Question 1

Rubidium has a heat of vaporization of 69.0 kJ/mol at its boiling point (686°C).Calculate $\Delta$S for this process, Rb(l)$\rarr$ Rb(g), at 1 atm and 686°C.

Accepted Answer

The answer of Rubidium has a heat of vaporization of...

Question 2

Which of the following is expected to have zero entropy? I.N2(g)at 273 K
II.SiO2(s, amorphous)at 0 K
III.NaCl(s)perfectly ordered crystal at 25 K
IV.Na(s)perfectly ordered crystal at 0 K

Accepted Answer

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

Question 3

Using the thermodynamic data provided below, calculate the standard change in entropy when one mole of sodium nitrate is dissolved in water?   Will the solubility of sodium nitrate increase or decrease if the temperature of the system is increased?

Accepted Answer

90.4 J/K·mol; solubi

Question 4

Which response includes all the following processes that are accompanied by an increase in entropy? 1)2SO2(g)+ O2(g)$\rarr$ SO3(g)
2)H2O(l)$\rarr$H2O(s)
3)Br2(l)$\rarr$Br2(g)
4)H2O2(l)$\rarr$ H2O(l)+ 1/2O2(g)

Accepted Answer

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

Question 5

With respect to the system only, a reaction with $\Delta$H  0 is predicted to be:

Accepted Answer

A) Spontaneous at all temperatures 
B) Spontaneous at high temperatures only 
C) Spontaneous at low temperatures only 
D) Nonspontaneous at all temperatures 
A) Spontaneous at all temperatures 
B) Spontaneous at high temperatures only 
C) Spontaneous at low temperatures only 
D) Nonspontaneous at all temperatures

Question 6

Aluminum forms a layer of aluminum oxide when exposed to air which protects the bulk metal from further corrosion. 4Al(s)+ 3O2(g)$\rarr$ 2Al2O3(s)
Using the thermodynamic data provided below, calculate $\Delta$S° for this reaction.

Accepted Answer

A) 182.3 J/K·mol 
B) 131.5 J/K·mol 
C) -182.3 J/K·mol 
D) -626.2 J/K·mol 
E) -802.9 J/K·mol 
A) 182.3 J/K·mol 
B) 131.5 J/K·mol 
C) -182.3 J/K·mol 
D) -626.2 J/K·mol 
E) -802.9 J/K·mol

Question 7

For the reaction H2(g)+ S(s)$\rarr$ H2S(g), $\Delta$H° = -20.2 kJ/mol and $\Delta$S° = +43.1 J/K·mol.Which of these statements is true?

Accepted Answer

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

Question 8

The normal boiling point of acetic acid is 118.1°C.If a sample of the acetic acid is at 125.2°C, Predict the signs of $\Delta$H, $\Delta$S, and $\Delta$G for the boiling process at this temperature.

Accepted Answer

A) ($\Delta$H > 0, $\Delta$S > 0, $\Delta$G  0, $\Delta$S > 0, $\Delta$G > 0) 
C) ($\Delta$H > 0, $\Delta$S  0, $\Delta$G > 0) 
E) ($\Delta$H  0) 
A) ($\Delta$H > 0, $\Delta$S > 0, $\Delta$G  0, $\Delta$S > 0, $\Delta$G > 0) 
C) ($\Delta$H > 0, $\Delta$S  0, $\Delta$G > 0) 
E) ($\Delta$H  0)

Question 9

The normal melting point sulfur is 113 °C.If a sample of solid sulfur is at 95 °C, Predict the signs of $\Delta$H, $\Delta$S, and $\Delta$G for the melting process at this temperature.

Accepted Answer

A) ($\Delta$H > 0, $\Delta$S > 0, $\Delta$G  0, $\Delta$S > 0, $\Delta$G > 0) 
C) ($\Delta$H > 0, $\Delta$S  0, $\Delta$G > 0) 
E) ($\Delta$H  0) 
A) ($\Delta$H > 0, $\Delta$S > 0, $\Delta$G  0, $\Delta$S > 0, $\Delta$G > 0) 
C) ($\Delta$H > 0, $\Delta$S  0, $\Delta$G > 0) 
E) ($\Delta$H  0)

Question 10

The free energy of formation of nitric oxide, NO, at 1000 K (roughly the temperature in an automobile engine during ignition)is about 78 kJ/mol.Calculate the equilibrium constant Kp for the reaction N2(g)+ O2(g)    
2NO(g)at this temperature.

Accepted Answer

Question 11

Using the thermodynamic data provided below, calculate Ksp for ZnS(s)at 25°.

Accepted Answer

2.4 × 10^-24 (

Question 12

HI has a normal boiling point of -35.4°C, and its $\Delta$Hvap is 21.16 kJ/mol.Calculate the molar entropy of vaporization ($\Delta$Svap).

Accepted Answer

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 
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 13

The entropy change $\Delta$S° for the reaction NH4Cl(s)$\rarr$NH3(g)+ HCl(g)will be negative.

Accepted Answer

A) True 
 B)False

Question 14

Sulfur can be separated from lead in the mineral galena, PbS(s), by "roasting" the ore in the presence of oxygen as shown in the following reaction:
2PbS(s)+ 3O2(g)$\rarr$2PbO(s)+ 2SO2(g)
Determine$\Delta$G for the above reaction at 850°C.

Accepted Answer

Question 15

With respect to the system only, a reaction with $\Delta$H > 0 and $\Delta$S < 0 is predicted to be:

Accepted Answer

A) Spontaneous at all temperatures 
B) Spontaneous at high temperatures only 
C) Spontaneous at low temperatures only 
D) Nonspontaneous at all temperatures 
A) Spontaneous at all temperatures 
B) Spontaneous at high temperatures only 
C) Spontaneous at low temperatures only 
D) Nonspontaneous at all temperatures

Question 16

Consider the reaction CO(g)+ 2H2(g)    
CH3OH(l)at 25°C.
$\Delta$G°f (CO)= -137.3 kJ/mol
$\Delta$G°f (CH3OH)= -166.3 kJ/mol
$\Delta$H°f (CO)= -110.5 kJ/mol
$\Delta$H°f (CH3OH)= -238.7 kJ/mol
S°(CO)= 197.9 J/K·mol
S°(CH3OH)= 126.8 J/K·mol
Calculate S°(H2(g)).

Accepted Answer

Question 17

Which of these species would you expect to have the lowest standard entropy (S°)?

Accepted Answer

A) Br2(l) 
B) Cl2(g) 
C) F2(g) 
D) H2(g) 
E) I2(s) 
A) Br2(l) 
B) Cl2(g) 
C) F2(g) 
D) H2(g) 
E) I2(s)

Question 18

For the reaction 3H2(g)+ N2(g)    
2NH3(g), Kc = 9.0 at 350°C.In what direction does this reaction proceed at 350°C under standard state conditions?

Accepted Answer

Question 19

Which of the following is consistent with a reaction that proceeds spontaneously in the reverse direction (assume all variables are in terms of the forward direction only)?

Accepted Answer

A) ($\Delta$G > 0, Q  K) 
D) ($\Delta$G° > 0, Q = K) 
E) ($\Delta$G > 0, Q > K) 
A) ($\Delta$G > 0, Q  K) 
D) ($\Delta$G° > 0, Q = K) 
E) ($\Delta$G > 0, Q > K)

Question 20

Dissolving an ionic solid in water always results in an increase in entropy.

Accepted Answer

A) True 
 B)False

Exam 17: Entropy Free Energy and Equilibrium

Rubidium has a heat of vaporization of 69.0 kJ/mol at its boiling point (686°C).Calculate Δ\DeltaΔ S for this process, Rb(l) →\rarr→ Rb(g), at 1 atm and 686°C.

Which of the following is expected to have zero entropy? I.N2(g)at 273 K II.SiO2(s, amorphous)at 0 K III.NaCl(s)perfectly ordered crystal at 25 K IV.Na(s)perfectly ordered crystal at 0 K

Using the thermodynamic data provided below, calculate the standard change in entropy when one mole of sodium nitrate is dissolved in water? Will the solubility of sodium nitrate increase or decrease if the temperature of the system is increased?

Which response includes all the following processes that are accompanied by an increase in entropy? 1)2SO2(g)+ O2(g) →\rarr→ SO3(g) 2)H2O(l) →\rarr→ H2O(s) 3)Br2(l) →\rarr→ Br2(g) 4)H2O2(l) →\rarr→ H2O(l)+ 1/2O2(g)

With respect to the system only, a reaction with Δ\DeltaΔ H < 0 and Δ\DeltaΔ S > 0 is predicted to be:

Aluminum forms a layer of aluminum oxide when exposed to air which protects the bulk metal from further corrosion. 4Al(s)+ 3O2(g) →\rarr→ 2Al2O3(s) Using the thermodynamic data provided below, calculate Δ\DeltaΔ S° for this reaction.

For the reaction H2(g)+ S(s) →\rarr→ H2S(g), Δ\DeltaΔ H° = -20.2 kJ/mol and Δ\DeltaΔ S° = +43.1 J/K·mol.Which of these statements is true?

The normal boiling point of acetic acid is 118.1°C.If a sample of the acetic acid is at 125.2°C, Predict the signs of Δ\DeltaΔ H, Δ\DeltaΔ S, and Δ\DeltaΔ G for the boiling process at this temperature.

The normal melting point sulfur is 113 °C.If a sample of solid sulfur is at 95 °C, Predict the signs of Δ\DeltaΔ H, Δ\DeltaΔ S, and Δ\DeltaΔ G for the melting process at this temperature.

The free energy of formation of nitric oxide, NO, at 1000 K (roughly the temperature in an automobile engine during ignition)is about 78 kJ/mol.Calculate the equilibrium constant Kp for the reaction N2(g)+ O2(g) 2NO(g)at this temperature.

Using the thermodynamic data provided below, calculate Ksp for ZnS(s)at 25°.

HI has a normal boiling point of -35.4°C, and its Δ\DeltaΔ Hvap is 21.16 kJ/mol.Calculate the molar entropy of vaporization ( Δ\DeltaΔ Svap).

The entropy change Δ\DeltaΔ S° for the reaction NH4Cl(s) →\rarr→ NH3(g)+ HCl(g)will be negative.

Sulfur can be separated from lead in the mineral galena, PbS(s), by "roasting" the ore in the presence of oxygen as shown in the following reaction: 2PbS(s)+ 3O2(g) →\rarr→ 2PbO(s)+ 2SO2(g) Determine Δ\DeltaΔ G for the above reaction at 850°C.

With respect to the system only, a reaction with Δ\DeltaΔ H > 0 and Δ\DeltaΔ S < 0 is predicted to be:

Consider the reaction CO(g)+ 2H2(g) CH3OH(l)at 25°C. Δ\DeltaΔ G°f (CO)= -137.3 kJ/mol Δ\DeltaΔ G°f (CH3OH)= -166.3 kJ/mol Δ\DeltaΔ H°f (CO)= -110.5 kJ/mol Δ\DeltaΔ H°f (CH3OH)= -238.7 kJ/mol S°(CO)= 197.9 J/K·mol S°(CH3OH)= 126.8 J/K·mol Calculate S°(H2(g)).

Which of these species would you expect to have the lowest standard entropy (S°)?

For the reaction 3H2(g)+ N2(g) 2NH3(g), Kc = 9.0 at 350°C.In what direction does this reaction proceed at 350°C under standard state conditions?

Which of the following is consistent with a reaction that proceeds spontaneously in the reverse direction (assume all variables are in terms of the forward direction only)?

Dissolving an ionic solid in water always results in an increase in entropy.

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Rubidium has a heat of vaporization of 69.0 kJ/mol at its boiling point (686°C).Calculate $\Delta$ S for this process, Rb(l) $\rarr$ Rb(g), at 1 atm and 686°C.

Which of the following is expected to have zero entropy? I.N₂(g)at 273 K II.SiO₂(s, amorphous)at 0 K III.NaCl(s)perfectly ordered crystal at 25 K IV.Na(s)perfectly ordered crystal at 0 K

Which response includes all the following processes that are accompanied by an increase in entropy? 1)2SO₂(g)+ O₂(g) $\rarr$ SO₃(g) 2)H₂O(l) $\rarr$ H₂O(s) 3)Br₂(l) $\rarr$ Br₂(g) 4)H₂O₂(l) $\rarr$ H₂O(l)+ ¹/₂O₂(g)

With respect to the system only, a reaction with $\Delta$ H < 0 and $\Delta$ S > 0 is predicted to be:

For the reaction H₂(g)+ S(s) $\rarr$ H₂S(g), $\Delta$ H° = -20.2 kJ/mol and $\Delta$ S° = +43.1 J/K·mol.Which of these statements is true?

The normal boiling point of acetic acid is 118.1°C.If a sample of the acetic acid is at 125.2°C, Predict the signs of $\Delta$ H, $\Delta$ S, and $\Delta$ G for the boiling process at this temperature.

The normal melting point sulfur is 113 °C.If a sample of solid sulfur is at 95 °C, Predict the signs of $\Delta$ H, $\Delta$ S, and $\Delta$ G for the melting process at this temperature.

The free energy of formation of nitric oxide, NO, at 1000 K (roughly the temperature in an automobile engine during ignition)is about 78 kJ/mol.Calculate the equilibrium constant K_p for the reaction N₂(g)+ O₂(g) 2NO(g)at this temperature.

Using the thermodynamic data provided below, calculate K_sp for ZnS(s)at 25°.

HI has a normal boiling point of -35.4°C, and its $\Delta$ H_vap is 21.16 kJ/mol.Calculate the molar entropy of vaporization ( $\Delta$ S_vap).

The entropy change $\Delta$ S° for the reaction NH₄Cl(s) $\rarr$ NH₃(g)+ HCl(g)will be negative.

With respect to the system only, a reaction with $\Delta$ H > 0 and $\Delta$ S < 0 is predicted to be:

For the reaction 3H₂(g)+ N₂(g) 2NH₃(g), K_c = 9.0 at 350°C.In what direction does this reaction proceed at 350°C under standard state conditions?