Question 1

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

Accepted Answer

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 
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 2

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

Accepted Answer

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

Question 3

Choose the INCORRECT statement.

Accepted Answer

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 Keq. 
E) ?rG ° = ?rH° - T?rS°. 
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 Keq. 
E) ?rG ° = ?rH° - T?rS°.

Question 4

For the reaction I2(s)+ Cl2(g)→ 2 ICl(g),ΔrH° = 36 kJ and ΔrS° = 158.8 J/K at 25 °C.Calculate ΔrG° for the process at 25 °C.

Accepted Answer

A) -11.3 kJ 
B) -4730 kJ 
C) -393 kJ 
D) 32 kJ 
E) 83.3 kJ 
A) -11.3 kJ 
B) -4730 kJ 
C) -393 kJ 
D) 32 kJ 
E) 83.3 kJ

Question 5

The enthalpy change for converting 10.0 g of ice at -25.0 °C to water at 80.0 °C is ________ kJ.The specific heats of ice,water,and steam are     And   Respectively.For   O,   = 6.01 kJ mol-1,and  .

Accepted Answer

A) 12.28 
B) 6.16 
C) 3870 
D) 7.21 
E) 9.88 
A) 12.28 
B) 6.16 
C) 3870 
D) 7.21 
E) 9.88

Question 6

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

Accepted Answer

A) True 
 B)False

Question 7

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

Accepted Answer

A) True 
 B)False

Question 8

Choose the INCORRECT statement.

Accepted Answer

A) The van't Hoff equation is ln   
B) Keq 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 Keq 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. 
A) The van't Hoff equation is ln   
B) Keq 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 Keq 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 9

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

Accepted Answer

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 
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 10

For Cl2O(g)+ 3/2 O2(g)→ 2 ClO2 ,ΔrH° = 126 kJ/mol,and ΔrS° = -74.9 J/mol K at 377 °C.What is ΔrG° in kJ/mol?

Accepted Answer

A) 77.8 
B) 51.4 
C) 98.3 
D) 175 
E) 129.2 
A) 77.8 
B) 51.4 
C) 98.3 
D) 175 
E) 129.2

Question 11

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.

Accepted Answer

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 
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 12

In the Haber process,ammonia is synthesized from nitrogen and hydrogen: 
  (g)+   (g)→   (g)
ΔrG ° at 298 K for this reaction is -33.3 kJ mol-1.The value of ΔrG at 298 K for a reaction mixture that consists of 1.9 atm   ,1.6 atm   ,and 0.65 atm   Is ________ kJ mol-1.

Accepted Answer

A) -1.8 
B) -3.86 ×   
C) -7.25 × 103 
D) -104.5 
E) -40.5 
A) -1.8 
B) -3.86 ×   
C) -7.25 × 103 
D) -104.5 
E) -40.5

Question 13

ΔG is positive for a spontaneous reaction.

Accepted Answer

A) True 
 B)False

Question 14

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

Accepted Answer

A) True 
 B)False

Question 15

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

Accepted Answer

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

Question 16

A spontaneous process:

Accepted Answer

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 
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 17

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

Accepted Answer

A) True 
 B)False

Question 18

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

Accepted Answer

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 
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 19

For the reaction,
 
What is ΔrS°?

Accepted Answer

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 
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 20

For the reaction PCl5 (g)⇌ PCl3 (g)+ Cl2 (g),Kc = 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:

Accepted Answer

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

Exam 13: Spontaneous Change: Entropy and Gibbs Energy

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

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

Choose the INCORRECT statement.

For the reaction I2(s)+ Cl2(g)→ 2 ICl(g),ΔrH° = 36 kJ and ΔrS° = 158.8 J/K at 25 °C.Calculate ΔrG° for the process at 25 °C.

The enthalpy change for converting 10.0 g of ice at -25.0 °C to water at 80.0 °C is ________ kJ.The specific heats of ice,water,and steam are And Respectively.For O, = 6.01 kJ mol-1,and .

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

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

Choose the INCORRECT statement.

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

For Cl2O(g)+ 3/2 O2(g)→ 2 ClO2 ,ΔrH° = 126 kJ/mol,and ΔrS° = -74.9 J/mol K at 377 °C.What is ΔrG° in kJ/mol?

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.

In the Haber process,ammonia is synthesized from nitrogen and hydrogen: (g)+ (g)→ (g) ΔrG ° at 298 K for this reaction is -33.3 kJ mol-1.The value of ΔrG at 298 K for a reaction mixture that consists of 1.9 atm ,1.6 atm ,and 0.65 atm Is ________ kJ mol-1.

ΔG is positive for a spontaneous reaction.

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

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

A spontaneous process:

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

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

For the reaction, What is ΔrS°?

For the reaction PCl5 (g)⇌ PCl3 (g)+ Cl2 (g),Kc = 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:

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Introduction to Reactions in Aqueous Solutions

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Electrons in Atoms

The Periodic Table and Some Atomic Properties

Chemical Bonding I: Basic Concepts

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

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°

For the reaction I₂(s)+ Cl₂(g)→ 2 ICl(g),Δ_rH° = 36 kJ and Δ_rS° = 158.8 J/K at 25 °C.Calculate Δ_rG° for the process at 25 °C.

The enthalpy change for converting 10.0 g of ice at -25.0 °C to water at 80.0 °C is ________ kJ.The specific heats of ice,water,and steam are And Respectively.For O, = 6.01 kJ mol^-1,and .

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

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

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

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^-5M,calculate ΔG.

In the Haber process,ammonia is synthesized from nitrogen and hydrogen: (g)+ (g)→ (g) Δ_rG ° at 298 K for this reaction is -33.3 kJ mol^-1.The value of Δ_rG at 298 K for a reaction mixture that consists of 1.9 atm ,1.6 atm ,and 0.65 atm Is ________ kJ mol^-1.

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

For the reaction, What is Δ_rS°?

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: