Deck 19: Thermodynamics

Question 1

The mathematical equation that expresses the first law of thermodynamics is

A) $\Delta$ H = $\Delta$ E + p $\Delta$ V.
B) $\Delta$ H = $\Delta$ E - p $\Delta$ V.
C) $\Delta$ H = q + w.
D) $\Delta$ E = q + w.
E) $\Delta$ H = q + $\Delta$ E.

Answer 1

$\Delta$ E = q + w.

Question 2

The standard enthalpy of reaction, $\Delta$ H°_rxn for C₂H₂(g)+ 2 H₂(g) $\rarr$ C₂H₆(g)is -311.5 kJ mol^-1. Determine the value of $\Delta$ E°_rxn for this reaction.

A)-306.5 kJ mol^-1
B)-309.0 kJ mol^-1
C)-314.0 kJ mol^-1
D)-316.46 kJ mol^-1
E)+4646 kJ mol^-1

Answer 2

-306.5 kJ mol^-1

Question 3

The standard enthalpy of reaction, $\Delta$ H° at 25 C° NH₃(g)+ HCl(g) $\rarr$ NH₄Cl(s)is -175.9 kJ mol^-1. Determine the value of $\Delta$ E°_rxn for this reaction.

A)-164.8 kJ mol^-1
B)-170.9 kJ mol^-1
C)-173.4 kJ mol^-1
D)-180.9 kJ mol^-1
E)+5134 kJ mol^-1

Answer 3

-170.9 kJ mol^-1

Question 4

The standard enthalpy of reaction, $\Delta$ H°_rxn, for the reaction,C₄H₁₀(g)+ 13/2 O₂(g) $\rarr$ 4 CO₂(g)+ 5 H₂O(l)is -2877 kJ mol^-1. Determine the value of $\Delta$ E°_rxn for this reaction.

A)-2868 kJ mol^-1
B)-2871 kJ mol^-1
C)-2880 kJ mol^-1
D)-2886 kJ mol^-1
E)+2886 kJ mol^-1

Question 5

The standard enthalpy of reaction, $\Delta$ H°_rxn, for the reaction,CaO(s)+ SO₃(g) $\rarr$ CaSO₄(s)is -401.5 kJ mol^-1. Determine the value of $\Delta$ E°_rxn for this reaction.

A)-362.2 kJ mol^-1
B)-399.0 kJ mol^-1
C)-404.0 kJ mol^-1
D)-2880 kJ mol^-1
E)+2077 kJ mol^-1

Question 6

Which statement is true?

A)Spontaneous changes are always accompanied by an increase in the entropy of the system.
B)Spontaneous changes are always accompanied by a decrease in the entropy of the system.
C)Spontaneous changes are always accompanied by an increase in the enthalpy of the system.
D)Spontaneous changes are always accompanied by a decrease in the enthalpy of the system.
E)Most highly exothermic chemical reactions are also spontaneous chemical reactions.

Question 7

Which process is accompanied by an increase in entropy?

A)setting up a stack of dominos
B)setting up decorations on a Christmas tree
C)filing correspondence in file folders and placing them in hanging file folders
D)dropping a glass pane on the front walk of your residence
E)restocking a canned goods shelf display in a supermarket

Question 8

Which reaction is accompanied by an increase in entropy?

A)ZnS(s)+ 3/2 O₂(g) $\rarr$ ZnO(s)+ SO₂(g)
B)CH₄(g)+ H₂O(g) $\rarr$ CO(g)+ 3H₂(g)
C)BaO(s)+ CO₂(g) $\rarr$ BaCO₃(s)
D)Na₂CO₃(s)+ CO₂(g)+ H₂O(g) $\rarr$ 2 NaHCO₃(s)
E)N₂(g)+ 3 H₂(g) $\rarr$ 2 NH₃(g)

Question 9

Which reaction is accompanied by an increase in entropy?

A)2 H(g) $\rarr$ H₂(g)
B)NiCl₂(s)+ 6 NH₃(g) $\rarr$ NiCl₂?6NH₃(s)
C)I₂(g) $\rarr$ 2 I(g)
D)ZnO(s)+ CO₂(g) $\rarr$ ZnCO₃(s)
E)C₂H₄(g)+ Cl₂(g) $\rarr$ C₂H₄Cl₂(l)

Question 10

Which reaction is accompanied by an increase in entropy?

A)C₁₂H₂₀(l)+ 17 O₂(g) $\rarr$ 12 CO₂(g)+ 10 H₂O(l)
B)NH₄Cl(s) $\rarr$ NH₃(g)+ HCl(g)
C)2 C₂H₂(g)+ 5 O₂(g) $\rarr$ 4 CO₂(g)+ 2 H₂O(s)
D)Ba(OH)₂(s)+ 2 HCl(g) $\rarr$ BaCl₂.2H₂O(s)
E)(CH₃)₂CO(l)+ 4 O₂(g) $\rarr$ 3 CO₂(g)+ 3 H₂O(l)

Question 11

Which reaction is accompanied by an increase in entropy?

A)C₈H₁₆(l)+ 12 O₂(g) $\rarr$ 8 CO₂(g)+ 8 H₂O(l)
B)N₂(g)+ 3 H₂(g) $\rarr$ 2 NH₃(g)
C)2 C₂H₂(g)+ 5 O₂(g) $\rarr$ 4 CO₂(g)+ 2 H₂O(s)
D)Ba(OH)₂(s)+ CO₂(g) $\rarr$ BaCO₃(s)+ H₂O(l)
E)NH₄NO₂(s) $\rarr$ N₂(g)+ 2 H₂O(l)

Question 12

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

A)the mixing of one liter of water with one liter of ethylene glycol to produce one liter of solution
B)the breaking of a large rock into very many smaller pieces of crushed gravel
C)the thawing of the frozen orange juice concentrate that was left in the car
D)the spontaneous chemical reaction of TNT (a solid chemical compound)wherein it decomposes into several simple compounds, some of which are gaseous
E)the absorption of odorous gaseous compounds by the charcoal filter in your home central air cleaning unit

Question 13

Which process is accompanied by an increase in the entropy of the system?

A)solid gold melting
B)the condensation of water on cold surface
C)the freezing of a popsicle
D)sewing a quilt
E)a cup of coffee cooling in a mug

Question 14

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

A)a cup of juice spreading across the floor after being spilled
B)soaking up a chemical spill with an absorbent material
C)the sublimation of iodine crystals
D)water boiling in a steam kettle
E)butter melting for a cake

Question 15

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

A)H₂O (s)
B)H₂O (l)
C)H₂O (g)

Question 16

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

A)CO₂ (s)
B)CO₂ (l)
C)CO₂ (g)

Question 17

Which statement below is always true for a spontaneous chemical reaction?

A) $\Delta$ S_sys + $\Delta$ S_surr = 0
B) $\Delta$ S_sys + $\Delta$ S_surr < 0
C) $\Delta$ S_sys + $\Delta$ S_surr > 0
D) $\Delta$ S_sys - $\Delta$ S_surr = 0
E) $\Delta$ S_sys - $\Delta$ S_surr < 0

Question 18

Of the species listed, which should possess the highest standard entropy (S°)for one mole of substance?

A)(CH₃)₂CO(l)
B)C₄H₁₀(g)
C)K₂SO₄(s)
D)H₂O(l)
E)Br₂(l)

Question 19

Which species has the highest standard entropy (S°)for one mole of substance?

A)Au(s)
B)Cd(s)
C)Hg(l)
D)Ni(s)
E)K(s)

Question 20

Which species has the greatest standard entropy (S°)for one mole of substance?

A)I₂(s)
B)Br₂(l)
C)N₂(l)
D)Cl₂(g)
E)He(l)

Question 21

Which species should possess the lowest standard entropy (S°)?

A)CH₄(g)
B)CO₂(s)
C)NH₃(l)
D)H₂O(l)
E)Ar(g)

Question 22

Which set has the species listed in order of increasing standard entropy, S°?

A)Au(s)< CaCO₃(s)< H₂O(l)
B)CaCO₃(s)< H₂O(l)< Au(s)
C)Au(s)< H₂O(l)< CaCO₃(s)
D)CaCO₃(s)< Au(s)< H₂O(l)

Question 23

Which set below has the species listed in order of increasing standard entropy, S°?

A)NaHCO₃(aq)< C₂H₅OH(l)< Cr(s)< N₂(g)
B)Cr(s)< N₂(g)< NaHCO₃(aq)< C₂H₅OH(l)
C)Cr(s)< C₂H₅OH(l)< NaHCO₃(aq)< N₂(g)
D)Cr(s)< NaHCO₃(aq)< C₂H₅OH(l)< N₂(g)
E)N₂(g)< NaHCO₃(aq)< Cr(s)< C₂H₅OH(l)

Question 24

Which set below has the species listed in order of increasing standard entropy, S°?

A)CaSO₄(s)< C₂H₅OH(l)< Ar(g)
B)CH₃CH₂-O-H(l)< Ar(g)< CaSO₄(s)
C)CaSO₄(s)< Ar(g)< C₂H₅OH(l)
D)C₂H₅OH(l)< CaSO₄(s)< Ar(g)

Question 25

For a certain chemical reaction, $\Delta$ H is < 0 and $\Delta$ S is < 0. This means that

A)we conclude the reaction must be spontaneous regardless of temperature and becomes even more so at higher temperatures.
B)we conclude the reaction must be spontaneous regardless of temperature and becomes even more so at lower temperatures.
C)we conclude the reaction may or may not be spontaneous, but spontaneity is favored by low temperatures.
D)we conclude the reaction may or may not be spontaneous, but spontaneity is favored by high temperatures.
E)we cannot make any conclusion about spontaneity or even tendencies from the limited information presented.

Question 26

For a certain chemical reaction, $\Delta$ H is > 0 and $\Delta$ S is < 0. This means that

A)we conclude the reaction must be nonspontaneous regardless of temperature.
B)we conclude the reaction must be spontaneous regardless of temperature and becomes even more so at lower temperatures.
C)we conclude the reaction may or may not be spontaneous, but spontaneity is favored by low temperatures.
D)we conclude the reaction may or may not be spontaneous, but spontaneity is favored by high temperatures.
E)we cannot make any conclusion about spontaneity or even tendencies from the limited information presented.

Question 27

The requirement for a spontaneous chemical reaction is

A) $\Delta$ G = 0.
B) $\Delta$ H > 0.
C) $\Delta$ S = 0.
D) $\Delta$ E > 0.
E) $\Delta$ G < 0.

Question 28

The normal melting point of benzoic acid is 122.4°C. Predict the signs of $\Delta$ H, $\Delta$ S, and ?G for the process in which liquid benzoic acid freezes at 120°C and 1 atm: C₇H₆O₂(l).C₇H₆O₂(s)

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

Question 29

The normal melting point of carbon dioxide is -78°C. Predict the signs of $\Delta$ H, $\Delta$ S, and $\Delta$ G for the process in which solid carbon dioxide sublimes at -50°C and 1 atm: CO₂(s).CO₂(g)

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

Question 30

The normal melting point of naphthalene is 80.3°C. Predict the signs of $\Delta$ H, $\Delta$ S, and $\Delta$ G for the process in which solid naphthalene melts at 82.5°C and 1 atm: C₁₀H₈(s). C₁₀H₈(l)

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

Question 31

Which property associated with a chemical reaction is dependent on how the reaction is carried out, not on just its initial and final states?

A) $\Delta$ S
B) $\Delta$ H
C) $\Delta$ E
D)w
E) $\Delta$ G

Question 32

A negative sign for $\Delta$ G indicates that, at constant temperature and pressure,

A)the reaction is spontaneous.
B) $\Delta$ S must be greater than zero.
C)the reaction must be exothermic.
D)the reaction must be fast.
E)the reaction must be endothermic.

Question 33

For the reaction 2NO(g)+ O₂(g) $\rarr$ 2NO₂(g), $\Delta$ H° = -113.1 kJ/mol and $\Delta$ S° = -145.3 J/K mol.Which of these statements is true?

A)The reaction is spontaneous at all temperatures.
B)The reaction is only spontaneous at low temperatures.
C)The reaction is only spontaneous at high temperatures.
D)The reaction is at equilibrium at 25°C under standard conditions.
E) $\Delta$ G° becomes more favorable as temperature increases.

Question 34

According to the second law of thermodynamics, a spontaneous reaction must result in

A)no change in free energy for the reaction.
B)the enthalpy of the universe increasing.
C)the entropy of the universe decreasing.
D)the temperature of the surrounding increasing.
E)the entropy of the universe increasing.

Question 35

Using the standard entropy values:
H₂(g), S° = +130.6 J mol^-1 K^-1
I₂(s), S° = +116.12 J mol^-1 K^-1
HI(g), S° = +206.0 J mol^-1 K^-1
Calculate the standard entropy change, S°, for the reaction:H₂(g)+ I₂(s) $\rarr$ 2 HI(g)

A)-40.8 J mol^-1 K^-1
B)+40.8 J mol^-1 K^-1
C)-165.3 J mol^-1 K^-1
D)+165.3 J mol^-1 K^-1
E)+206.0 J mol^-1 K^-1

Question 36

Using the standard entropy values:
NO(g), S° = +210.6 J mol^-1 K^-1
O₂(g), S° = +205.0 J mol^-1 K^-1
NO₂(g), S° = +240.5 J mol^-1 K^-1
Calculate the standard entropy change, S°, for the reaction:NO(g)+ ½ O₂(g) $\rarr$ NO₂(g)

A)-72.6 J mol^-1 K^-1
B)-175.1 J mol^-1 K^-1
C)+72.6 J mol^-1 K^-1
D)+175.1 J mol^-1 K^-1
E)-656.1 J mol^-1 K^-1

Question 37

Using the standard entropy values:
C₂H₄(g), S° = +219.8 J mol^-1 K^-
H₂(g), S° = +130.6 J mol^-1 K^-1
C₂H₆(g), S° = +229.5 J mol^-1 K^-1
Calculate the standard entropy change, S°, for the reaction:C₂H₄(g)+ H₂(g) $\rarr$ C₂H₆(g)

A)+120.9 J mol^-1 K^-1
B)-98.9 J mol^-1 K^-1
C)-120.9 J mol^-1 K^-1
D)+140.3 J mol^-1 K^-1
E)+579.9 J mol^-1 K^-1

Question 38

Using the standard entropy values:
SO₂(g), S° = +248.0 J mol^-1 K^-1
SO₃(g), S° = +256.0 J mol^-1 K^-1
NO(g), S° = +210.6 J mol^-1 K^-1
NO₂(g), S° = +240.5 J mol^-1 K^-1
Calculate the standard entropy change, $\Delta$ S°, for the reaction:NO₂(g)+ SO₂(g) $\rarr$ NO(g)+ SO₃(g)

A)-6.2 J mol^-1 K^-1
B)+21.9 J mol^-1 K^-1
C)-21.9 J mol^-1 K^-1
D)-37.9 J mol^-1 K^-1
E)+52.9 J mol^-1 K^-1

Question 39

Using the standard free energies of formation:
BaCO₃(s), $\Delta$ G°_f = -1139.0 kJ mol^-1
BaSO₄(s), $\Delta$ G°_f = -1353.0 kJ mol^-1
CO₂(g), $\Delta$ G°_f = -394.4 kJ mol^-1
SO₃(g), $\Delta$ G°_f = -370.0 kJ mol^-1
Calculate the standard free energy change, $\Delta$ G°, for the reaction:BaCO₃(s)+ SO₃(g) $\rarr$ BaSO₄(s)+ CO₂(g)

A)+189.6 kJ mol^-1
B)-238.4 kJ mol^-1
C)+472.4 kJ mol^-1
D)+238.4 kJ mol^-1
E)-2516.4 kJ mol^-1

Question 40

Using the standard free energies of formation:
NO₂(g), $\Delta$ G°_f = +51.84 kJ mol^-1
NO(g), $\Delta$ G°_f = +86.69 kJ mol^-1
SO₂(g), $\Delta$ G°_f = -300.0 kJ mol^-1
SO₃(g), $\Delta$ G°_f = -370.0 kJ mol^-1
Calculate the standard free energy change, $\Delta$ G°, for the reaction:NO₂(g)+ SO₂(g) $\rarr$ NO(g)+ SO₃(g)

A)-35.15 kJ mol^-1
B)-104.9 kJ mol^-1
C)-429.2 kJ mol^-1
D)-619.6 kJ mol^-1
E)+35.15 kJ mol^-1

Question 41

Given the data:
H₂(g), $\Delta$ H°_f = 0 kJ mol^-1, S° = +130.6 J mol^-1 K^-1
I₂(s), $\Delta$ H°_f = 0 kJ mol^-1, S° = +116.12 J mol^-1 K^-1
HI(g), $\Delta$ H°_f = +26 kJ mol^-1, S° = +206 J mol^-1 K^-1
Calculate the standard free energy change, $\Delta$ G°, for the reaction:H₂(g)+ I₂(s) $\rarr$ 2 HI(g)

A)+2.7 kJ mol^-1
B)-46.5 kJ mol^-1
C)-2.7 kJ mol^-
D)+128.2 kJ mol^-1
E)-165.3 kJ mol^-1

Question 42

Given the data:
Ag₂O(s), $\Delta$ H°_f = -31.1 kJ mol^-1, S° = +121.3 J mol^-1 K^-1
O₂(g), $\Delta$ H°_f = 0.00 kJ mol^-1, S° = +205 J mol^-1 K^-1
Ag(s), $\Delta$ H°_f = 0.00 kJ mol^-1, S° = +42.55 J mol^-1 K^-1
Calculate the standard free energy change $\Delta$ G°, for the reaction:Ag₂O(s) $\rarr$ 2 Ag(s)+ ½ O₂(g)

A)+11.3 kJ mol^-1
B)-24.0 kJ mol^-1
C)-38.2 kJ mol^-1
D)-50.4 kJ mol^-1
E)-1.3 kJ mol^-1

Question 43

Given the data:
N₂(g), $\Delta$ H°_f = 0.00 kJ mol^-1, S° = +191.5 J mol^-1 K^-1
H₂(g), $\Delta$ H°_f = 0.00 kJ mol^-1, S° = +130.6 J mol^-1 K^-1
NH₃(g), $\Delta$ H°_f = -46.0 kJ mol^-1, S° = +192.5 J mol^-1 K^-1
Calculate the standard free energy change, $\Delta$ G° for the reaction:N₂(g)+ 3 H₂(g) $\rarr$ 2 NH₃(g)

A)-7.4 kJ mol^-1
B)-32.9 kJ mol^-1
C)-84.6 kJ mol^-1
D)+112.3 kJ mol^-1
E)+32.9 kJ mol^-1

Question 44

Given the data:
NH₃(g), $\Delta$ H°_f = -46.0 kJ mol^-1, S° = +192.5 J mol^-1 K^-1
NO(g), $\Delta$ H°_f = +90.4 kJ mol^-1, S° = +210.6 J mol^-1 K^-1
H₂O(l), $\Delta$ H°_f = -286 kJ mol^-1, S° = +69.96 J mol^-1 K^-1
O₂(g), $\Delta$ H°_f = 0.00 kJ mol^-1, S° = +205 J mol^-1 K^-1
Calculate the standard free energy change, $\Delta$ G°, for the reaction:2 NH₃(g)+ 5/2 O₂(g) $\rarr$ 2 NO(g)+ 3 H₂O(l)

A)-100.8 kJ mol^-1
B)-206.7 kJ mol^-1
C)-276.5 kJ mol^-1
D)-505.8 kJ mol^-1
E)+664.3 kJ mol^-1

Question 45

Given the data:
PbO(s), $\Delta$ H°_f = -217.3 kJ mol^-1, S° = +68.7 J mol^-1 K^?1
PbO₂(s), $\Delta$ H°_f = -277.0 kJ mol^-1, S° = +68.6 J mol^-1K^-1
O₂(g), $\Delta$ H°_f = 0.00 kJ mol^-1, S° = +205 J mol^-1 K^-1
Calculate the standard free energy change, ?G°, for the reaction:PbO(s)+ ½ O₂(g) PbO₂(s)

A)+1.45 kJ mol^-1
B)-29.1 kJ mol^-1
C)-68.3 kJ mol^-1
D)-90.3 kJ mol^-1
E)+29.1 kJ mol^-1

Question 46

Using the data:
C₂H₄(g), $\Delta$ H°_f = +51.9 kJ mol^-1, S° = 219.8 J mol^-1 K^-1
CO₂(g), $\Delta$ H°_f = -394 kJ mol^-1, S° = 213.6 J mol⁺¹ K^-1
H₂O(l), $\Delta$ H°_f = -286.0 kJ mol^-1, S° = 69.96 J mol^-1 K^-1
O₂(g), $\Delta$ H°_f = 0.00 kJ mol^-1, S° = 205 J mol^-1 K^-1
Calculate the maximum amount of work that can be obtained, at 25.0 °C, from the process:C₂H₄(g)+ 3 O₂(g) $\rarr$ 2 CO₂(g)+ 2 H₂O(l)

A)1332 kJ mol^-1
B)1380 kJ mol^-1
C)1451 kJ mol^-1
D)1492 kJ mol^-1
E)2422 kJ mol^-1

Question 47

Which of the following is the best example of a thermodynamically reversible process?

A)water dripping out of a leak in a pail
B)the conversion of ice to water at 0°C
C)the popping of a balloon
D)the dissolving of sugar into water
E)the cracking of a block of ice with a hammer

Question 48

Which of the following is the best example of a thermodynamically reversible process?

A)a nail rusting in a deck
B)the dispersion of food coloring when added to a glass of water
C)the buring of a piece of paper
D)the conversion of water to ice in a sealed at 0°C
E)the conversion of dry ice to CO₂ gas on a counter at room temperature

Question 49

In order to get the most efficient work out of a thermochemical process, what needs to be done?

A)The process must take place at high temperature.
B)The process must be endothermic.
C)The process must be exothermic.
D)The process must be done reversibly.
E)The process must cause an increase in entropy for the system.

Question 50

Using the data:
C₂H₆(g), $\Delta$ H°_f = -84.5 kJ mol^-1, S° = +229.5 J mol^-1 K^-1
CO₂(g), $\Delta$ H°_f = -394.0 kJ mol^-1, S° = +213.6 J mol^-1 K^-1
H₂O(l), $\Delta$ H°_f = -286.0 kJ mol^-1, S° = +69.96 J mol^-1 K^-1
O₂(g), $\Delta$ H°_f = 0.00 kJ mol^-1, S° = +205 J mol^-1 K^-1
Calculate the maximum amount of work that can be obtained, at 25.0 °C, from the process:C₂H₆(g)+ 7 O₂(g) $\rarr$ 4 CO₂(g)+ 6 H₂O(l), per mole of C₂H₆

A)1426 kJ mol^-1
B)1469 kJ mol^-1
C)1654 kJ mol^-1
D)2938 kJ mol^-1
E)3029 kJ mol^-1

Question 51

Assuming that, since the physical states do not change, the values of ?H and sS do not change as we raise the temperature in the reaction below. Using the following values at 298 K,
CdO(s), $\Delta$ H°_f = -258.2 kJ mol^-1, S° = +54.8 J mol^-1 K^-1
CdSO₄(s), $\Delta$ H°_f = -933.5 kJ mol^-1, S° = +123 J mol^-1 K^?1
SO₃(g), $\Delta$ H°_f = -396 kJ mol^-1, S° = +256 J mol^-1 K^-1
Calculate a value for the free energy change, $\Delta$ G°_T for the reaction,CdSO₄(s) $\rarr$ CdO(s)+ SO₃(g)at 750 K

A)+223.3 kJ mol^-1
B)+138.5 kJ mol^-1
C)-140.6 kJ mol^-1
D)+420.5 kJ mol^-1
E)-420.5 kJ mol^-1

Question 52

Assuming that, since the physical states do not change, the values of $\Delta$ H and $\Delta$ S do not change as we raise the temperature in the reaction below. Using the following values at 25 °C,
CaO(s), $\Delta$ H°_f = -635.5 kJ mol^-1, S° = +40.0 J mol^-1 K^-1
CaCO₃(s), $\Delta$ H°_f = -1207 kJ mol^-1, S° = +92.9 J mol^-1 K^-1
CO₂(g), $\Delta$ H°_f = -394 kJ mol^-1, S° = +213.6 J mol^-1 K^-1
Calculate a value for the free energy change, $\Delta$ G°_T for the reaction,CaCO_3(s) $\rarr$ CaO(s)+ CO₂(g)at 815 °C

A)+2.6 kJ mol^-1
B)+46.5 kJ mol^-1
C)-174.7 kJ mol^-1
D)+308.5 kJ mol^-1
E)-352.4 kJ mol^-1

Question 53

Naphthalene (C₁₀H₈)is a solid at room temperature. It sublimes by the following process. Using the data below determine the best estimate of the sublimation temperature for naphthalene (the temperature at which this reaction will become spontaneous under standard state conditions.
C₁₀H₈(s) $\rarr$ C₁₀H₈(g)
$\Delta$ H° = 72.1 kJ/mol
$\Delta$ S° = 196.55 J/K mol

A)2.73 K
B)421 K
C)561 K
D)367 K
E)315 K

Question 54

Assuming that, since the physical states do not change, the values of $\Delta$ H and $\Delta$ S do not change as we raise the temperature, and using,
N₂(g), $\Delta$ H°_f = 0.00 kJ mol^-1, S° = +191.5 J mol^-1 K^-1
H₂(g), $\Delta$ H°_f = 0.00 kJ mol^-1, S° = +130.6 J mol^-1 K^-1
NH₃(g), $\Delta$ H°_f = -46.0 kJ mol^-1, S° = +192.5 J mol^-1 K^-1
Calculate a value for the free energy change, $\Delta$ G°_T for the reaction below, at 500 °C N₂(g)+ 3 H₂(g) $\rarr$ 2 NH₃(g)

A)+7.2 kJ mol^-1
B)+245.3 kJ mol^-1
C)+99.1 kJ mol^-1
D)+61.3 kJ mol^-1
E)+153.2 kJ mol^-1

Question 55

Over a wide temperature range, the reaction, M₂O₃(s)+ C(s) $\rarr$ M(s)+ CO₂(g), is spontaneous at low temperatures but non-spontaneous at high temperatures. If we assume that, since the physical states do not change, the values of $\Delta$ G°_T and $\Delta$ S°_T are constant over this temperature range, we can then deduce that

A) $\Delta$ H < 0 and $\Delta$ S > 0.
B) $\Delta$ H < 0 and $\Delta$ S < 0.
C) $\Delta$ H > 0 and $\Delta$ S < 0.
D) $\Delta$ H > 0 and $\Delta$ S > 0.
E)The information is insufficient to make any judgment as to the signs of $\Delta$ H and $\Delta$ S.

Question 56

Given the data:
Ag₂O(s), $\Delta$ H°_f = -31.1 kJ mol^-1, S° = +121.3 J mol^-1 K^-1
Ag(s), $\Delta$ H°_f = 0.00 kJ mol^-1, S° = +42.55 J mol^-1 K^-1
O₂(g), $\Delta$ H°_f = 0.00 kJ mol^-1, S° = +205.0 J mol^-1 K^-1
Calculate the temperature at which $\Delta$ G°_T = 0 for the reaction, Ag₂O(s) $\rarr$ 2 Ag(s)+ ½ O₂(g). Assume that, since the physical states do not change, $\Delta$ H° and $\Delta$ S° are independent of temperature between -50.0 °C and 950.0 °C.

A)+196 °C
B)+246 °C
C)+423 °C
D)+610 °C
E)+818 °C

Question 57

The thermochemical equation representing one process used for the synthesis of ammonia involves the equilibrium shown,N₂(g)+ 3 H₂(g) 2 NH₃(g)or this reaction, ?H° = -92.2 kJ, $\Delta$ G° = -33.4 kJ. All things considered, one concludes that

A)the coefficients give us the mole ratios but not the volume ratios of the reacting species.
B)an increase in pressure favors an increase in the yield of ammonia.
C)carrying out the reaction at a higher temperature shifts the position of equilibrium to the right, thus favoring an increase in the yield of ammonia.
D)cooling the mixture to remove ammonia from the reaction mixture unfortunately also decreases the overall yield of ammonia.
E)the mixture does not need heating, in fact, cooling the mixture assists the rapid establishment of equilibrium.

Question 58

Determine the equilibrium constant K_p at 25°C for the reaction:N₂(g)+ 3H₂(g) 2NH₃(g)( $\Delta$ G°_f (NH₃(g))= -16.6 kJ/mol)

A)1.52 × 10^-6
B)2.60
C)8.28 × 10^-2
D)13.4
E)6.60 × 10⁵

Question 59

Determine the equilibrium constant K_p at 25°C for the reaction:2NO(g)+ O₂(g) 2NO₂(g)( $\Delta$ G°_rxn = -69.7 kJ/mol)

A)1.65 × 10¹²
B)8.28 × 10^-2
C)2.60
D)13.4
E)6.07 × 10^-13

Question 60

The equilibrium constant at 427°C for the reactionN₂(g)+ 3H₂(g) 2NH₃(g)is K_p = 9.4 × 10^-5. Calculate the value of $\Delta$ G° for the reaction at this temperature.

A)56 kJ/mol
B)-56 kJ/mol
C)-33 kJ/mol
D)33 kJ/mol
E)1.3 J/mol

Question 61

The equilibrium constant at 25°C for the reaction 2NO(g)+ O₂(g) 2NO₂(g)is K_p = 1.65 × 10¹². Calculate the value of $\Delta$ G° for the reaction at this temperature.

A)-4.09 kJ/mol
B)-5.85 kJ/mol
C)+5.85 kJ/mol
D)-69.7 kJ/mol
E)1.65 kJ/mol

Question 62

Using these bond energies, ?H°: Calculate the value of $\Delta$ H° of reaction for H₂C.H₂(g)+ H₂(g) $\rarr$ CH₃-CH₃(g)

A)-560 kJ/mol
B)-124 kJ/mol
C)-388 kJ/mol
D)+224 kJ/mol
E)-212 kJ/mol

Question 63

Using these bond energies, ?H°: Calculate the value of $\Delta$ H° of reaction for O.C.O(g)+ 3 H₂(g). CH₃-O-H(g)+ H-O-H(g)

A)-191 kJ/mol
B)+272 kJ/mol
C)-272 kJ/mol
D)-5779 kJ/mol
E)+5779 kJ/mol

Question 64

Using these bond energies, $\Delta$ H°: Calculate the value of $\Delta$ H° of reaction for H₂C.CH₂(g)+ H-O-H(g) $\rarr$ CH₃-CH₂-O-H(g)

A)-13 kJ/mol
B)-45 kJ/mol
C)-124 kJ/mol
D)+224 kJ/mol
E)-508 kJ/mol

Question 65

According to the first law of thermodynamics the internal energy of an isolated system must ________.

Question 66

According to the first law of thermodynamics if the energy of a system decreases ________ amount of energy must be transferred to the surroundings.

Question 67

The ________ phase of a substance will always have more entropy then the liquid phase.

Question 68

The reaction N₂(g)+ 3H₂(g)→ 2NH₃(g)would result in a(n)________ in entropy of the system.

Question 69

Consider the following chemical reaction: Cr³⁺(aq)+ 6H₂O(l)→ [Cr(H₂O)₆]³⁺(aq)Would this reaction have a positive or negative entropy of formation?

Question 70

Which of the following processes are accompanied by an increase in entropy. One or more of the following answers may be selected.
1. 2SO₂(g)+ O₂(g)→ 2SO₃(g)
2. H₂O(l)→ H₂O(s)
3. Br₂(l)→ Br₂(g)
4. H₂O₂(l)→ H₂O(l)+ (1/2)O₂(g)

Question 71

According to the second law of thermodynamics, the entropy of the universe is always ________.

Question 72

For the reaction H₂(g)+ S(s)→ H₂S(g), ΔH° = -20.2 kJ/mol and ΔS° = +43.1 J/K·mol, at which temperatures would the reaction be spontaneous?

Question 73

For the reaction 2NO(g)+ O₂(g)→ 2NO₂(g), ΔH° = −113.1 kJ/mol and ΔS° = -145.3 J/K·mol. Under which temperature conditions would the reaction be spontaneous?

Question 74

Consider a reaction that is both exothermic and increases entropy. How will temperature affect the spontaneity of the process?

Question 75

Consider a reaction that is both endothermic and increases entropy. How will temperature affect the spontaneity of the process?

Question 76

Consider a reaction that is both exothermic and decreases order. How will temperature affect the spontaneity of the process?

Question 77

Consider a reaction that is both endothermic and increasingly ordered. How will temperature affect the spontaneity of the process?

Question 78

Describe, using the free energy relationship ΔG = ΔH - TΔS, the process of a hot object coming into thermal equilibrium with a cold object.

Question 79

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

Question 80

The entropy of perfectly ordered pure crystalline substance at zero Kelvin is ________.