D) ΔE = q + w
E) the entropy of a pure crystalline substance is zero at absolute zero

Question 21

A reaction that is not spontaneous at low temperature can become spontaneous at high temperature if OH is and OS is _ .

A) +, +
B) - , -
C) +, -
D) - , +
E) +, 0

Question 22

Which one of the following is always positive when a spontaneous process occurs?

A) ΔH universe
B) ΔS universe
C) ΔS surroundings
D) ΔH surroundings
E) ΔS system

Question 23

The standard Gibbs free energy of formation of is zero.
(a) H₂O (l)
(b) O (g)
(c) H₂ (g)

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

Question 24

Which one of the following statements is true about the equilibrium constant for a reaction if ΔG° for the reaction is negative?

A) K = 1
B) K > 1
C) K < 1
D) K = 0
E) More information is needed.

Question 25

Given the following table of thermodynamic data,

Complete the following sentence. The vaporization of PCl₃ (l) is .

A) spontaneous at low temperature and nonspontaneous at high temperature
B) nonspontaneous at all temperatures
C) spontaneous at all temperatures
D) nonspontaneous at low temperature and spontaneous at high temperature
E) not enough information given to draw a conclusion

Question 26

For an isothermal process, OS = .

A) Tq_rev
B) q
C) q_rev/T
D) q + w
E) qrev

Question 27

When a system is at equilibrium, _.

A) the process is not spontaneous in either direction
B) the forward and the reverse processes are both spontaneous
C) both forward and reverse processes have stopped
D) the reverse process is spontaneous but the forward process is not
E) the forward process is spontaneous but the reverse process is not

Question 28

For a reaction to be spontaneous under standard conditions at all temperatures, the signs of ΔH° and ΔS° must be _ _ and , respectively.

A) +, +
B) +, -
C) - , +
D) - , -
E) +, 0

Question 29

Which one of the following correctly indicates the relationship between the entropy of a system and the number of different arrangements, W, in the system?

A) S = k lnW
B)
C)
D) S = kW
E) S = Wk

Question 30

The value of ΔG° at 141.0 °C for the formation of phosphorous trichloride from its constituent elements, is kJ/mol. At 25.0 ^oC for this reaction, ΔH° is - 720.5 kJ/mol, ΔG° is - 642.9 kJ/mol, and
ΔS° is - 263.7 J/K.

A) - 611.3
B) - 829.7
C) 3.65 × 10⁴
D) 1.08 × 10⁵
E) - 683.3

Question 31

The first law of thermodynamics can be given as .

A) for any spontaneous process, the entropy of the universe increases
B) ΔS = q_rev/T at constant temperature
C) ΔE = q + w
D) the entropy of a pure crystalline substance at absolute zero is zero
E) ΔH°_rxn = _ΣnΔH°_f (products) - _ΣmΔH°_f (reactants)

Question 32

OS is positive for the reaction _.

A) 2Hg (l) + O₂ (g) - 2HgO (s)
B) BaF₂ (s) - Ba²⁺ (aq) + 2F^- (aq)
C) 2H₂ (g) + O₂ (g) - 2H₂O (g)
D) 2NO₂ (g) - N₂O₄ (g)
E) CO₂ (g) -CO₂ (s)

Question 33

The value of ΔG° at 100.0 °C for the oxidation of solid elemental sulfur to gaseous sulfur dioxide,
S (s,rhombic) + O₂ (g) →SO₂ (g)
Is kJ/mol. At 25.0 ^oC for this reaction, ΔH° is - 269.9 kJ/mol, ΔG° is - 300.4 kJ/mol, and
ΔS° is +11.6 J/K.

A) - 274.2
B) - 1,430
C) - 4,598
D) - 271.1
E) - 265.6

Question 34

Of the following, the entropy of gaseous _ is the largest at 25 °C and 1 atm.

A) C₂H₄
B) C₂H₂
C) C₂H₆
D) H₂
E) CH₄

Question 35

Which one of the following processes produces a decrease in the entropy of the system?

A) boiling water to form steam
B) melting ice to form water
C) dissolution of solid KCl in water
D) mixing of two gases into one container
E) freezing water to form ice

Question 36

For a given reaction, ΔH = - 19.9 kJ/mol and ΔS = - 55.5 J/K- mol. The reaction will have ΔG = 0 at------K. Assume that ΔH and ΔS do not vary with temperature.

A) 359
B) 2789
C) 0.359
D) 2.79
E) 298

Question 37

If ΔG° for a reaction is greater than zero, then .

A) K = 1
B) K = 0
C) K < 1
D) K > 1
E) More information is needed.

Question 38

Of the following, the entropy of is the largest.

A) HCl (g)
B) HCl (s)
C) HCl (l)
D) HBr (g)
E) HI (g)

Question 39

Which reaction produces a decrease in the entropy of the system?

A) 2C (s) + O₂ (g) - 2CO (g)
B) CO₂ (s) -CO₂ (g)
C) H₂O (l) -H₂O (g)
D) 2H₂ (g) + O₂ (g) - 2H₂O (l)
E) CaCO₃ (s) - CaO (s) + CO₂ (g)

Question 40

Phosphorous and chlorine gases combine to produce phosphorous trichloride:

ΔG° at 298 ^oK for this reaction is - 642.9 kJ/mol. The value of ΔG at 298 K for a reaction mixture that consists of 1.5 atm P₂, 1.6 atm Cl₂, and 0.65 atm PCl₃ is _ .

A) - 7.28 × 10³
B) - 3.88 × 10³
C) - 649.5
D) - 44.2
E) - 708.4

Question 41

Use the table below to answer the questions that follow.
Thermodynamic Quantities for Selected Substances at 298.15 K (25°C)
The value of ΔG°at 25 °C for the decomposition of phosphorous trichloride into its constituent elements, is kJ/mol.

A) +642.9
B) - 373.3
C) - 539.2
D) - 642.9
E) +539.2

Question 42

Find the temperature above which a reaction with a OH of 53 .00 kJ/mol and a OS of 100.0 J/K·mol becomes spontaneous.

Question 43

Use the table below to answer the questions that follow.
Thermodynamic Quantities for Selected Substances at 298.15 K (25°C)
The combustion of acetylene in the presence of excess oxygen yields carbon dioxide
The value of ΔS^o for this reaction is J/K.

A) +432.4
B) +689.3
C) - 122.3
D) +122.3
E) - 432.4

Question 44

Use the table below to answer the questions that follow.
Thermodynamic Quantities for Selected Substances at 298.15 K (25°C)
The value of ΔH° for the decomposition of phosphorous trichloride into its constituent elements, is kJ/mol.

A) - 288.1
B) - 720.5
C) +720.5
D) +288.1
E) +576.2

Question 45

Calculate OG^○(in kJ/mol) for the following reaction at 1 atm and 25^○C:
OH_f^○C₂H₆ (g) = - 84.7 kJ/mol; S^○C₂H₆ (g) = 229.5 J/K · mol; OH_f^○CO₂ (g) = - 393.5
kJ/mol; S^○CO₂ (g) = 213.6 J/K · mol; OH_f^○H₂O (l) = - 285.8 kJ/mol; S^○H₂O (l) = 69.9 J/K ·
mol

Question 46

Use the table below to answer the questions that follow.
Thermodynamic Quantities for Selected Substances at 298.15 K (25°C)
The value of ΔH° for the oxidation of solid elemental sulfur to gaseous sulfur trioxide, is kJ/mol.

A) - 395.2
B) +395.2
C) - 790.4
D) +105.1
E) +790.4

Question 47

Use the table below to answer the questions that follow.
Thermodynamic Quantities for Selected Substances at 298.15 K (25°C)
The value of ΔG° at 25 °C for the formation of POCl₃ from its constituent elements, is kJ/mol.

A) - 606.2
B) - 1,005
C) +606.2
D) - 1,109
E) +1,109

Question 48

Use the table below to answer the questions that follow.
Thermodynamic Quantities for Selected Substances at 298.15 K (25°C)
The value of ΔH° for the decomposition of POCl₃ into its constituent elements, is kJ/mol.

A) - 940.1
B) +940.1
C) - 1,228.7
D) +1,228.7
E) +0.00

Question 49

Calculate OG^o (in kJ/mol) for the following reaction at 1 atm and 25^○C:
OG_f^○C₂H₆ (g) = - 32.89 kJ/mol; OG_f^○CO₂ (g) = - 394.4 kJ/mol; OG_f^○H₂O (l) = - 237.2
kJ/mol

Question 50

Use the table below to answer the questions that follow.
Thermodynamic Quantities for Selected Substances at 298.15 K (25°C)
The value of ΔS° for the formation of phosphorous trichloride from its constituent elements, is J/K.

A) +129.4
B) +311.7
C) - 263.7
D) - 129.4
E) - 311.7

Question 51

For the reaction ΔH° = 131.3 kJ/mol andΔS° = 133.6 J/K · mol at 298 K. At temperatures greater than _°C this reaction is spontaneous under standard conditions.

A) 710
B) 983
C) 325
D) 273
E) 552

Question 52

Use the table below to answer the questions that follow.
Thermodynamic Quantities for Selected Substances at 298.15 K (25°C)
The value of ΔS° for the oxidation of solid elemental sulfur to gaseous sulfur trioxide, is J/K.

A) - 166.4
B) +493.1
C) - 19.3
D) - 493.1
E) +19.3

Question 53

Consider a pure crystalline solid that is heated from absolute zero to a temperature above the boiling point of the liquid. Which of the following processes produces the greatest increase in the entropy of the substance?

A) melting the solid
B) heating the solid
C) vaporizing the liquid
D) heating the gas
E) heating the liquid

Question 54

Consider the reaction:

Given the following table of thermodynamic data,
Determine the temperature (in °C) above which the reaction is nonspontaneous under standard conditions.

A) 1641
B) 432.8
C) 1235
D) 150.5
E) 133.0

Question 55

Use the table below to answer the questions that follow.
Thermodynamic Quantities for Selected Substances at 298.15 K (25°C)
The value of ΔH° for the oxidation of solid elemental sulfur to gaseous sulfur dioxide, is kJ/mol.

A) - 269.9
B) +11.6
C) - 11.6
D) +269.9
E) +0.00

Question 56

Calculate OG^○for the autoionization of water at 25^○C. K_w = 1.0 × 10^{- 14}

Question 57

Use the table below to answer the questions that follow.
Thermodynamic Quantities for Selected Substances at 298.15 K (25°C)
The value of ΔH° for the formation of POCl₃ from its constituent elements, is kJ/mol.

A) - 686.5
B) +1228.7
C) +686.5
D) - 1228.7
E) - 397.7

Question 58

Which one of the following processes produces a decrease of the entropy of the system?

A) dissolving sodium chloride in water
B) sublimation of naphthalene
C) dissolving oxygen in water
D) explosion of nitroglycerine
E) boiling of alcohol

Question 59

Consider the reaction:

Given the following table of thermodynamic data,
Determine the temperature (in °C) above which the reaction is nonspontaneous.

A) 756.3
B) 2439
C) This reaction is spontaneous at all temperatures.
D) 618.1
E) 1235

Question 60

Find the temperature above which a reaction with a OH of 123 .0 kJ/mol and a OS of 90.00 J/K·mol becomes spontaneous.

Question 61

Use the table below to answer the questions that follow.
Thermodynamic Quantities for Selected Substances at 298.15 K (25°C)
The value of ΔG° at 25 °C for the oxidation of solid elemental sulfur to gaseous sulfur trioxide, is kJ/mol.

A) +370.4
B) - 740.8
C) +740.8
D) +185.2
E) - 370.4

Question 62

Use the table below to answer the questions that follow.
Thermodynamic Quantities for Selected Substances at 298.15 K (25°C)
The value of ΔS° for the catalytic hydrogenation of acetylene to ethane, is J/K.

A) +28.7
B) +232.5
C) - 232.5
D) +440.9
E) - 76.0

Question 63

Use the table below to answer the questions that follow.
Thermodynamic Quantities for Selected Substances at 298.15 K (25°C)
The value of ΔS° for the decomposition of gaseous sulfur trioxide to solid elemental sulfur and gaseous oxygen, is J/K.

A) - 19.3
B) +493.1
C) +19.3
D) +166.4
E) - 493.1

Question 64

Use the table below to answer the questions that follow.
Thermodynamic Quantities for Selected Substances at 298.15 K (25°C)
The combustion of ethene in the presence of excess oxygen yields carbon dioxide and water:

The value of OS^o for this reaction is J/K.

A) - 347.6
B) +140.9
C) - 140.9
D) +347.6
E) - 267.4

Question 65

Use the table below to answer the questions that follow.
Thermodynamic Quantities for Selected Substances at 298.15 K (25°C)
The combustion of hydrogen in the presence of excess oxygen yields water:

The value of OS^o for this reaction is J/K.

A) +265.7
B) +405.5
C) - 405.5
D) - 265.7
E) - 326.3

Question 66

Use the table below to answer the questions that follow.
Thermodynamic Quantities for Selected Substances at 298.15 K (25°C)
The value of ΔS° for the decomposition of calcium chloride into its constituent elements, is J/K.

A) +159.8
B) +104.6
C) - 159.8
D) - 104.6
E) +369.0

Question 67

Use the table below to answer the questions that follow.
Thermodynamic Quantities for Selected Substances at 298.15 K (25°C)
The value of ΔH° for the decomposition of calcium chloride into its constituent elements, is kJ/mol.

A) - 795.8
B) +397.9
C) - 0.00
D) +795.8
E) - 397.9

Question 68

Use the table below to answer the questions that follow.
Thermodynamic Quantities for Selected Substances at 298.15 K (25°C)
The value of ΔG° at 25 °C for the oxidation of solid elemental sulfur to gaseous sulfur dioxide, is kJ/mol.

A) - 300.4
B) +300.4
C) +269.9
D) - 269.9
E) +395.2

Question 69

Use the table below to answer the questions that follow.
Thermodynamic Quantities for Selected Substances at 298.15 K (25°C)
The value of ΔS° for the decomposition of gaseous sulfur dioxide to solid elemental sulfur and gaseous oxygen, is J/K.

A) +11.6
B) - 11.6
C) - 248.5
D) +485.4
E) +248.5

Question 70

Use the table below to answer the questions that follow.
Thermodynamic Quantities for Selected Substances at 298.15 K (25°C)
Consider the reaction:

Given the following table of thermodynamic data at 298 ^oK:

The value of K for the reaction at 25 °C is .

A) 1.8 × 10⁴
B) 1.9 × 10^{- 10}
C) 5.4 × 10⁹
D) 810
E) 3.7 × 10¹⁰

Question 71

Use the table below to answer the questions that follow.
Thermodynamic Quantities for Selected Substances at 298.15 K (25°C)
The value of ΔH° for the decomposition of gaseous sulfur trioxide to its component elements, is kJ/mol.

A) +790.4
B) +395.2
C) +105.1
D) - 395.2
E) - 790.4

Question 72

Use the table below to answer the questions that follow.
Thermodynamic Quantities for Selected Substances at 298.15 K (25°C)
The value of ΔS° for the oxidation of carbon to carbon monoxide, 2C (s, graphite) + O₂ (g) -2CO (g)
Is J/K. Carbon monoxide is produced in the combustion of carbon with limited oxygen.

A) +408.6
B) +395.8
C) - 408.6
D) +179.4
E) - 12.8

Question 73

Use the table below to answer the questions that follow.
Thermodynamic Quantities for Selected Substances at 298.15 K (25°C)
The value of ΔS° for the catalytic hydrogenation of acetylene
Is J/K.

A) +550.8
B) +18.6
C) - 18.6
D) +112.0
E) - 112.0

Question 74

Use the table below to answer the questions that follow.
Thermodynamic Quantities for Selected Substances at 298.15 K (25°C)
The value of OH° for the formation of phosphorous trichloride from its constituent elements, is kJ/mol

A) - 720.5
B) +432.4
C) - 288.1
D) - 432.4
E) +720.5

Question 75

Use the table below to answer the questions that follow.
Thermodynamic Quantities for Selected Substances at 298.15 K (25°C)
The value of ΔG° at 25 ^oC for the decomposition of gaseous sulfur trioxide to solid elemental sulfur and gaseous oxygen, is kJ/mol.

A) +740.8
B) - 740.8
C) - 370.4
D) +370.4
E) +185.2

Question 76

Use the table below to answer the questions that follow.
Thermodynamic Quantities for Selected Substances at 298.15 K (25°C)
The value of OS° for the formation of POCl₃ from its constituent elements, is J/K.

A) - 321
B) - 771
C) +321
D) +771
E) - 442

Question 77

Use the table below to answer the questions that follow.
Thermodynamic Quantities for Selected Substances at 298.15 K (25°C)
The value of ΔS° for the reaction
2C (s, diamond) + O₂ (g) - 2CO (g) is J/K.

A) +9.5
B) - 195.7
C) - 9.5
D) - 185.9
E) +185.9

Question 78

Use the table below to answer the questions that follow.
Thermodynamic Quantities for Selected Substances at 298.15 K (25°C)
The value of ΔS° for the catalytic hydrogenation of ethene to ethane, is J/K.

A) +101.9
B) +112.0
C) - 101.9
D) - 120.5
E) - 232.5

Question 79

Use the table below to answer the questions that follow.
Thermodynamic Quantities for Selected Substances at 298.15 K (25°C)
The value of ΔS° for the oxidation of carbon to carbon
Is J/K. The combustion of carbon, as in charcoal briquettes, in the presence of abundant oxygen produces carbon dioxide.

A) +2.9
B) - 2.9
C) - 205.0
D) +205.0
E) +424.3

Question 80

Use the table below to answer the questions that follow.
Thermodynamic Quantities for Selected Substances at 298.15 K (25°C)
The value of ΔG° at 25 °C for the decomposition of POCl₃ into its constituent elements, is kJ/mol.

A) +606.2
B) - 1,109
C) +1,109
D) - 606.2
E) - 1,005