Deck 18: Thermodynamics and Equilibrium

Question 1

What is the change in internal energy of the system (ΔU)if 82 kJ of heat energy is absorbed by the system and 40 kJ of work is done on the system for a certain process?

A)122 kJ
B)42 kJ
C)82 kJ
D)-122 kJ
E)-42 kJ

Answer 1

122 kJ

Question 2

The enthalpy of vaporization (ΔH°_vap)of benzene is 30.7 kJ/mol at its normal boiling point of 353.3 K.What is ΔS°_vap at this temperature?

A)86.9 J/(mol·K)
B)0.087 J/(mol·K)
C)11.5 J/(mol·K)
D)0.0115 J/(mol·K)
E)383 J/(mol·K)

Answer 2

86.9 J/(mol·K)

Question 3

Which of the following is true for the condensation of a gaseous substance?

A)ΔS = 0 and ΔH = 0.
B)​ΔS > 0 and ΔH > 0.
C)ΔS < 0 and ΔH > 0.
D)ΔS < 0 and ΔH < 0.
E)ΔS > 0 and ΔH < 0.

Answer 3

ΔS < 0 and ΔH < 0.

Question 4

The standard enthalpy of vaporization of Freon-11,CFCl₃,is 25.21 kJ/mol at its normal boiling point of 17°C.What is the change of entropy for 1 mol of liquid Freon-11 when it vaporizes at its normal boiling point?

A)8.69 × 10^-2 J/K
B)7.31 × 10³ J/K
C)86.9 J/K
D)1.48J/K
E)1.48× 10³ J/K

Question 5

The standard enthalpy of fusion of iodobenzene is 9.75 kJ/mol at its melting point,241.8 K.What is the standard change in entropy for the melting of iodobenzene at its melting point?

A)0.0189 J/(mol ∙ K)
B)40.3 J/(mol ∙ K)
C)9.75 J/(mol ∙ K)
D)311 J/(mol ∙ K)
E)0.0403 J/(mol ∙ K)

Question 6

The total entropy of a system and its surroundings always increases for a spontaneous process.This is a statement of

A)the third law of thermodynamics.
B)the law of constant composition.
C)the second law of thermodynamics.
D)the law of conservation of matter.
E)the first law of thermodynamics.

Question 7

Assuming ΔH and ΔS are constant with respect to temperature,under what conditions will a chemical reaction be spontaneous at all temperatures?

A)ΔH is negative,and ΔS is positive.
B)ΔH is positive,and ΔS is negative.
C)ΔS = 0,and ΔH is positive.
D)ΔH = 0,and ΔS is negative.
E)none of these

Question 8

For the isothermal (constant-temperature)expansion of an ideal gas,

A)w > 0 and q < 0.
B)w = 0 and q > 0.
C)w < 0 and q = 0.
D)w < 0 and q > 0.
E)w > 0 and q > 0.

Question 9

Which of the following compounds has the highest standard entropy per mole at 298 K?

A)H₂O(l)
B)CaCO₃(s)
C)CO(g)
D)SiO₂(s)
E)CH₃OH(l)

Question 10

In which of the following scenarios is no change in the internal energy of the system possible?

A)​​q < 0,​w > 0​
B)q > 0,w > 0
C)q = 0,w > 0
D)q < 0,w = 0
E)q < 0,w < 0

Question 11

A gas absorbs 0.0 J of heat and then performs 99.5 J of work.What is the change in internal energy of the gas?

A)-99.5 J
B)59.5 J
C)139.5 J
D)99.1 J
E)none of these

Question 12

For a particular process,q = 20 kJ and w = 15 kJ.Which of the following statements is true?

A)ΔU = 35 kJ.
B)The system does work on the surroundings.
C)Heat flows from the system to the surroundings.
D)All of the above are true.
E)None of the above are true.

Question 13

Which of the following is not a state function?

A)w
B)H
C)P
D)U
E)T

Question 14

The standard enthalpy of vaporization of methanol is 35.2 kJ/mol at its normal boiling point,64.6°C.What is the standard change in entropy for the vaporization of methanol at its normal boiling point?

A)104 J/(mol ∙ K)
B)35.2 J/(mol ∙ K)
C)0.544 J/(mol ∙ K)
D)0.104 J/(mol ∙ K)
E)544 J/(mol ∙ K)

Question 15

A system under constant external pressure undergoes a decrease in volume.What is the effect on the surroundings?

A)Energy is transferred as pressure-volume work done by the surroundings on the system.
B)Energy is transferred as pressure-volume work done on the surroundings.
C)Energy is transferred as heat from the system to the surroundings.
D)Energy is transferred as heat from the surroundings to the system.
E)None of the above.

Question 16

According to the first law of thermodynamics,the energy of the universe is constant.Does this mean that ΔE is always equal to zero?

A)No,ΔE does not always equal zero,but this is due only to factors such as friction and heat.
B)No,ΔE never equals zero because energy is always flowing between the system and the surroundings.
C)No,ΔE does not always equal zero because it refers to the system's internal energy,which is affected by heat and work.
D)Yes,ΔE = 0 at all times,which is why q = -w.
E)No,ΔE never equals zero because work is always being done on the system or by the system.

Question 17

Which of the following has the lowest entropy per mole?

A)liquid sodium at 100°C
B)gaseous sodium at 900°C and 0.5 atm
C)a solid solution of sodium in potassium at 30°C
D)gaseous sodium at 900°C and 1 atm
E)solid sodium at 30°C

Question 18

At the normal boiling point of benzene,ΔH°_vap = 30.7 kJ/mol and ΔS°_vap = 86.9 J/(mol ∙ K).What is the normal boiling point of benzene?

A)267 K
B)373 K
C)115 K
D)869 K
E)353 K

Question 19

ΔH and ΔU are nearly the same in all the following processes except

A)F₂(g)+ H₂(g)→ 2HF(g).
B)CH₄(g)+ Cl₂(g)→ CH₃Cl(g)+ HCl(g).
C)C₆H₆(s)→ C₆H₆(l).
D)CuO(s)+ H₂(g)→ Cu(s)+ H₂O(g).
E)3O₂(g)→ 2O₃(g).

Question 20

What is the change in internal energy (ΔU)of the system if q = -8 kJ and w = -1 kJ for a certain process?

A)-9 kJ
B)-7 kJ
C)7 kJ
D)9 kJ
E)-8 kJ

Question 21

For which of the following reactions is ΔS° at 25°C closest to zero?

A)N₂(g)+ O₂(g)→ 2NO(g)
B)H₂(g)+ I₂(s)→ 2HI(g)
C)CH₃CHO(g)+ ⁵/₂O₂(g)→ 2CO₂(g)+ 2H₂O(g)
D)2NO(g)+ O₂(g)→ 2NO₂(g)
E)C₂H₄(g)+ Br₂(l)→ C₂H₄Br₂(l)

Question 22

For the reaction N₂(g)→ 2N(g),

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

Question 23

For the process Cl₂(g)→ 2Cl(g),

A)ΔH is + and ΔS is + for the reaction.
B)ΔH is + and ΔS = 0 for the reaction.
C)ΔH is - and ΔS is - for the reaction.
D)ΔH is - and ΔS is + for the reaction.
E)ΔH is + and ΔS is - for the reaction.

Question 24

For which of the following reactions is ΔS° > 0 at 25°C?

A)2H₂(g)+ O₂(g)→ 2H₂O(g)
B)2ClBr(g)→ Cl₂(g)+ Br₂(g)
C)I₂(g)→ I₂(s)
D)2NO(g)+ O₂(g)→ 2NO₂(g)
E)NH₄HS(s)→ NH₃(g)+ H₂S(g)

Question 25

What is the thermodynamic quantity that provides the criterion for the spontaneity of a chemical reaction?

A)TΔS
B)ΔU
C)ΔS
D)ΔG
E)ΔH

Question 26

The third law of thermodynamics states that

A)the entropy of the universe is increasing.
B)the entropy of the universe is constant.
C)the entropy of the universe equals the sum of the entropy of system and that of the surroundings.
D)the absolute entropy of a substance decreases with increasing temperature.
E)the entropy is zero at 0 K for a perfect crystal.

Question 27

Which of the following equations is correct?

A)G = S - TH
B)G = H - PV
C)G = H - TS
D)ΔG = G_initial - G_final
E)G = S - PV

Question 28

What is the change in entropy when 0.802 g of silicon is burned in excess oxygen to yield silicon dioxide at 298 K?
Si(s)+ O₂(g)→ SiO₂(s); ΔS° = -182.4 J/K at 298 K

A)182J/K
B)146 J/K
C)-1.75 × 10^-2 J/K
D)-6.39 × 10³ J/K
E)5.2 J/K

Question 29

In which reaction is ΔS° expected to be negative?

A)2C₂H₆(g)+ 7O₂(g)→ 4CO₂(g)+ 6H₂O(l)
B)Ga(l)→ Ga(s)
C)H₂O(l)+ 2SO₂(g)→ H₂SO₄(l)
D)CO₂(g)→ CO₂(s)
E)all of above

Question 30

Given the following,determine S° at 298 K for one mole of NO(g).
2NO(g)+ O₂(g)→ 2NO₂(g); ΔS° = −146.7 J/K at 298K

A)210.9 J/K
B)−90.85 J/K
C)421.7 J/K
D)-421.7 J/K
E)+90.85 J/K

Question 31

Which of the following reactions has the smallest value of ΔS° at 25°C?

A)C₆H₆(l)+ ⁹/₂O₂(g)→ 6CO(g)+ 3H₂O(g)
B)C₆H₆(s)→ C₆H₆(l)
C)C₆H₆(l)+ Br₂(l)→ C₆H₅Br(l)+ HBr(g)
D)C₆H₆(s)→ C₆H₆(g)
E)C₆H₆(l)+ ¹⁵/₂O₂(g)→ 6CO₂(g)+ 3H₂O(g)

Question 32

The free-energy change of a reaction is a measure of

A)the excess entropy given off to the reaction system.
B)the increased molecular disorder that occurs in the system.
C)the energy given off to the surroundings.
D)the direction in which a net reaction occurs.
E)the excess entropy given off to the surroundings.

Question 33

For which of the following reactions is ΔS° < 0 at 25°C?

A)2KClO₃(s)→ 2KCl(s)+ 3O₂(g)
B)2HgO(s)→ 2Hg(l)+ O₂(g)
C)Br₂(l)→ Br₂(g)
D)P₄(s)+ 5O₂(g)→ P₄O₁₀(s)
E)(NH₄)₂Cr₂O₇(s)→ N₂(g)+ 4H₂O(l)+ Cr₂O₃(s)

Question 34

What is the change in entropy when 7.61 mL of liquid benzene (C₆H₆,d = 0.879 g/mL)is combusted in the presence of 22.3 L of oxygen gas,measured at 298 K and 1 atm pressure? (R = 0.0821 L · atm/(K · mol))
2C₆H₆(l)+ 15O₂(g)→ 12CO₂(g)+ 6H₂O(l); ΔS° = -437.7 J/K at 298 K

A)398 J/K
B)45.3 J/K
C)37.4 J/K
D)18.7 J/K
E)436 J/K

Question 35

What is the change in entropy when 0.517 g of water decomposes to form hydrogen gas and oxygen gas at 298 K?
2H₂O(l)→ 2H₂(g)+ O₂(g); ΔS° = 326.3 J/K at 298 K

A)4.68 J/K
B)0.0628 J/K
C)18.7 J/K
D)9.36 J/K
E)168 J/K

Question 36

Which of the following is the best criterion for determining the spontaneity of a chemical reaction?

A)ΔH
B)ΔH°
C)ΔG
D)ΔG°
E)TΔS

Question 37

Which of the following is not a spontaneous process at 25°C and 1 atm pressure?

A)salt dissolving
B)ice melting
C)water boiling
D)iron rusting
E)steam condensing

Question 38

For which of the following reactions is ΔS° > 0 at 25°C?

A)MgO(s)+ CO₂(g)→ MgCO₃(s)
B)2H₂(g)+ O₂(l)→ 2H₂O(l)
C)2Li(s)+ O₂(g)→ Li₂O(s)
D)2CO(g)+ O₂(g)→ 2CO₂(g)
E)F₃BNH₃(s)→ BF₃(g)+ NH₃(g)

Question 39

For which of the following processes would ΔS° be expected to be most positive?

A)H₂O(l)→ H₂O(s)
B)NH₃(g)+ HCl(g)→ NH₄Cl(s)
C)O₂(g)+ 2H₂(g)→ 2H₂O(g)
D)N₂O₄(g)→ 2NO₂(g)
E)2NH₄NO₃(s)→ 2N₂(g)+ O₂(g)+ 4H₂O(g)

Question 40

Which of the following reactions has the largest positive value of ΔS° per mole of O₂ at 25°C?

A)2H₂(g)+ O₂(g)→ 2H₂O(g)
B)2C(s)+ O₂(g)→ 2CO(g)
C)2Mg(s)+ O₂(g)→ 2MgO(s)
D)C(s)+ O₂(g)→ CO₂(g)
E)2NO(g)+ O₂(g)→ 2NO₂(g)

Question 41

Based on the following data,what is the standard Gibbs free energy of formation of the sulfate ion at 298 K? (R = 8.31 J/(K ∙ mol))
PbSO₄(s) Pb²⁺(aq)+ SO₄^2-(aq); K_sp = 1.7 × 10^-8

A)-788.6 kJ/mol
B)-793.1 kJ/mol
C)-837.4 kJ/mol
D)-744.3 kJ/mol
E)832.9 kJ/mol

Question 42

Consider the following reaction:
CaO(s)+ CO₂(g)→ CaCO₃(s); ΔG° = -130.9 kJ at 298 K
At what partial pressure of CO₂(g)will the reaction no longer be spontaneous at 298 K? (R = 0.0821 L ∙ atm/(K ∙ mol)= 8.31 J/(K ∙ mol))

A)1.59 × 10⁸ atm
B)1.00 atm
C)6.28 × 10^-9 atm
D)8.77 × 10²² atm
E)1.14 × 10^-23 atm

Question 43

For a reaction system that is at equilibrium,which of the following must always be true?

A)ΔH = 0
B)ΔS = 0
C)ΔG = 0
D)q = 0
E)ΔU = 0

Question 44

Given the following,determine ΔG°_f at 298 K for SnO.
Sn(s)+ SnO₂(s)→ 2SnO(s); ΔG° = 12.0 kJ at 298K

A)-251.9 kJ/mol
B)-503.8 kJ/mol
C)527.8 kJ/mol
D)263.9 kJ/mol
E)1055.6 kJ/mol

Question 45

For which of the following substances is the standard free energy of formation not equal to zero at 298 K?

A)Xe(g)
B)2.7182818285(s)
C)H₂(g)
D)Ca(g)
E)Zn(s)

Question 46

Determine ΔG° for the following reaction:
CH₄(g)+ 2O₂(g)
CO₂(g)+ 2H₂O(l)

A)-581.2 kJ
B)-818.6 kJ
C)131.1 kJ
D)-682.5 kJ
E)-919.9 kJ

Question 47

What is ΔS° at 298 K for the following reaction?
CH₄(g)+ N₂(g)→ HCN(g)+ NH₃(g); ΔH° = 164.1 kJ; ΔG° = 159.1 kJ at 298 K

A)2.0 J/K
B)5.5 × 10² J/K
C)1.1 × 10³ J/K
D)5.3 × 10² J/K
E)17 J/K

Question 48

Which of the following is correct for the condensation of gaseous ammonia at -38°C? The normal boiling point of ammonia is -33°C.

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

Question 49

-Given the following,determine ΔG° at 298 K for the precipitation reaction,
Ag⁺(aq)+I−(aq)→ AgI(s)

A)-91.7 kJ/mol
B)-40.7 kJ/mol
C)91.7 kJ/mol
D)40.7 kJ/mol
E)62.5 kJ/mol

Question 50

Consider the following hypothetical reaction at 310 K.Standard free energies of formation are given in parentheses.
B C ΔG° = -25.0kJ/mol
(?) (176.4 kJ/mol)
Calculate the standard free energy of formation of compound B.

A)151.4 kJ/mol
B)-201.4 kJ/mol
C)-151.4kJ/mol
D)201.4 kJ/mol
E)none of these

Question 51

oWhat is the change in free energy at 298 K when 70.0 mL of 0.704 M calcium chloride is combined with 47.9 mL of 0.859 M sodium carbonate? (R = 8.31 J/(K ∙ mol))
Ca²⁺(aq)+ CO₃^2-(aq)→ CaCO₃(s)

A)42.6 kJ
B)-2.21 × 10³ kJ
C)46.1 kJ
D)47.4 kJ
E)2.56 × 10³ kJ

Question 52

Which of the following is true for the reaction NH₃(l) NH₃(g)at -33°C and 1 atm pressure? (The normal boiling point for NH₃ is -33°C.)

A)ΔH = TΔS
B)ΔH = 0
C)ΔH = ΔnRT
D)ΔS = 0
E)ΔH = PΔV

Question 53

For a certain process,at 300.K,ΔG = -37.2 kJ and ΔH = -7.0 kJ.If the process is carried out reversibly,what is the amount of useful work that can be performed?

A)-7.0 kJ
B)-44.2 kJ
C)-30.2 kJ
D)30.2 kJ
E)-37.2 kJ

Question 54

What is ΔG° at 298 K for the following reaction?
H₂(g)+ Br₂(g)→ 2HBr(g); ΔH° = -103.8 kJ; ΔS° = 21.3 J/K at 298 K

A)97.45 kJ
B)111 kJ
C)110.1 kJ
D)6.451 × 10³ kJ
E)-6.451× 10³ kJ

Question 55

For a reversible phase change at constant temperature and pressure,

A)ΔG = 0.
B)ΔU = 0.
C)w = 0.
D)ΔH = 0.
E)q = 0.

Question 56

If a process is both endothermic and spontaneous,then

A)ΔH = 0.
B)ΔG > 0.
C)ΔS > 0.
D)ΔU < 0.
E)ΔH < 0.

Question 57

Which of the following has a value of zero for the standard free energy of formation at 298 K?

A)I(l)
B)I₂(g)
C)I₂(l)
D)I₂(s)
E)I(g)

Question 58

An ideal fuel for the control jet of a space vehicle should decompose with

A)ΔG = 0 and ΔH = 0.
B)ΔG < 0 and ΔH < 0.
C)ΔG > 0 and ΔH > 0.
D)ΔG < 0 and ΔH > 0.
E)ΔG > 0 and ΔH < 0.

Question 59

From these two reactions at 298 K,
V₂O₃(s)+ 3CO(g)→ 2V(s)+ 3CO₂(g); ΔH° = 369.8 kJ; ΔS° = 8.3 J/K
V₂O₅(s)+ 2CO(g)→ V₂O₃(s)+ 2CO₂(g); ΔH° = -234.2 kJ; ΔS° = 0.2 J/K
Calculate ΔG° for the following at 298 K:
2V(s)+ 5CO₂(g)→ V₂O₅(s)+ 5CO(g)

A)+133.1 kJ
B)+601.6 kJ
C)-601.6 kJ
D)-133.1 kJ
E)+1.6 kJ

Question 60

Given the following,determine K at 298K for the reaction,
AgI(s)→ Ag⁺(aq)+I−(aq)

A)
B)
C)
D)
E)

Question 61

A 0.0333 M solution of a particular weak base,B,has a pH of 8.30 at 298 K.What is ΔG° for the following equilibrium?
B(aq)+ H₂O(l) BH⁺(aq)+ OH^-(aq)

A)32.5 kJ
B)47.3 kJ
C)8.42 kJ
D)56.5 kJ
E)86.2 kJ

Question 62

A certain reaction has negative values for both ΔH and ΔS.Therefore,the reaction

A)can be spontaneous if the temperature is low enough.
B)cannot be spontaneous at any temperature.
C)must be spontaneous at all temperatures.
D)can be spontaneous if the temperature is high enough.
E)has a positive free energy at any temperature.

Question 63

For a reaction,if ΔG° = 0,then

A)ΔS° = 0.
B)K = 0.
C)ΔH° = 0.
D)K = 1.
E)ΔG = 0.

Question 64

Consider the following hypothetical reaction (at 316.8 K).Standard free energies,in kJ/mol,are given in parentheses.
A B+C
ΔG° = ?
(-32.2)
(207.8)
(-237.0)
What is the value of the equilibrium constant for the reaction at 316.8 K?

A)0.42
B)1.0
C)273
D)6.5× 10⁴
E)0.32

Question 65

For the reaction 2SO₂(g)+ O₂(g)→ 2SO₃(g),ΔH° and ΔS° are both negative at 298 K,and the process is spontaneous at 298 K.Which of the following statements must also be true?

A)The change in entropy is the driving force of the reaction.
B)ΔG is positive for the reaction at 298 K.
C)The direction of the reaction may be reversed at high temperatures.
D)ΔG is temperature independent.
E)At high temperature,ΔH becomes positive.

Question 66

For the reaction MgSO₃(s)→ MgO(s)+ SO₂(g),which is spontaneous only at high temperatures,one would predict that

A)ΔH is negative and ΔS is negative at room temperature.
B)ΔH is positive and ΔS is positive at room temperature.
C)ΔH is positive and ΔS is negative at room temperature.
D)ΔG is positive at high temperatures.
E)ΔH is negative and ΔS is positive at room temperature.

Question 67

The following reaction is spontaneous at all temperatures:
CaC₂(s)+ 2H₂O(l)→ Ca(OH)₂(s)+ C₂H₂(g)
Which of the following statements is true?

A)ΔH is negative and ΔS is positive.
B)ΔH is negative and ΔS is negative.
C)ΔH is positive and ΔS is negative.
D)ΔH is positive and ΔS is positive.
E)ΔG is positive at all temperatures.

Question 68

The reaction Br₂(g)→ 2Br(g)is spontaneous only at temperatures in excess of 1600°C.We can conclude that

A)ΔH is + and ΔS is + for the reaction.
B)ΔH is - and ΔS is + for the reaction.
C)ΔG is + for all temperatures.
D)ΔH is - and ΔS is - for the reaction.
E)ΔH is + and ΔS is - for the reaction.

Question 69

A 0.0835 M solution of a particular monoprotic weak acid,HA,has a pH of 5.00 at 298 K.What is ΔG° for the following equilibrium?
HA(aq)+ H₂O(l) H₃O⁺(aq)+ A^-(aq)

A)22.3 kJ
B)28.5 kJ
C)502 kJ
D)6.14 kJ
E)50.8 kJ

Question 70

For the reaction 4Ag(s)+ O₂(g)→ 2Ag₂O(s),ΔH° = -61.14 kJ and ΔS° = -132 J/K at 25°C.Which of the following statements is true? Assume that ΔH° and ΔS° are essentially temperature independent.

A)The change in entropy is the driving force at low temperatures.
B)The reaction will be spontaneous at high temperatures,and the reverse reaction will be spontaneous at low temperatures.
C)The reaction will not be spontaneous at any temperature.
D)The reaction will be spontaneous at low temperatures,and the reverse reaction will be spontaneous at high temperatures.
E)The reaction will be spontaneous at all temperatures.

Question 71

What is ΔG° at 298 K for the following equilibrium?
Ag⁺(aq)+ 2NH₃(aq) Ag(NH₃)₂⁺(aq); K_f = 1.7 × 10⁷ at 298 K

A)-41 kJ
B)41 kJ
C)-18 kJ
D)0
E)18 kJ

Question 72

For a reaction that has an equilibrium constant of 6 × 10⁹,which of the following statements must be true?

A)ΔS° is positive.
B)ΔG° is negative.
C)ΔG° is positive.
D)ΔH° is negative.
E)ΔH° is positive.

Question 73

A certain reaction is found to be reactant favored.Which of the following is a correct description of the reaction?

A)ΔG° > 0,K < 1
B)ΔG° < 0,K > 1
C)ΔG° > 0,K > 1
D)ΔG° < 0,K < 1
E)ΔG° = 0,K < 1

Question 74

The standard free energy of formation of nitric oxide,NO,at 1000.K (roughly the temperature in an automobile engine during ignition)is 77.7 kJ/mol.Calculate the equilibrium constant for the reaction
2NO(g)
At 1000.K.(R = 8.31 J/(K ∙ mol))

A)0.95
B)7.6 × 10^-9
C)1.6 × 10⁵
D)-15
E)8.7 × 10^-5

Question 75

For the reaction CaCO₃(s)→ CaO(s)+ O₂(g)at 1 atm pressure,the values of ΔH and ΔS are both positive,and the process is spontaneous at high temperatures.Which of the following statements about this reaction is true?

A)The change in entropy is the driving force for the reaction.
B)The process is exothermic at high temperatures and endothermic at room temperature.
C)The reverse reaction is endothermic.
D)The reverse reaction is nonspontaneous at room temperature.
E)ΔG at room temperature is negative.

Question 76

The reaction CaO(s)+ SO₃(g)→ CaSO₄(s)is nonspontaneous at 2200 K,whereas it is spontaneous at room temperature.Which of the following statements is false?

A)The change in enthalpy is the main driving force of the reaction.
B)Both ΔH and ΔS are negative for the reaction.
C)ΔG is negative at room temperature.
D)The change in entropy is the main driving force of the reaction.
E)ΔG becomes zero at a temperature between 300 and 2200 K.

Question 77

Water gas,a commercial fuel,is made by the reaction of hot coke carbon with steam:
When equilibrium is established at 832°C,the concentrations of CO,H₂,and H₂O are 4.00 × 10^-2,4.00 × 10^-2,and 1.00 × 10^-2 mol/L,respectively.Calculate the value of ΔG° for this reaction at 832°C.

A)55.0 kJ
B)12.7 kJ
C)16.8 kJ
D)-12.7 kJ
E)none of these

Question 78

Consider the following reaction:
2AgCl(s)→ 2Ag(s)+ Cl₂(g); ΔH° = 127.1 kJ; ΔS° = 115.7 J/K at 298 K
Suppose 61.4 g of silver(I)chloride is placed in a 50.0 L vessel at 298 K.What is the equilibrium partial pressure of chlorine gas? (R = 0.0821 L ∙ atm/(K ∙ mol)= 8.31 J/(K ∙ mol))

A)0.100 atm
B)5.1 × 10^-23 atm
C)0.950 atm
D)0.210 atm
E)5.7 × 10^-17 atm

Question 79

What is ΔG° at 500.0 K for the following reaction?
Zn(s)+ H₂O(g)→ ZnO(s)+ H₂(g)

A)80.7 kJ
B)-80.7 kJ
C)92.0 kJ
D)-92.0 kJ
E)-136.7 kJ

Question 80

Consider the following reaction:
2C(s)+ 2H₂(g)→ C₂H₄(g); ΔH° = 52.47 kJ; ΔS° = -53.5 J/K at 298 K
What is the equilibrium constant at 298 K for this reaction?

A)1.0 × 10^-12
B)1.0
C)1.6 × 10^-3
D)9.8 × 10¹¹
E)6.4 × 10^-10