Deck 17: Chemical Thermodynamics

Question 1

For which of the following reactions is D H - D E > 0?

A) NaCl (aq) + AgNO₃ (aq)→ AgCl (s) + NaNO₃ (aq)
B) H₂ (g) + Cl₂ (g)→ 2 HCl (g)
C) 2 N₂ (g) + O₂ (g)→ 2 N₂O (g)
D) NH₄NO₃ (s)→ N₂O (g) + 2 H₂O (g)
E) none of these

Answer 1

NH₄NO₃ (s)→ N₂O (g) + 2 H₂O (g)

Question 2

The combustion of a 3.06 g sample of formic acid (H CO₂ H( ), molar mass = 46.03 g/mol) in a bomb calorimeter with a heat capacity of 5.423 J/ C causes the temperature to rise from 23.27 C to 26.41 C. What is D E for the reaction?
2 H CO₂ H ( ) + O₂(g) 2 CO₂ (g) + 2 H₂ O ( )

A) - 5.56 kJ
B) - 17.0 kJ
C) - 256 kJ
D) - 512 kJ
E) none of these

Answer 2

- 512 kJ

Question 3

From the D E given for 25 ° C, calculate D H at the same temperature for the reaction:
2 N₂O (g)→2 N₂ (g) + O₂ (g) D E = - 161.62 kJ

A) - 159.14 kJ
B) - 161.62 kJ
C) - 164.10 kJ
D) - 166.58 kJ
E) none of these

Answer 3

- 164.10 kJ

Question 4

Which of the following units express(es) a quantity of energy?
I. joule
II. L × atm
III. kcal

A) I and III, but not II
B) I and II, but not III
C) I, II, and III
D) I only
E) none of them

Question 5

When a sample of an ideal gas is compressed at 25 ° C from 39.0 L to 15.0 L at a constant pressure of 1.90 atm, the work is

A) w = - 74.1 L × atm
B) w = - 45.6 L × atm
C) w = +28.5 L × atm
D) w = +45.6 L × atm
E) none of these

Question 6

Which of the following statements is incorrect ?

A) For any state function, X, D X = X(final) - X(initial).
B) State functions are path independent.
C) The variables T, V, and P are state functions.
D) The internal energy of a system (E) is a state function.
E) The heat absorbed by a system ( q ) is a state function.

Question 7

Which of the following systems show(s) a decrease in entropy?
The system is underlined.

A) Molten iron solidifies.
B) Ice melts.
C) A jigsaw puzzle is solved.
D) More than one of these is correct.
E) None of these is correct.

Question 8

A sample of an ideal gas at 275 K occupies a volume oF₄2 L. The sample contracts to a volume of 15 L at a constant pressure of 1.50 atm, while heat of 2400 J is lost to the surroundings. What is D E for this process?

A) - 6.5 kJ
B) - 4.1 kJ
C) +1.7 kJ
D) +4.1 kJ
E) none of these

Question 9

The mathematical form of the first law of thermodynamics is:

A) P D V = D nRT
B) D E = q + w
C) D H rxn = D prod = D react
D) D G = D H + T D S
E) none of these

Question 10

One mole of an ideal gas at 300 K expands from 2.0 L to 9.0 L against a constant external pressure of 1.8 atm. The work done by this expansion is (in L × atm):

A) 0
B)
C) - (300)(4.5)(1.8)
D) - (1.8)(9.0 - 2.0)
E)

Question 11

From the D E given for 25 ° C, calculate D H at the same temperature for the reaction:
2 HI (g)→H₂ (g) + I₂ (g) D E = +9.48 kJ

A) +7.00 kJ
B) +9.48 kJ
C) +11.96 kJ
D) +19.39 kJ
E) none of these

Question 12

Which thermodynamic parameter listed below measures the degree of disorder associated with a system?

A) Gibbs Free Energy
B) Enthalpy
C) Entropy
D) Internal energy
E) Work

Question 13

Which substance listed below would be expected to have the greatest entropy value, S ° ?
Assume all substances are in the gas phase at the same temperature.

A) butane
B) ethane
C) methane
D) propane
E) pentane

Question 14

If only work of expansion is done, the heat, q , for a change at constant temperature and volume is equal to what?

A) D E
B) D H
C) D G
D) w
E) none of these

Question 15

When a 3.125 g sample of ammonium nitrate (NH ₄NO₃ , molar mass = 80.05 g/mol) decomposes in a bomb calorimeter with a heat capacity oF₄.116 kJ/ C, the temperature rises from 24.15 C to 25.35 C. What is D E for the decomposition of ammonium nitrate?
NH ₄NO₃(s) N₂O (g) + 2 H₂ O ( )

A) - 126 kJ
B) - 69.5 kJ
C) - 4.94 kJ
D) - 1.58 kJ
E) none of these

Question 16

The combustion of a 0.440 g sample of ethanol (C₂ H₅ OH, molar mass = 46.07 g/mol) in a bomb calorimeter with a heat capacity of 5.278 kJ/ C causes the temperature to rise from 23.98 C to 26.45 C. What is D E for the reaction?
C₂ H₅ OH ( ) + 3 O₂(g) 2 CO₂ (g) + 3 H₂ O ( )

A) - 13.0 kJ
B) - 1.36×10³ kJ
C) - 29.6 kJ
D) +13.0 kJ
E) none of these

Question 17

Which one of the following systems shows a positive entropy change?
The system is underlined.

A) A dormitory room is cleaned.
B) Ice melts.
C) Water freezes.
D) Silver ions react with chloride ions to form AgCl (s).
E) An egg grows into a chick.

Question 18

If q of the system is negative:

A) the surroundings are heated by the system.
B) the bomb-calorimeter reaction is endothermic.
C) D S _univ > 0.
D) PV work is zero.
E) w must also be negative.

Question 19

One mole of a gas, initially at 300 K and 1.00 atm, undergoes a change so the final conditions are T = 400 K and V = 50.0 liters. Which of the following cannot be calculated from this information?

A) q
B) D V
C) D P
D) D T
E) all of these can be found

Question 20

Calculate the work done by 1.00 mol of an ideal gas when it expands from a volume of 14.00 L to a volume of 18.00 L against a constant external pressure of 2.00 atm.

A) w = - 28.0 L × atm
B) w = - 8.00 L × atm
C) w = 0 L × atm
D) w = - 36.0 L × atm
E) w = +28.0 L × atm

Question 21

Which of the following reactions has the largest positive entropy change?

A) PCl 3 (g) + Cl₂ (g) PCl₅ (g)
B) 2 N₂(g) + O₂(g) 2 N₂O (g)
C) 2 NO₂ (g)→ 2 NO (g) + O₂ (g)
D) CO₂ (g)→ O₂ (g) + C (s)
E) H₂ O (g) H₂ O ( )

Question 22

The following reduction of Fe₂ O₃ to Fe occurs in blast furnaces during the steel making process:
3 CO (g) + Fe₂ O₃(s) 2 Fe (s) + 3 CO₂ (g) Calculate per mole of Fe₂ O₃ reacted, if the values of S for CO (g), Fe₂ O₃(s), Fe (s), and CO₂ (g) are 198, 87, 27, and 214 J/mol K, respectively (answer in units of J/K).

A) - 44 J/K
B) - 15 J/K
C) 15 J/K
D) 44 J/K
E) 411 J/K

Question 23

The third law of thermodynamics states that:

A) all spontaneous processes are accompanied by an increase in entropy.
B) the energy of the universe is constant when a physical or chemical change occurs.
C) the free energy change is positive for any spontaneous process.
D) the entropy of a pure crystalline solid is zero at 0 K.
E) heat and work are state functions.

Question 24

For which of the following processes will D S _system be the most positive?

A) H₂ (g) + Cl₂ (g)→ 2 HCl (g)
B) 2 H₂ (g) + O₂(g) 2 H₂ O ( )
C) CaCO₃ (s)→ CaO (s) + CO₂ (g)
D) Ag⁺ (aq) + Cl ^- (aq)→ AgCl (s)
E) KClO₄ (s)→ KCl (s) + 2 O₂ (g)

Question 25

Which of the following physical changes would be expected to have a negative sign for D S _system?
I. Dissolving oxygen gas, O₂, in water.
II. Freezing ice cubes.
III. Breaking glass.

A) I only
B) I and II
C) I and III
D) II and III
E) All of these

Question 26

For the reaction 4 CuO (s)→2 Cu₂O (s) + O₂ (g), what is D S ° at 298 K (in J/K)?
S ° [CuO] = 43 J/mol × K; S ° [O₂] = 205 J/mol × K; S ° [Cu₂O] = 93.14 J/mol × K

A) 0.768 J/K
B) 219 J/K
C) 255 J/K
D) 348 J/K
E) 354 J/K

Question 27

Which of the following chemical equations would be expected to have a positive sign for D S _system?
I. NaClO₃ (s)→Na⁺ (aq) + ClO₃^{1 -} (aq)
II. NH₃ (g) + HBr (g)→NH₄Br (s)
III. H₂S (g) + ¹/₂ O ₂ (g)→¹/₈ S₈ (s) + H₂O (g)

A) I only
B) I and II
C) I and III
D) II and III
E) All of these

Question 28

Which process below is accompanied by a decrease in entropy for the system ?

A) H₂ O ( ) + SOCl₂ ( ) 2 HCl (g) + SO₂ (g)
B) CH₄ (g) + 2 O₂(g) CO₂ (g) + H₂ O ( )
C) H₂O (s)→ H₂O (g)
D) H₂O (g) (420 K)→ H₂O (g) (450 K)
E) none of these

Question 29

Which of the following reactions would be expected to have a positive entropy change , D S > 0?
I. 3 O₂ (g)→2 O₃ (g)
II. CaCO₃ (s)→CaO (s) + CO₂ (g)
III. C₃H₈ (g) + 5 O₂ (g)→3 CO₂ (g) + 4 H₂O (g)

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

Question 30

Which of the following physical changes would be expected to provide a positive change in entropy , D S > 0?
I. Compressing a gas until it liquefies.
II. Melting an ice-cube.
III. Heating a substance to a higher temperature.

A) I only
B) I and II
C) I and III
D) II and III
E) All of these

Question 31

Using the entropy values in the table below, what is the change in standard entropy, D S , for the following reaction?
2 CH₃ OH (g) + 3 O₂(g) 2 CO₂ (g) + 4 H₂ O (g) Substance S (J/mol K) CH₃ OH ( ) 126.8 CH₃ OH (g) 237.6 O₂(g) 205.0 CO₂ (g) 213.6 H₂ O (g) 188.83 H₂ O ( ) 69.91

A) D S ° = - 383.4 J/mol × K
B) D S ° = - 161.8 J/mol × K
C) D S ° = - 40.2 J/mol × K
D) D S ° = 92.3 J/mol × K
E) D S ° = 313.9 J/mol × K

Question 32

"A spontaneous change is always accompanied by an increase in entropy." The entropy change referred to in this statement is:

A) D S _system
B) D S _universe
C) D S _reversible
D) D S _surroundings
E) none of these

Question 33

Which of the following chemical reactions would be expected to have a positive sign for D S _reaction?
I. 2 N₂ (g) + 3 F₂ (g)→2 NF₃ (g)
II. NaCl (aq) + AgNO₃ (aq)→NaNO₃ (aq) + AgCl (s)
III. CaCO₃ (s)→CaO (s) + CO₂ (g)

A) III only
B) I and II
C) I and III
D) II and III
E) All of these

Question 34

Which of the following reactions would be expected to provide a negative change in entropy , D S
I. 2 K (s) + F₂ (g)→2 KF (s)
II. 2 NO₂ (g)→N₂O₄ (g)
III. NaClO₃ (s)→Na⁺ (aq) + ClO₃^{1 -} (aq)

A) I only
B) II only
C) III only
D) I and II
E) All of these

Question 35

Which of the following chemical reactions has the largest positive entropy change?

A) H₂S (g)→ H₂ (g) + S (s)
B) 2 CO₂ (g)→ 2 CO (g) + O₂ (g)
C) 2 Al (s) + 3 O₂ (g)→ 2 Al₂O₃ (s)
D) N₂ (g) + 3 H₂ (g)→ 2 NH₃ (g)
E) 6 CO₂ (g) + 6 H₂O (g)→ C₆H₁₂O₆ (s) + 6 O₂ (g)

Question 36

Which of the following processes would be expected to have a positive sign for D S _system?
I. Hot air expanding.
II. A piece of wax melting.
III. Alcohol evaporating.

A) I only
B) I and II
C) I and III
D) II and III
E) All of these

Question 37

The entropy change when one mole of acetone [(CH₃)₂CO] vaporizes at its boiling point (56 ° C) is D S _vap = 97.16 J/mol × K. How much heat is absorbed when 58.0 grams of acetone vaporizes at 56 ° C?

A) 0.29 kJ
B) 5.44 kJ
C) 97.16 kJ
D) 234 J
E) 32.0 J

Question 38

Which of the following reactions would be expected to have a positive entropy change, D S 0?
I. 2 SO₂ (g) + O₂(g) 2 SO₃(g)
II. Ba(OH) 2 (s) BaO (s) + H₂ O (g)
III. CO (g) + 2 H₂ (g) CH₃ OH ( )

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

Question 39

Which of the following processes results in a negative entropy change?

A) HCN(g, V = 10 L, P = 4 atm) HCN (g, V = 20 L, P = 2 atm)
B) 2 HI (g) H₂ (g) + I₂ (s)
C) NaI (s) NaI ( )
D) CaCO₃(s) CaO (s) + CO₂ (g)
E) Bi ( ) + Sn ( ) + Pb ( ) Soft Solder ( )

Question 40

Estimate the normal boiling point of mercury, given that for Hg ( ), = 0 kJ/mol and D S = 76.02 J/mol K and for Hg (g), = 61.32 kJ/mol and D S = 174.85 J/mol K. The change is:
Hg ( ) Hg (g)

A) 0.62 K
B) 620 K
C) 1.6 K
D) 160 K
E) 1612 K

Question 41

Which of the following processes is(are) considered spontaneous ?
I. Melting ice cubes at - 5 ° C and 1 atm.
II. Alignment of iron fillings in a magnetic field.
III. Formation of CH₄ and O₂ from CO₂ and H₂O at 1 atm and 25 ° C.

A) I only
B) II only
C) III only
D) I and II
E) All of these.

Question 42

The reaction PCl₃ (g) + Cl₂ (g)→PCl₅ (g) is exothermic. The reaction is:

A) spontaneous at all temperatures.
B) nonspontaneous at all temperatures.
C) spontaneous at low temperatures.
D) spontaneous at high temperatures.
E) spontaneous if D G _rxn is positive.

Question 43

Which thermodynamic statement listed below would confirm that a chemical reaction is spontaneous as written?

A) D G < 0
B) D G > 0
C) D S < 0
D) D H > 0
E) D H > 0 and D S < 0

Question 44

What is the criterion for a reaction to be considered spontaneous?

A) D H < 0
B) D H > 0
C) D S > 0
D) D G > 0
E) D G < 0

Question 45

Given the abbreviated table for selected standard molar entropy values of each substance in the reaction below, what is the standard molar change in entropy, D S ° _rxn, for the following reaction?
C₆H₁₂O₆ (s) + 6 O₂ (g)→6 CO₂ (g) + 6 H₂O (g) Substance S ° (Jmol ^{- 1}K ^{- 1}) C₆H₁₂O₆ (s) 212.1 O₂ (g) 205.0 CO₂ (g) 213.7 H₂O (g) 188.7

A) D S ° _rxn = - 14.7 Jmol ^{- 1}K ^{- 1}
B) D S ° _rxn = 972.3 Jmol ^{- 1}K ^{- 1}
C) D S ° _rxn = 1396.5 Jmol ^{- 1}K ^{- 1}
D) D S ° _rxn = 3432.3 Jmol ^{- 1}K ^{- 1}
E) D S ° _rxn = 3856.5 Jmol ^{- 1}K ^{- 1}

Question 46

Given the following data:
2 Cr (s) + ³/₂ O₂ (g)→Cr₂O₃ (s) D G ° = - 100 kJ 2 CrO (s) + O₂ (g)→CrO₃ (s) D G ° = - 50 kJ 2 CrO (s) + ¹/₂ O₂ (g)→Cr₂O₃ (s) D G ° = - 250 kJ Calculate D G ° for:
Cr (s) + ³/₂ O₂ (g)→CrO₃ (s)

A) 50 kJ
B) 25 kJ
C) - 100 kJ
D) - 300 kJ
E) - 400 kJ

Question 47

Exhibit 17-1 Consider the reaction of carbon monoxide and chlorine gas to form phosgene as shown below to answer the following question(s). CO (g) + Cl₂ (g)→ClC(O)Cl (g)
Refer to Exhibit 17-1. What is the standard change in entropy, D S ° _rxn, at 298 K for this reaction given that D G ° _rxn = - 206 kJ/mol and D H ° _rxn = - 220 kJ/mol?

A) D S ° _rxn = - 4.17×10³ Jmol ^{- 1}K ^{- 1}
B) D S ° _rxn = - 1.43×10³ Jmol ^{- 1}K ^{- 1}
C) D S ° _rxn = - 47.0 Jmol ^{- 1}K ^{- 1}
D) D S ° _rxn = - 21.3 Jmol ^{- 1}K ^{- 1}
E) D S ° _rxn = 47.0 Jmol ^{- 1}K ^{- 1}

Question 48

Which substance(s) listed below has(have) a standard molar Gibbs Free Energy of formation, D G f , value equal to 0 kJ/mol?
I. H₂ (g)
II. N₂( )
III. H₂ O ( )

A) I only
B) II only
C) III only
D) I and II
E) All of these

Question 49

Given the abbreviated table for selected standard state entropy values of each substance in the reaction below, what is the value of the standard change in entropy, D S ° , for the following chemical reaction?
3 H₂ (g) + Fe₂O₃ (s)→2 Fe (s) + 3 H₂O (g) Substance S ° (Jmol ^{- 1}K ^{- 1}) H₂ (g) 130.6 Fe (s) 27.3 Fe₂O₃ (s) 87.4 H₂O (g) 188.7

A) D S ° = - 32.5 Jmol ^{- 1}K ^{- 1}
B) D S ° = - 2.0 Jmol ^{- 1}K ^{- 1}
C) D S ° = 141.5 Jmol ^{- 1}K ^{- 1}
D) D S ° = 316.3 Jmol ^{- 1}K ^{- 1}
E) D S ° = 925.1 Jmol ^{- 1}K ^{- 1}

Question 50

Given D = - 371.1 kJ/mol for SO₃ and D = - 300.3 kJ/mol for SO₂ , what is D G for the following reaction?
2 SO₂ (g) + O₂(g) 2 SO₃(g)

A) +141.6 kJ
B) +70.8 kJ
C) - 70.8 kJ
D) - 141.6 kJ
E) not enough information

Question 51

Which substance(s) listed below would be expected to have a standard molar Gibbs Free-Energy of formation equal to zero, D G f = 0?
I. Na + (aq)
II. O₂(g)
III. H₂ O ( )

A) I only
B) II only
C) III only
D) I and II
E) All of these

Question 52

Exhibit 17-1 Consider the reaction of carbon monoxide and chlorine gas to form phosgene as shown below to answer the following question(s). CO (g) + Cl₂ (g)→ClC(O)Cl (g)
Refer to Exhibit 17-1. Given that D S ° _rxn = - 47.0 Jmol ^{- 1}K ^{- 1} and D H ° _rxn = - 220. kJ/mol for this reaction, what is the standard Gibbs Free Energy, D G ° _rxn, for this reaction at 500 K?

A) D G ° _rxn = - 2.37×10⁴ kJ/mol
B) D G ° _rxn = - 243.5 kJ/mol
C) D G ° _rxn = - 196.5 kJ/mol
D) D G ° _rxn = 63.0 kJ/mol
E) D G ° _rxn = 2.33×10⁴ kJ/mol

Question 53

The best measure of the spontaneity of a process is:

A) the change in the number of moles of gaseous species.
B) the change in internal energy of the process.
C) the change in free energy of the process.
D) the change in enthalpy of the process.
E) the change in entropy of the process.

Question 54

Which of the following processes is(are) considered spontaneous ?
I. Melting ice cubes at 5 C and 1 atm.
II. Rust, Fe₂ O₃ , is converted to iron, Fe, and oxygen, O₂.
III. Forming additional NH₃from the following reaction that has previously reached a state of dynamic equilibrium:
N₂(g) + 3 H₂ (g) 2 NH₃(g)

A) I only
B) II only
C) III only
D) I and II
E) All of these.

Question 55

For a given chemical reaction, the value of D H is negative and the value of D S is positive. The value of D G for this reaction indicates that the reaction is:

A) always nonspontaneous.
B) spontaneous only at high temperatures.
C) spontaneous only at low temperatures.
D) spontaneous at all temperatures.
E) nonspontaneous only at high temperatures.

Question 56

Which of the following is true?

A) D E = q - w
B) D G = D E - P D V - T D S
C) D H = D G - T D S
D) D G ° = 0 at 0 K
E) The entropy of the universe is increasing.

Question 57

Given D CuO = - 130 kJ/mol and D Cu 2 O = - 146 kJ/mol, what is D G for the following reaction?
4 CuO (s) 2 Cu 2 O (s) + O₂(g)

A) +298 kJ
B) +228 kJ
C) - 7 kJ
D) - 4 kJ
E) not enough information

Question 58

Which substance(s) listed below would be expected to have a standard Molar Gibbs Free Energy of formation value equal to zero, D G ° _f = 0?
(Pay careful attention to the phase indicators.)

A) H₂ (g)
B) CO₂ (g)
C) NaCl (s)
D) H₂ O ( )
E) All of these.

Question 59

A positive value of D G ° for a reaction indicates that:

A) the reaction favors formation of products.
B) the reaction is spontaneous.
C) the reaction is nonspontaneous.
D) the reaction is at equilibrium.
E) the reaction cannot reach equilibrium.

Question 60

Given the abbreviated table for selected standard molar entropy values of each substance in the reaction below, what is the standard molar change in entropy, D S rxn , for the following reaction?
3 NO₂ (g) + H₂ O ( ) 2 HNO₃( ) + NO (g) Substance S (Jmol - 1 K - 1 ) NO₂ (g) 239.9 H₂ O ( ) 69.94 HNO₃( ) 155.6 NO (g) 210.65

A) D S ° _rxn = - 267.8 Jmol ^{- 1}K ^{- 1}
B) D S ° _rxn = - 127.9 Jmol ^{- 1}K ^{- 1}
C) D S ° _rxn = 56.4 Jmol ^{- 1}K ^{- 1}
D) D S ° _rxn = 1171.6 Jmol ^{- 1}K ^{- 1}
E) D S ° _rxn = 1311.5 Jmol ^{- 1}K ^{- 1}

Question 61

If D H is positive and D S is negative for a particular reaction:

A) the reaction proceeds forward at all temperatures.
B) the reaction proceeds forward at low temperatures.
C) the reaction proceeds forward at high temperatures.
D) the reaction doesn't proceed forward at any temperature.
E) none of these.

Question 62

Consider the following reaction and its corresponding thermodynamic data:
4 KClO₃ (s)→3 KClO₄ (s) + KCl (s) D H ° = - 140 kJ/mol and D S ° = - 45 Jmol ^{- 1}K ^{- 1} At what approximate temperature does this reaction cross-over from being considered spontaneous to being non-spontaneous?

A) It won't cross over. It will always be spontaneous.
B) It won't cross over. It will always be non-spontaneous.
C) 321 K
D) 3111 K
E) 6300 K

Question 63

Exhibit 17-3 Consider the reaction below and its corresponding thermodynamic data to answer the following problem(s). NH₃ (g) + HCl (s)→NH₄Cl (s) D H ° = - 175.9 kJ/mol and D S ° = - 284.6 J/mol × K
Refer to Exhibit 17-3. What is the Standard Gibbs Free Energy change, D G ° , for this reaction at 25 ° C?

A) D G ° = - 261 kJ/mol
B) D G ° = - 183 kJ/mol
C) D G ° = - 169 kJ/mol
D) D G ° = - 91.1 kJ/mol
E) D G ° = 6.94×10³ kJ/mol

Question 64

Consider the following reaction and its corresponding thermodynamic data:
NH₃ (g) + HCl (s)→NH₄Cl (s) D H ° = - 175.9 kJ/mol and D S ° = - 284.6 J/mol × K At what approximate temperature does this reaction cross over from being considered spontaneous to being non-spontaneous?

A) It won't cross over. It will always be spontaneous.
B) It won't cross over. It will always be non-spontaneous.
C) 50.1 K
D) 618 K
E) 1618 K

Question 65

Exhibit 17-5 Consider the reaction of Barium oxide with carbon dioxide to form Barium Carbonate as shown below to answer the following question(s). BaO (s) + CO₂ (g)→BaCO₃ (s) D S ° _rxn = - 174 J/mol × K and D H ° _rxn = - 277 kJ/mol
Refer to Exhibit 17-5. Which statement below is true?

A) This reaction is spontaneous at all temperatures.
B) This reaction is non-spontaneous at all temperatures.
C) This reaction is spontaneous at relatively lower temperatures and non-spontaneous at higher temperatures.
D) This reaction is spontaneous at relatively higher temperatures and non-spontaneous at lower temperatures.
E) There is not enough information to make an assessment.

Question 66

Which of the following conditions describe a reaction that is spontaneous at "high" temperatures and nonspontaneous at low temperatures?

A) D H is ( - ), D S is (+)
B) D H is (+), D S is ( - )
C) D H is (+), D S is (+)
D) D H is ( - ), D S is ( - )
E) All reactions are spontaneous at high temperatures.

Question 67

Exhibit 17-4 Consider the reaction of nitrogen monoxide and oxygen gas to form nitrogen dioxide as shown below to answer the following question(s). NO (g) + O₂ (g)→2 NO₂ (g)
Refer to Exhibit 17-4. Which statement below is correct about the reaction above?

A) This reaction is spontaneous at all temperatures.
B) This reaction is non-spontaneous at all temperatures.
C) This reaction is spontaneous at relatively lower temperatures and non-spontaneous at higher temperatures.
D) This reaction is spontaneous at relatively higher temperatures and non-spontaneous at lower temperatures.
E) There is not enough information to make an assessment.

Question 68

The reaction PCl₃ (g) + Cl₂ (g)→PCl₅ (g) is exothermic. The reaction is:

A) spontaneous at all temperatures.
B) nonspontaneous at all temperatures.
C) spontaneous at low temperatures.
D) spontaneous at high temperatures.
E) spontaneous if D G _rxn is positive.

Question 69

Consider splitting water into hydrogen and oxygen gas and its corresponding thermodynamic data as shown below:
2 H₂ O ( ) 2 H₂ (g) + O₂(g) D S rxn = 326 J/mol K and D H rxn = 572 kJ/mol At what approximate temperature does this reaction cross-over from being considered non-spontaneous to being spontaneous?

A) It won't cross over. It is spontaneous at all temperatures.
B) It won't cross over. It is non-spontaneous at all temperatures.
C) 186 K
D) 570 K
E) 1.75×10³ K

Question 70

Exhibit 17-2 Consider the reaction below and its corresponding thermodynamic data to answer the following problem(s). 3 O₂ (g)→2 O₃ (g) D H ° = 284.6 kJ/mol and D S ° = - 139.8 J/mol × K
Refer to Exhibit 17-2. Which statement below is true regarding this reaction?

A) This reaction is spontaneous at all temperatures.
B) This reaction is spontaneous at relatively lower temperatures and non-spontaneous at higher temperatures.
C) This reaction is spontaneous at relatively higher temperatures and non-spontaneous at lower temperatures.
D) This reaction is non-spontaneous at all temperatures.
E) There is not enough information to make an assessment.

Question 71

The reaction of carbon and water to produce water gas , a mixture of carbon monoxide and hydrogen, is an important industrial reaction. If = +131.3 kJ and = +0.1336 kJ/K for C (s) + H₂ O (g) CO (g) + H₂ (g), determine the temperatures at which this reaction is spontaneous under standard conditions.

A) T > 1.02×10 ^{- 3} K
B) T < 298 K
C) T < 983 K
D) T < 710 K
E) T > 983 K

Question 72

A reaction will proceed spontaneously at any temperature when all reactants and products are present at 1 atm pressure if:

A) D H ° > 0 and D S ° > 0
B) D H ° > 0 and D S ° < 0
C) D H ° D S ° < 0
D) D H ° D S ° > 0
E) none of these

Question 73

For the reaction, PCl₅ (g) PCl 3 (g) + Cl₂ (g), D H = +92.5 kJ and D S = +182 J/K at 25 C. If D H and D S do not change with temperature, this reaction is spontaneous:

A) if T > 0.508 K
B) if T > 508 K
C) if T > 1.93 K
D) if T > 274 K
E) if T < 274 K

Question 74

Exhibit 17-2 Consider the reaction below and its corresponding thermodynamic data to answer the following problem(s). 3 O₂ (g)→2 O₃ (g) D H ° = 284.6 kJ/mol and D S ° = - 139.8 J/mol × K
Refer to Exhibit 17-2. What is the Standard Gibbs Free Energy change, D G ° , for this reaction at 25 ° C?

A) D G ° = 242.9 kJ/mol
B) D G ° = 281.1 kJ/mol
C) D G ° = 288.1 kJ/mol
D) D G ° = 326.3 kJ/mol
E) D G ° = 4.195×10⁴ kJ/mol

Question 75

Exhibit 17-3 Consider the reaction below and its corresponding thermodynamic data to answer the following problem(s). NH₃ (g) + HCl (s)→NH₄Cl (s) D H ° = - 175.9 kJ/mol and D S ° = - 284.6 J/mol × K
Refer to Exhibit 17-3. Which statement below is true regarding this reaction?

A) This reaction is spontaneous at all temperatures.
B) This reaction is spontaneous at relatively lower temperatures and non-spontaneous at higher temperatures.
C) This reaction is spontaneous at relatively higher temperatures and non-spontaneous at lower temperatures.
D) This reaction is non-spontaneous at all temperatures.
E) There is not enough information to make an assessment.

Question 76

Exhibit 17-4 Consider the reaction of nitrogen monoxide and oxygen gas to form nitrogen dioxide as shown below to answer the following question(s). NO (g) + O₂ (g)→2 NO₂ (g)
Refer to Exhibit 17-4. Given that D S ° _rxn = - 146.5 Jmol ^{- 1}K ^{- 1} and D H ° _rxn = - 114.2. kJ/mol for this reaction, what is the standard Gibbs Free Energy, D G ° _rxn, for this reaction at 500 K?

A) D G ° _rxn = 7.31×10⁴ kJ/mol
B) D G ° _rxn = - 41.0 kJ/mol
C) D G ° _rxn = - 89.4 kJ/mol
D) D G ° _rxn = - 187.5 kJ/mol
E) D G ° _rxn = - 203.6 kJ/mol

Question 77

The calculated value of D S is 314.1 J/K for the exothermic reaction:
2 CH₃ OH ( ) + 3 O₂(g) 2 CO₂ (g) + 4 H₂ O (g) Therefore this reaction is:

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

Question 78

The reaction of ammonia and hydrogen chloride produces ammonium chloride as shown:
NH₃ (g) + HCl (g)→NH₄Cl (s) If D H D S < O, then what can be stated about this reaction?

A) This reaction is spontaneous at all temperatures.
B) This reaction is non-spontaneous at all temperatures.
C) This reaction is spontaneous at relatively lower temperatures and non-spontaneous at relatively higher temperatures.
D) This reaction is spontaneous at relatively higher temperatures and non-spontaneous at relatively lower temperatures.

Question 79

Consider the conversion of ozone, O₃, to oxygen, O₂, and this reaction's corresponding thermodynamic data:
2 O₃ (g)→3 O₂ (g) D H ° = - 286 kJ/mol and D S ° = 137 Jmol ^{- 1}K ^{- 1} At what approximate temperature does this reaction cross-over from being considered spontaneous to being non-spontaneous?

A) It won't cross over. It will always be spontaneous.
B) It won't cross over. It will always be non-spontaneous.
C) 149 K
D) 208 K
E) 479 K

Question 80

Exhibit 17-5 Consider the reaction of Barium oxide with carbon dioxide to form Barium Carbonate as shown below to answer the following question(s). BaO (s) + CO₂ (g)→BaCO₃ (s) D S ° _rxn = - 174 J/mol × K and D H ° _rxn = - 277 kJ/mol
Refer to Exhibit 17-5. What is the standard molar Gibbs Free Energy, D G ° _rxn, for this reaction at 500 K?

A) D G ° _rxn = - 365 KJ/mol
B) D G ° _rxn = - 313 KJ/mol
C) D G ° _rxn = - 226 KJ/mol
D) D G ° _rxn = - 190 KJ/mol
E) D G ° _rxn = - 35 KJ/mol