Deck 13: Spontaneous Change: Entropy and Gibbs Energy

Question 1

Entropy is related to the way in which the energy of a system is distributed among the available microscopic energy levels.

Answer 1

True

Question 2

The entropy of a pure perfect crystal at 25 K is zero.

Answer 2

False

Question 3

A zero ΔG means the system is at equilibrium.

Answer 3

True

Question 4

The chemical potential of a substance,m,represents the ability of a substance to change the Gibbs energy of a system.

Question 5

An increase or a decrease in the number of microstates parallels an increase or
decrease in the number of microscopic particles and the space available to them.

Question 6

A non spontaneous reaction can be made to occur by coupling it with a spontaneous reaction to form an overall spontaneous reaction.

Question 7

A spontaneous process will occur only if an external action is continually applied.

Question 8

A spontaneous process:

A)will happen quickly
B)releases large amounts of energy
C)requires an external action in order to begin reacting
D)will continue on its own once begun
E)is never endothermic

Question 9

In a reversible reaction,a forward spontaneous reaction corresponds to a negative ΔG.

Question 10

?_rG ? is independent of temperature.

Question 11

Entropy changes depend on the quantities of substances involved.

Question 12

As the activity a of a substances increases so does its chemical potential m.

Question 13

Non spontaneous reactions and spontaneous reactions cannot be coupled.

Question 14

ΔG is positive for a spontaneous reaction.

Question 15

Standard Gibbs energy of formation requires the reactants be compounds in their standard state.

Question 16

If a process is spontaneous,the reverse process is non spontaneous.

Question 17

The entropy of a system always increases for a spontaneous process.

Question 18

A microstate is a specific microscopic configuration describing how particles
of a system are distributed among the available energy levels.

Question 19

Standard molar entropy,S^∘,increases as molecular complexity increases.

Question 20

An increase in entropy is observed when a liquid forms from a gas.

Question 21

The change in Gibbs energy for a reaction:

A)= ΔH - TΔS
B)= q (heat)
C)= ΔS + TΔH
D)= ΔS - TΔH
E)= ΔH + TΔS

Question 22

Which material has the largest entropy?

A)pure water
B)powdered sugar
C)salt water
D)crystalline salt
E)cannot be determined

Question 23

Which of the following has the highest entropy?

A)1 mole of liquid water at 30 °C
B)1 mole of water vapor at 30 °C
C)1 mole of regular ice at -10 °C
D)1 mole of "dry ice" at -10 °C
E)1 mole of water under 10 atm of pressure at -10 °C

Question 24

In a sealed container,the rate of dissolving is equal to the rate of crystallization.Therefore we would expect:

A)ΔG < 0
B)ΔG > 0
C)ΔG = 0
D)ΔS = 0
E)must know ΔH to determine

Question 25

The change in Gibbs energy of a reaction:

A)= work
B)predicts speed
C)= ΔH + TΔS
D)depends on the standard state chosen
E)tells us if the reaction is spontaneous or not

Question 26

Find correct statements.
I.A spontaneous process is a process that occurs in a system left to itself.
II.A non spontaneous process will not occur unless some external force is applied.
III.If a reaction is spontaneous,the reverse is also spontaneous.
IV.Only spontaneous processes occur naturally.
V.Entropy is inversely proportional to the degree of randomness.

A)I ,II and V
B)II ,III ,and IV
C)I ,II ,and IV
D)I ,III and IV
E)I ,IV ,and V

Question 27

The normal melting and boiling points of SO₂ are 198 and 263 K,respectively.For a plot of the standard molar entropy of SO₂ versus temperature,which of the following is INCORRECT?

A)At 263 K,S° is constant.
B)S° increases with increasing temperature.
C)S° equals zero at 0 K.
D)At 198 K,S° increases by the value of △_fusS.
E)At 263 K,S° jumps suddenly as SO₂ undergoes phase change.

Question 28

The maximum quantity of energy available for useful work is:

A)constant
B)Gibbs energy change
C)the entropy change
D)the internal energy change
E)the enthalpy change

Question 29

Indicate the statement(s)which is (are)true for the process:
Al⁺³(aq)+ 3 OH^-(aq)→ Al(OH)₃(s)
If it occurs in a closed container.
I.ΔS increases because the final molecule is more complicated.
II.Entropy decreases because the product is in the solid phase.
III.The two ions achieve a high degree of order as they crystalize,therefore ΔS is positive.
IV.Entropy of the system is unchanged because the system is sealed and at a constant temperature.

A)I and II
B)I and III
C)II only
D)I,II,IV
E)I and IV

Question 30

The Gibbs energy change for a reaction is -298 kJ.The reaction is therefore:

A)exothermic
B)irreversible
C)spontaneous
D)endothermic
E)nonspontaneous

Question 31

Which of the following substances under equal conditions and in the same phase has the greatest molar entropy?

A)NO
B)NO₂
C)N₂O₃
D)N₂O₄
E)N₂O₅

Question 32

If ΔG < 0 for a reaction,then the reaction is said to be:

A)endothermic
B)reversible
C)spontaneous
D)exothermic
E)fast

Question 33

Which of the following has the largest molar entropy?

A)I₂(g)
B)Xe(g)
C)H₂(g)
D)He(g)
E)O₂(g)

Question 34

Choose the INCORRECT statement.

A)The third law of thermodynamics states that the entropy of a pure crystal at 298 K is zero.
B)?_rS° = ? (? S°) products - ? (? S°) reactants .
C)The activity of pure liquids or pure solids is 1.
D)?_rG ° = -RT ln K_eq.
E)?_rG ° = ?_rH° - T?_rS°.

Question 35

Which of the following best expresses the increase in entropy associated with melting and sublimation,respectively?

A)Δ_fusS - Δ_subS = 0
B)Δ_fusS = 144.3 J/mol-K,Δ_subS = 9.0 J/mol-K
C)Δ_fusS = 9.0 J/mol-K,Δ_subS = -144.3 J/mol-K
D)ΔH for both processes is zero
E)Δ_fusS = 9.0 J/mol-K,Δ_subS= 144.3 J/mol-K

Question 36

Which of the following statements are true?
I.Liquids have more entropy than their solids.
II.Solutions have more entropy than the solids dissolved.
III.Gases and their liquids have equal entropy.
IV.Gases have less entropy than their solids.
V.Entropy of a substance increases as its temperature increases.

A)II ,III ,and V
B)I ,III ,and V
C)I ,IV ,and V
D)I ,II ,and V
E)II ,IV and V

Question 37

Which of the following relations is true for the molar entropy of sublimation of a substance?

A)Δ_subS = Δ_fusS + Δ_vapS
B)Δ_subS < Δ_vapS
C)Δ_subS = Δ_fusS - Δ_vapS
D)Δ_subS < (Δ_fusS + Δ_vapS₎
E)Δ_subS > (Δ_fusS + Δ_vapS₎

Question 38

Choose the INCORRECT statement.

A)One form of the second law of thermodynamics is all spontaneous processes produce an increase in the entropy of the universe.
B)Gibbs energy is defined by: G = H - TS.
C)If ΔG < 0,the process is spontaneous.
D)If ΔG > 0,the process is nonspontaneous.
E)If ΔG = 0,the process is spontaneous.

Question 39

Which of the following processes would result in a decrease in system entropy?

A)melting of an ice cube
B)sublimation of a moth ball
C)evaporation of a puddle of gasoline
D)a glass of cool lemonade warming in the sun
E)condensation of water vapor on a cold windshield

Question 40

Choose the correct statements concerning entropy.
I.Following the mixing of two gases,ΔS is positive.
II.Entropy is a thermodynamic property related to the degree of disorder.
III.If the temperature of a gas is decreased,ΔS is positive.
IV.Molecules in the liquid state have higher entropy than the same molecules in the gaseous state.

A)I and III
B)I,II,III
C)I and II
D)I,II,IV
E)II and III

Question 41

For the reaction PCl₅(g)→ PCl₃(g)+ Cl₂(g)at 298 K,K_eq = 1.87 × 10^-7,what is Δ_rG ° and is the reaction spontaneous?

A)3.84 × 10⁴ kJ/mol,no
B)7.68 kJ/mol,no
C)-7.68 kJ/mol,yes
D)38.4 kJ/mol,no
E)-38.4 kJ/mol,yes

Question 42

A reaction is spontaneous if:
I.ΔG is a negative value
II.both enthalpy and entropy increase
III.ΔH is negative and ΔS is positive
IV.both enthalpy and entropy decrease
V.ΔH is positive and ΔS is negative

A)I and III
B)I and II
C)II and V
D)III and IV
E)II and IV

Question 43

The equilibrium constant for the reaction below is 7.2 × 10^-4 at 298 K and 1 atm.
HNO₂(aq)+ H₂O(l)⇌ NO₂^-(aq)+ H₃O⁺(aq)
When [HNO₂(aq)] = 1.0 M and [NO₂^-(aq)] = [H₃O⁺(aq)] = 1.0 × 10^-5 M,calculate ΔG.

A)-39.1 kJ/mol
B)+17.9 kJ/mol
C)-17.9 kJ/mol
D)+39.1 kJ/mol
E)-23.02 kJ/mol

Question 44

The following reaction is exothermic.
2 N₂O(g)→ 2 N₂(g)+ O₂(g)
This means the reaction:

A)will be spontaneous at all temperatures
B)will be spontaneous only at high temperature
C)will be spontaneous only at low temperatures
D)is not spontaneous at any temperature
E)cannot determine without temperature

Question 45

Consider the reaction of 25.0 mL of 0.20 M AgNO₃(aq)with 25.0 mL of 0.20 M NaBr(aq)to form AgBr(s)at 25 °C.What is ΔG for this reaction? The K_sp of AgBr is 5.0 × 10^-13 at 25 °C.

A)-58.8 kJ/mol
B)-70.2 kJ/mol
C)+58.8 kJ/mol
D)+70.2 kJ/mol
E)-28.3 kJ/mol

Question 46

The equilibrium constant for the reaction below is 7.2 × 10^-4 at 298 K and 1 atm.
HNO₂(aq)+ H₂O(l)⇌ NO₂^-(aq)+ H₃O⁺(aq)
Which of the below statements is TRUE under the following conditions:
[HNO₂(aq)] = 1.0 M and [NO₂^-(aq)] = [H₃O⁺(aq)] = 1.0 × 10^-5 M

A)the reaction is at equilibrium
B)the forward reaction is spontaneous
C)the reverse reaction is spontaneous
D)the forward reaction is endothermic
E)the reverse reaction is exothermic

Question 47

The following reaction is endothermic.
2 NH₃(g)→ N₂(g)+ 3 H₂(g)
This means the reaction:

A)will be spontaneous at high temperature
B)will be spontaneous at low temperature
C)is not spontaneous at any temperature
D)is spontaneous at all temperatures
E)cannot determine without temperature

Question 48

Which of the following combinations of signs for △H and △S will always result in a reaction being non spontaneous?

A)ΔH+,ΔS-
B)ΔH-,ΔS+
C)ΔH-,ΔS-
D)ΔH+,ΔS+
E)cannot determine without temperature

Question 49

For Cl₂O(g)+ 3/2 O₂(g)→ 2 ClO₂ △_rH° = 126 kJ/mol,and Δ_rS° = -74.9 J/(mol K)at 377 °C.What is K_eq?

A)0.97
B)6.12 × 10^-7
C)4.27 × 10^-22
D)9.17 × 10^-15
E)1.07 × 10¹⁴

Question 50

For an exothermic reaction to be non spontaneous at high temperatures,the enthalpy must be ________ while the entropy is ________.

A)positive,also positive
B)positive,negative
C)a relatively small negative value,also negative
D)a relatively large negative value,positive
E)a very large negative value,also negative

Question 51

Choose the INCORRECT statement about coupled reactions.

A)The usual practice of coupling reactions is to join two nonspontaneous reactions.
B)The usual reason to couple reactions is to produce an overall spontaneous reaction.
C)The reaction added to a nonspontaneous reaction needs to be spontaneous.
D)The reaction added to a nonspontaneous reaction needs to be more spontaneous than the original reaction is nonspontaneous.
E)One of the coupled reactions has a negative ΔG,the other a positive ΔG.

Question 52

Consider the reaction:
N₂(g)+ 3 X₂(g)→ 2 NX₃(g)
△_fH° (kJ/mol)0.0 0.0 43
S° (J/(mol K))192 210 172
What is K_eq for this reaction at 591 K?

A)2.3 × 10¹⁷
B)4.3 × 10^-18
C)1.04
D)0.96
E)132

Question 53

Which of the following quantities for an element has a value of zero in the standard state?
I.D_fH°
II.D_fG°
III.S°

A)I only
B)II only
C)III only
D)I and II
E)I,II,and III

Question 54

If ΔG is positive for a certain reaction,then:

A)the reaction is spontaneous
B)the reverse of the reaction is spontaneous
C)the system is in equilibrium
D)one would need to know the Kelvin temperature to determine spontaneity
E)there would be no reaction possible for a negative value

Question 55

For the reaction: CO(g)+ 2 H₂(g)→ CH₃OH(g)
K_p = 91.4 at 350 K and K_p = 2.05 × 10^-4 at 298 K.
What is the value of Δ_rH°?

A)49.9 kJ/mol
B)2.08 × 10³ kJ/mol
C)3.74 × 10^-2 kJ/mol
D)217 kJ/mol
E)446 kJ/mol

Question 56

For the reaction PCl₅ (g)⇌ PCl₃ (g)+ Cl₂ (g),K_c = 0.0454 at 261 °C.If a vessel is filled with theses gases such that the initial concentrations are [PCl₅] = 0.2 M,[PCl₃] = 0.2 M,and [Cl₂] = 2.25 M,the value of the reaction quotient is:

A)Q_c = 1.8
B)Q_c = 0.56
C)Q_c = 2.8
D)Q_c = 0.0454
E)Q_c = 1

Question 57

If the vapor pressure of water in an open system at 25 °C is 23.8 mmHg,what is Δ_rG for the reaction below at 25 °C?
H₂O(l)→ H₂O(g,23.8 mmHg)

A)0 kJ/mol
B)-8.58 kJ/mol
C)+8.58 kJ/mol
D)-0.720 kJ/mol
E)+0.720 kJ/mol

Question 58

Which of the following quantities is practically independent of temperature?
I.ΔH
II.ΔS
III.ΔG

A)I only
B)II only
C)III only
D)I and II
E)I,II,and III

Question 59

Choose the INCORRECT statement.

A)The van't Hoff equation is ln
B)K_eq is independent of temperature.
C)In a thermodynamic equilibrium constant expression,the activity of a gas is replaced by its partial pressure in atmosphere.
D)In a K_eq expression,the activity of an aqueous species can be approximated by the numerical value of its molarity.
E)If ΔG = 0,the process is at equilibrium.

Question 60

For the reaction PCl₅ (g)⇌ PCl₃ (g)+ Cl₂ (g),K_c = 0.0454 at 261 °C.If a vessel is filled with theses gases such that the initial concentrations are [PCl₅] = 0.2 M,[PCl₃] = 0.2 M,and [Cl₂] = 2.25 M,which of the following statements is TRUE?

A)the reaction is at equilibrium
B)the forward reaction is spontaneous
C)the reverse reaction is spontaneous
D)the forward reaction is exothermic
E)the reverse reaction is exothermic

Question 61

For the reaction,

What is Δ_rS°?

A)137.4 J/mol ∙ K
B)-137.4 J/mol ∙ K
C)33.8 J/mol ∙ K
D)171.2 J/mol ∙ K
E)-33.8 J/mol ∙ K

Question 62

What is Δ_rG° at 25 °C?
2O₃(g)→ 3 O₂(g)Δ_rH° = -284 kJ Δ_rS° = 139 J/K

A)-145 kJ
B)-243 kJ
C)-325 kJ
D)-281 kJ
E)-287 kJ

Question 63

Calculate the entropy change for methanol at its normal boiling point of 64.5 °C.Δ_rH° = 38.0 kJ/mol.

A)0.589 kJ/mol ∙ K
B)0.112 kJ/mol ∙ K
C)589 kJ/mol ∙ K
D)112 kJ/mol ∙ K
E)0.589 × 10^-2 kJ/mol ∙ K

Question 64

If the enthalpy of vaporization of chloromethane,CH₃Cl,is 21.5 kJ/mol at the normal boiling point,249 K,calculate Δ_vap S°.

A)86.3 J mol^-1 K^-1
B)5.35 J mol^-1 K^-1
C)11.6 J mol^-1 K^-1
D)896 J mol^-1 K^-1

Question 65

What is Δ_rG° at 25 °C?
CO(g)+ 2 H₂(g)→ CH₃OH(g)Δ_rH° = -90.7 kJ Δ_rS° = -221 J/K

A)-90.9 kJ
B)-24.8 kJ
C)-156.6 kJ
D)-96.2 kJ
E)-85.2 kJ

Question 66

Order the following by increasing entropy.
CO(g),COCl₂(g),CO₂(g),CaO(s)

A)CO₂ < CO < CaO < COCl₂
B)CaO < CO < CO₂ < COCl₂
C)COCl₂ < CO < CaO < CO₂
D)CO₂ < CaO < COCl₂ < CO
E)CO < CaO < COCl₂ < CO₂

Question 67

Predict whether ΔS is positive or negative for the following process:
H₂(g)+ 1/2 O₂(g)→ H₂O(g)

A)negative
B)positive
C)ΔS doesn't change.
D)There is not enough information to determine.

Question 68

Consider the following reaction:

What is Δ_rS° in J/mol K?

A)127.6 J/mol K
B)-127.6 J/mol K
C)3.0 J/mol K
D)-258.2 J/mol K
E)-3.0 J/mol K

Question 69

For the reaction

What is D_rS^o?

A)262.5 J/mol ∙ K
B)-85.1 J/mol ∙ K
C)-164.7 J/mol ∙ K
D)164.7 J/mol ∙ K
E)85.1 J/mol ∙ K

Question 70

Consider the following reaction.

What is Δ_rG° for this reaction in kJ?

A)-804
B)-476
C)-386
D)-413
E)-799

Question 71

Consider the following reaction:

What is Δ_rS° for this reaction in J/mol K?

A)-284.6 J/mol K
B)284.6 J/mol K
C)-92.3 J/mol K
D)94.6 J/mol K
E)92.3 J/mol K

Question 72

Consider the following reaction:

What is Δ_rS° for the above reaction in J/mol K?

A)-49.9 J/mol K
B)49.9 J/mol K
C)80.7 J/mol K
D)115.2 J/mol K
E)-80.7 J/mol K

Question 73

What is Δ_rG° at 25 °C?
CO₂(g)→ CO₂(aq)Δ_rH° = -19.4 kJ Δ_rS° = 92.3 J/K

A)2.1 kJ
B)-46.9 kJ
C)-17.1 kJ
D)-19.5 kJ
E)-21.7 kJ

Question 74

Predict whether ΔS is positive or negative for the following process:
H₂O(g)→ H₂O(s)

A)negative
B)positive
C)ΔS doesn't change.
D)There is not enough information to determine.

Question 75

For the reaction


What is D_rS^o?

A)-88.5 J/mol ∙ K
B)-176.7 J/mol ∙ K
C)219 J/mol ∙ K
D)176.7 J/mol ∙ K
E)-219.1 J/mol ∙ K

Question 76

What is Δ_rG° at 25 °C?
CaCO₃(s)→ CaO(s)+ CO₂(g)Δ_rH° = 177.8 kJ Δ_rS° = 160.7 J/K

A)1779 kJ
B)173.8 kJ
C)225.7 kJ
D)181.8 kJ
E)129.9 kJ

Question 77

Which of the listed reactions would couple with the following reaction to produce silver?
Ag₂O(s)→ 2 Ag(s)+ 1/2 O(g)Δ_rG° = 11.2 kJ/mol

A)Ag(s)+ 1/2 Br₂ → AgBr(s)Δ_rG° = 96.9 kJ/mol
B)C + 1/2 O₂ → CO Δ_rG° = -137.2 kJ/mol
C)N + 1/2 O₂ → NO Δ_rG° = 149.3 kJ/mol
D)N + O₂ → NO₂ Δ_rG° = 51.3 kJ/mol
E)C + 2 S → CS₂(l)Δ_rG° = 65.3 kJ/mol

Question 78

Predict whether ΔS is positive or negative for the following process:
2 Cl₂O₇(g)→ 2 Cl₂(g)+ 7 O₂(g)

A)negative
B)positive
C)ΔS doesn't change.
D)There is not enough information to determine.

Question 79

What is Δ_rG° at 25 °C?
N₂O₄(g)→ 2 NO₂(g)Δ_rH° = 58.03 kJ Δ_rS° = 176.7 J/K

A)58.21 kJ
B)62.45 kJ
C)53.6 kJ
D)5.37 kJ
E)111 kJ

Question 80

For the reaction,N₂O₄(g)→ 2 NO₂(g)
S° (J/mol K)304.2 240.0
What is D_rS°?

A)544.2 J/mol ∙ K
B)-64.2 J/mol ∙ K
C)175.8 J/mol ∙ K
D)-175.8 J/mol ∙ K
E)64.2 J/mol ∙ K