Deck 18: Entropy, Free Energy, and Equilibrium

Question 1

How many types of rotations does a diatomic molecule exhibit?

A) 0
B) 1
C) 2
D) 3
E) 4

Answer 1

2

Question 2

What is defined as a measure of the randomness or disorder of a system?

A) Gibbs free energy
B) Entropy
C) Spontaneous process
D) Nonspontaneous process
E) Enthalpy

Answer 2

Entropy

Question 3

The most probable state is the one with the ________.

A) highest energy
B) largest number of possible arrangements
C) lowest number of possible arrangements
D) most symmetry
E) highest enthalpy

Answer 3

largest number of possible arrangements

Question 4

A spontaneous endothermic reaction always

A) causes the surroundings to get colder.
B) bursts into flame.
C) requires a spark to initiate it.
D) releases heat to the surroundings.

Question 5

How many types of vibrations does a bent triatomic molecule exhibit?

A) 0
B) 1
C) 2
D) 3
E) 4

Question 6

How many types of rotations does a bent triatomic molecule exhibit?

A) 0
B) 1
C) 2
D) 3
E) 4

Question 7

What is defined as a process that may occur under a specific set of conditions?

A) Conditional process
B) Nonspontaneous process
C) Specified process
D) Spontaneous process
E) Conditionality law

Question 8

Which statement is correct?

A) The standard entropy of a gas phase substance is less than the standard entropy of the same substance in the solid phase.
B) For two different substances in the same phase, the substance with the more complex structure has the lower entropy.
C) The more highly ordered allotrope of an element has a higher entropy.
D) The entropies of elements and compounds are always positive.
E) For a monatomic gas, the gas with the lower molar mass has the greater entropy.

Question 9

Which, if any, of the following processes is spontaneous under the specified conditions?

A) H₂O(l) → H₂O(s) at 25°C, 1 atm pressure
B) CO₂(s) → CO₂(g) at 0°C, 1 atm pressure
C) 2H₂O(g) → 2H₂(g) + O₂(g) at 25°C, 1 atm pressure
D) C(graphite) → C(diamond) at 25°C, 1 atm pressure
E) None of these processes is spontaneous.

Question 10

What is defined as the measure of accessible energy levels of a substance at 1 atm?

A) Atmospheric disorder
B) Atmospheric pressure
C) Atmospheric entropy
D) Specific pressure
E) Standard entropy

Question 11

Which of the following is an example of a nonspontaneous process?

A) Ice melting at room temperature
B) Sodium metal reacting violently with water
C) Rusting of iron at room temperature
D) A ball rolling downhill
E) Water freezing at room temperature

Question 12

According to which scientific law does the entropy of the universe increase in spontaneous processes and remain unchanged in equilibrium processes?

A) 1^st law of thermodynamics
B) 1^st law of entropy
C) 1^st universal law
D) 2^nd law of thermodynamics
E) 3^rd law of thermodynamics

Question 13

Which is a statement of the second law of thermodynamics?

A) The energy of the universe is constant.
B) The entropy of the universe is constant.
C) The enthalpy of the universe is constant.
D) The energy of the universe is decreasing.
E) The entropy of the universe is increasing.

Question 14

If a certain process has ΔS_univ > 0 at 25°C, the process may be described as

A) exothermic.
B) endothermic.
C) spontaneous.
D) moving rapidly toward equilibrium.
E) violating the second law of thermodynamics.

Question 15

When a sky diver free-falls through the air, the process is

A) nonspontaneous because he is accelerating due to the force applied by gravity.
B) nonspontaneous because he is losing potential energy.
C) nonspontaneous because he had planned the jump for two weeks.
D) spontaneous.
E) in equilibrium.

Question 16

Which has the largest entropy?

A) C (diamond)
B) C (graphite)
C) H₂O(l)
D) F₂(l)
E) O₂(g)

Question 17

Which of these species has the highest entropy (S°) at 25°C?

A) CH₃OH(l)
B) CO(g)
C) MgCO₃(s)
D) H₂O(l)
E) Si(s)

Question 18

Which statement is correct?

A) Heating always decreases the entropy of a system.
B) The reaction that results in an increase in the number of moles of gas always decreases the entropy of a system.
C) The greater number of particles leads to a smaller number of microstates.
D) An increase in the temperature decreases all types of molecular motions.
E) The solvation process usually leads to an increase in entropy.

Question 19

How many types of vibrations does a diatomic molecule exhibit?

A) 0
B) 1
C) 2
D) 3
E) 4

Question 20

Which response includes all of the following processes that are accompanied by an increase in entropy? 1. I₂(s) → I₂(g)
2) 2I(g) → I₂(g)
3) 2NH₃(g) → N₂(g) + 3H₂(g)
4) Mg²⁺(aq) + 2OH^-(aq) → Mg(OH)₂(s)

A) 1, 2
B) 1, 3
C) 3, 4
D) 3
E) 2, 4

Question 21

Which of the following results in a decrease in the entropy of the system?

A) O₂(g), 300 K → O₂(g), 400 K
B) H₂O(s), 0°C → H₂O(l), 0°C
C) N₂(g), 25°C → N₂(aq), 25°C
D) NH₃(l), -34.5°C → NH₃(g), -34.5°C
E) 2H₂O₂(g) → 2H₂O(g) + O₂(g)

Question 22

Which is necessary for a process to be spontaneous?

A) ΔH_sys < 0
B) ΔS_sys > 0
C) ΔS_surr < 0
D) ΔS_univ > 0
E) ΔG_sys = 0

Question 23

What is ΔS° for the reaction SO₂(s) + NO₂(g) → SO₃(g) + NO(g)?

A) 53.6 J/K • mol
B) -53.6 J/K • mol
C) -22.2 J/K • mol
D) 474.8 J/K • mol
E) -474.8 J/K • mol

Question 24

What is ΔS° at 298 K for the following reaction? Fe₂O₃(s) + 3CO(g) → 3CO₂(g) + 2Fe(s)

A) 12.7 J/K • mol
B) -12.7 J/K • mol
C) 527.9 J/K • mol
D) 157.2 J/K • mol
E) 4.6 J/K • mol

Question 25

What is ΔS° for the combustion of propane? C₃H₈(g) + 5O₂(g) → 3CO₂(g) + 4H₂O(g)

A) -100.7 J/K
B) -72.6 J/K
C) 72.6 J/K
D) 100.7 J/K
E) 877.2 J/K

Question 26

What term is given to the fact that the entropy of a perfect crystalline solid is zero at absolute zero?

A) 1^st law of thermodynamics
B) 2^nd law of thermodynamics
C) 3^rd law of thermodynamics
D) crystalline lattice theory
E) absolute crystallinity

Question 27

What is ΔS° for the following reaction? SiCl₄(g) + 2Mg(s) → 2MgCl₂(s) + Si(s)

A) -254.96 J/K • mol
B) -198.02 J/K • mol
C) +198.02 J/K • mol
D) +254.96 J/K • mol
E) +471.86 J/K • mol

Question 28

What is ΔS° for the reaction SO₃(g) + H₂O(l) → H₂SO₄(aq)?

A) 169.2 J/K • mol
B) 343.2 J/K • mol
C) -169.2 J/K • mol
D) -29.4 J/K • mol
E) 29.4 J/K • mol

Question 29

Which is the thermodynamic condition for a spontaneous process at constant T and P?

A) ΔS > 0
B) ΔS < 0
C) ΔG < 0
D) ΔG > 0
E) ΔG° = 0

Question 30

Which is true for a system at equilibrium?

A) ΔS°_sys = ΔS°_surr
B) ΔS°_sys = -ΔS°_surr
C) ΔS°_sys = ΔS°_surr = 0
D) ΔS°_univ > 0
E) ΔS°_univ < 0

Question 31

Which is a statement of the third law of thermodynamics?

A) The entropy of the universe is increasing.
B) The entropy of the universe is constant.
C) For a perfect crystalline solid, the entropy at T = 0 K is zero.
D) The energy of the universe is constant.
E) The entropy of all elements are zero.

Question 32

What is ΔS° for the following reaction? 4Cr(s) + 3O₂(g) → 2Cr₂O₃(s)

A) -549.19 J/K • mol
B) -148.26 J/K • mol
C) +148.26 J/K • mol
D) +66.22 J/K • mol
E) +871.80 J/K • mol

Question 33

Which reaction has the largest ΔS°?

A) 2N₂H₄(g) → 2NH₃(g) + H₂(g) + N₂(g)
B) O₂(g) + 2H₂(g) → 2H₂O(l)
C) O₂(g) + 2H₂(g) → 2H₂O(g)
D) N₂(g) + 3H₂(g) → 2NH₃(g)
E) 2NO(g) → N₂O₂(g)

Question 34

What is ΔS° for the following reaction? 2Cl₂(g) + SO₂(g) → SOCl₂(g) + Cl₂O(g)

A) -118.2 J/K • mol
B) -104.8 J/K • mol
C) 104.8 J/K • mol
D) 118.2 J/K • mol
E) 1270.0 J/K • mol

Question 35

Elemental boron can be formed by the reaction of boron trichloride with hydrogen. 2BCl₃(g) + 3H₂(g) → 2B(s) + 6HCl(g)

A) -18.2 J/K • mol
B) 18.2 J/K • mol
C) 289.5 J/K • mol
D) 370.4 J/K • mol
E) 579.0 J/K • mol

Question 36

What is ΔS° at 25°C for the reduction of lead(II) oxide by charcoal? 2PbO(s) + C(s) → 2Pb(s) + CO₂(g)

A) +198.7 J/K • mol
B) +488.0 J/K • mol
C) +353.7J/K • mol
D) -203.3 J/K • mol
E) +203.3 J/K • mol

Question 37

What is the change in entropy for the vaporization of 18 g of H₂O at 100°C? At this temperature, the molar enthalpy of vaporization for water is 44.0 kJ/mol.

A) 44 kJ/mol
B) 440 J/K
C) 117.9 J/K
D) -41 kJ/K
E) -440 kJ/K

Question 38

Which is always true for an exothermic process?

A) q_sys > 0, ΔS_surr < 0
B) q_sys < 0, ΔS_surr > 0
C) q_sys < 0, ΔS_surr < 0
D) q_sys > 0, ΔS_surr > 0
E) w < 0

Question 39

A negative sign for ΔG indicates that, at constant T and P,

A) the reaction is exothermic.
B) the reaction is endothermic.
C) the reaction is fast.
D) the reaction is spontaneous.
E) ΔS of the system must be greater than zero.

Question 40

At constant temperature and pressure, which is the correct relationship between ΔG and other thermodynamic quantities?

A) ΔG = ΔH - TΔS
B) ΔG = ΔH + TΔS
C) ΔG = ΔU - TΔS
D) ΔG = -TΔS
E) ΔG = q/T

Question 41

Which of the following will decrease the entropy of an inert gas system?

A) Increasing the temperature
B) Decreasing the volume
C) Adding a different inert gas to the system
D) Increasing the molar mass
E) Decreasing the pressure

Question 42

For a chemical reaction to be spontaneous only at high temperatures, which conditions must be met?

A) ΔS° > 0, ΔH° > 0
B) ΔS° > 0, ΔH° < 0
C) ΔS° < 0, ΔH° < 0
D) ΔS° < 0, ΔH° > 0
E) ΔG° > 0

Question 43

The temperature at which the following process reaches equilibrium at 1.0 atm is the normal boiling point of hydrogen peroxide. (R = 8.314 J/K • mol) H₂O₂(l) H₂O₂(g)
Use the following thermodynamic information at 298 K to estimate this temperature.

A) 120°C
B) 144°C
C) 196°C
D) 418°C
E) 585°C

Question 44

Ozone (O₃) in the atmosphere can react with nitric oxide (NO) as follows. O₃(g) + NO(g) → NO₂(g) + O₂(g). ΔH°_rxn = -199 kJ/mol, ΔS°_rxn = -4.1 J/K • mol
What is ΔG°_rxn for this reaction at 25°C?

A) 1020 kJ/mol
B) -1.22 × 10³ kJ/mol
C) 2.00 × 10³ kJ/mol
D) -1.42 × 10³ kJ/mol
E) -198 kJ/mol

Question 45

What is ΔG°_rxn for the following reaction? 3NO₂(g) + H₂O(l) → 2HNO₃(l) + NO(g)

A) +8.7 kJ/mol
B) +192.2 kJ/mol
C) -178.6 kJ/mol
D) -192.2 kJ/mol
E) +639.1 kJ/mol

Question 46

Calculate ΔG°_rxn for the following reaction of ammonia with fluorine. 2NH₃(g) + 5F₂(g) → N₂F₄(g) + 6HF(g)

A) 179.1 kJ/mol
B) -179.1 kJ/mol
C) 1539.7 kJ/mol
D) -1539.7 kJ/mol
E) -211.9 kJ/mol

Question 47

What is ΔG°_rxn for the following reaction? SiCl₄(g) + 2Mg(s) → 2MgCl₂(s) + Si(s)

A) 566.60 kJ/mol
B) 50.38 kJ/mol
C) 25.19 kJ/mol
D) -25.19 kJ/mol
E) -566.60 kJ/mol

Question 48

What is ΔG°_rxn for the following reaction? 2NO(g) + Cl₂(g) → 2NOCl(g)

A) -40.40 kJ/mol
B) +40.40 kJ/mol
C) -20.20 kJ/mol
D) +20.20 kJ/mol
E) +152.90 kJ/mol

Question 49

Which of the following has ΔG°_f = 0 at 25^oC?

A) H₂O(l)
B) H₂O(g)
C) Na(s)
D) O₃(g)
E) O(g)

Question 50

Nitric oxide reacts with chlorine to form NOCl. 2NO(g) + Cl₂(g) → 2NOCl(g) What is ΔG°_rxn for this reaction at 550. K?

A) -143.76 kJ/mol
B) -78.78 kJ/mol
C) -22.24 kJ/mol
D) -10.6 kJ/mol
E) 66600 kJ/mol

Question 51

Sodium carbonate can be made by heating sodium bicarbonate: 2NaHCO₃(s) → Na₂CO₃(s) + CO₂(g) + H₂O(g)
At 25°C, for this reaction, ΔH°_rxn = 128.9 kJ/mol and ΔG°_rxn = 33.1 kJ/mol. Above what minimum temperature will the reaction become spontaneous under standard state conditions?

A) 0.4 K
B) 3.9 K
C) 321 K
D) 401 K
E) 525 K

Question 52

What is ΔG°_rxn at 298 K for the following reaction? 2Cl₂(g) + SO₂(g) → SOCl₂(g) + Cl₂O(g)

A) 129.3 kJ/mol
B) 133.4 kJ/mol
C) 196.0 kJ/mol
D) 199.8 kJ/mol
E) 229.6 kJ/mol

Question 53

What is ΔG°_rxn for the combustion of propane? C₃H₈(g) + 5O₂(g) → 3CO₂(g) + 4H₂O(g)

A) -2073.1 kJ/mol
B) -1387.3 kJ/mol
C) -598.5 kJ/mol
D) +598.5 kJ/mol
E) +2073.1 kJ/mol

Question 54

The element oxygen was prepared by Joseph Priestley in 1774 by heating mercury(II) oxide: HgO(s) → Hg(l) + ½O₂(g), ΔH° = 90.84 kJ/mol. Estimate the temperature at which this reaction will become spontaneous under standard state conditions.

A) 108 K
B) 430. K
C) 620. K
D) 775 K
E) 840. K

Question 55

The temperature at which the following process reaches equilibrium at 1.0 atm is the normal melting point for phosphoric acid. H₃PO₄(s) H₃PO₄(l)
Use the following thermodynamic data at 298 K to estimate this temperature.

A) 286 K
B) 305 K
C) 315 K
D) 347 K
E) 3170 K

Question 56

Elemental boron can be formed by the reaction of boron trichloride with hydrogen. 2BCl₃(g) + 3H₂(g) → 2B(s) + 6HCl(g)
What is ΔG°_rxn for this reaction?

A) -293.4 kJ/mol
B) 293.4 kJ/mol
C) -205.6 kJ/mol
D) 205.6 kJ/mol
E) -2141.6 kJ/mol

Question 57

Sulfuryl dichloride may be formed from the reaction of sulfur dioxide and chlorine. SO₂(g) + Cl₂(g) → SO₂Cl₂(g) What is ΔG°_rxn for this reaction at 600 K?

A) -162.8 kJ/mol
B) -40.1 kJ/mol
C) -28.4 kJ/mol
D) 28.4 kJ/mol
E) 162.8 kJ/mol

Question 58

For a chemical reaction to be spontaneous at all temperatures, which conditions must be met?

A) ΔS°_rxn > 0, ΔH°_rxn > 0
B) ΔS°_rxn > 0, ΔH°_rxn < 0
C) ΔS°_rxn< 0, ΔH°_rxn < 0
D) ΔS°_rxn < 0, ΔH°_rxn > 0
E) ΔS°_rxn = 0, ΔH°_rxn = 0

Question 59

HI has a normal boiling point of -35.4°C, and its ΔH_vap is 21.16 kJ/mol. What is the molar entropy of vaporization (ΔS_vap) of HI?

A) 598 J/K • mol
B) 68.6 J/K • mol
C) 75.2 J/K • mol
D) 0.068 J/K • mol
E) 89.0 J/K • mol

Question 60

Hydrogen sulfide decomposes according to the following reaction: 2H₂S(g) → 2H₂(g) + S₂(g)
For this reaction at 298 K, ΔS°_rxn = 78.1 J/K • mol, ΔH°_rxn = 169.4 kJ/mol, and ΔG°_rxn = 146.1 kJ/mol. What is ΔG°_rxn at 900. K?

A) -69881 kJ/mol
B) 48.4 kJ/mol
C) 99.1 kJ/mol
D) 240 kJ/mol
E) 441 kJ/mol

Question 61

Consider the figure below which shows ΔG° for a chemical process plotted against absolute temperature. From this plot, it is reasonable to conclude that:

A) ΔH° > 0, ΔS° > 0
B) ΔH° > 0, ΔS° < 0
C) ΔH° < 0, ΔS° > 0
D) ΔH° < 0, ΔS° < 0
E) None of these choices is correct.

Question 62

The absolute standard entropy of atom X(g) is 100 J/K • mol. Which is a reasonable value for the absolute standard entropy of X₂(g)?

A) 200 J/K • mol
B) 170 J/K • mol
C) 100 J/K • mol
D) 80 J/K • mol
E) 50 J/K • mol

Question 63

For the following process, which is true?

A) ΔH > 0, ΔS > 0
B) ΔH > 0, ΔS < 0
C) ΔH < 0, ΔS > 0
D) ΔH < 0, ΔS < 0
E) ΔH > 0, ΔS = 0

Question 64

For the process C₆H₆(l) <-----> C₆H₆(s) at a temperature above the freezing point of C₆H₆,

A) ΔS is positive.
B) ΔH is positive.
C) ΔG is positive.
D) ΔG = O.

Question 65

In 1774 Joseph Priestly prepared oxygen by heating mercury(II) oxide according to the reaction HgO(l) <----> Hg(l) + ½O₂(g), for which ΔH^o = 90.84 kJ/mol and ΔS^o = 108 J/K.mol. Which of the following statements is true for this reaction?

A) The reaction is spontaneous only at low temperatures.
B) The reaction is spontaneous at all temperatures.
C) ΔG^o becomes less favorable as temperature increases.
D) The reaction is spontaneous only at high temperatures.
E) The reaction is at equilibrium at 25^oC and 1 atm pressure.

Question 66

Which statement is correct?

A) Oxygen is formed during the metabolism of food.
B) The metabolism process results in a positive ΔG^o.
C) ADP is hydrolyzed to ATP and phosphoric acid in the body.
D) A protein is a polymer made of carbohydrate units.
E) ATP functions to store energy until it is needed by the body.

Question 67

Calculate ΔG° for the combustion of ethanol vapor, C₂H₅OH(g), at 750.°C in oxygen to form carbon dioxide and water vapor. The following data are valid at 25°C:

A) -1407 kJ/mol
B) -2151 kJ/mol
C) -1307 kJ/mol
D) -4486 kJ/mol
E) -1377 kJ/mol

Question 68

Is the following process spontaneous?

A) Yes, because ΔH > 0.
B) No, because ΔH < 0.
C) Yes, because ΔS > 0.
D) No, because ΔS < 0.
E) It's impossible to tell without knowing the temperature of the system.

Question 69

Below are energy level diagrams for two different atoms. Based on the diagrams, which atom has the larger standard molar entropy at T = 298 K?

A) Atom 1 has the larger standard molar entropy because the energy of its ground state is larger than the energy of the ground state of atom 2.
B) Atom 2 has the larger standard molar entropy because the energy of its ground state is smaller than the energy of the ground state of atom 1.
C) Atom 1 has the larger standard molar entropy because it has fewer energy levels at lower energy values than atom 2.
D) Atom 2 has the larger standard molar entropy because it has more energy levels at lower energy values than atom 1.
E) Both atoms have the same value of the standard molar entropy at T = 298 K.

Question 70

Which species will have the greatest absolute entropy at 25°C?

A) Ne(g)
B) C₂H₂(g)
C) H₂O(l)
D) C₂H₅OH(l)
E) C₄H₁₀(g)

Question 71

The higher the pressure of a gas sample, the greater is its entropy.

Question 72

Which statement is correct?

A) Reaction of ADP and alanine results in ATP in the body.
B) A positive ΔG° value means that the reaction is not product favored.
C) CO₂ is released when ADP reacts with an amino acid.
D) Phosphoric acid is one of the products of the reaction of ADP with alanine.
E) Hydrolysis of ATP requires NaOH.

Question 73

Which species will have the lowest absolute entropy at 25°C?

A) C₂H₅OH(l)
B) C₂H₂(g)
C) C₃H₈(g)
D) C₃H₇OH(l)
E) C₂H₆(g)

Question 74

The reaction of methane with water to form carbon dioxide and hydrogen is nonspontaneous at 98 K. At what temperature will this system make the transition from nonspontaneous to spontaneous? The following data are valid at 298 K: CH₄(g) + 2H₂O(g) CO₂(g) + 4H₂(g)

A) 658 K
B) 683 K
C) 955 K
D) 1047 K
E) 1229 K

Question 75

As the molar mass of a compound increases, the entropy ________.

A) decreases
B) is constant
C) increases

Question 76

Consider the figure below which shows ΔG° for a chemical process plotted against absolute temperature. From this plot, it is reasonable to conclude that:

A) ΔH° > 0, ΔS° > 0
B) ΔH° > 0, ΔS° < 0
C) ΔH° < 0, ΔS° > 0
D) ΔH° < 0, ΔS° < 0
E) None of these choices is correct.

Question 77

Which of the following substances has the greatest entropy per mole?

A) O₂(g)
B) N₂(g)
C) CO(g)
D) CO₂(g)
E) C₄H₁₀(g)

Question 78

At temperatures below 273 K, it is observed that liquid water spontaneously freezes to form solid ice. What must be true about the entropy changes of the system and surroundings for this process?

A) ΔS_sys > 0, ΔS_surr > 0
B) ΔS_sys < 0, ΔS_surr > 0
C) ΔS_sys < 0, ΔS_surr < 0
D) ΔS_sys > 0, ΔS_surr < 0
E) ΔS_sys = 0, ΔS_surr > 0

Question 79

The heat of vaporization of 1-pentanol is 55.5 kJ/mol, and its entropy of vaporization is 148 J/K•mol. What is the approximate boiling point of 1-pentanol?

A) 100^oC
B) 375 ^oC
C) 0 ^oC
D) 25 ^oC

Question 80

Consider the figure below which shows ΔG° for a chemical process plotted against absolute temperature. Which one of the following is an incorrect conclusion, based on the information in the diagram?

A) ΔH° > 0.
B) ΔS° > 0.
C) The reaction is spontaneous at high temperatures.
D) ΔS° increases with temperature while ΔH° remains constant.
E) There exists a certain temperature at which ΔH° = TΔS°.