Question 1

For a chemical reaction to be spontaneous only at low temperatures,which of the following conditions must be met?

Accepted Answer

A) ($\Delta$S°·> 0,$\Delta$H° > 0) 
B) ($\Delta$S° > 0,$\Delta$H°  0) 
E) ($\Delta$G° > 0) 
A) ($\Delta$S°·> 0,$\Delta$H° > 0) 
B) ($\Delta$S° > 0,$\Delta$H°  0) 
E) ($\Delta$G° > 0)

Question 2

A chemical reaction has $\Delta$H° = 42.8 kJ and $\Delta$S° = 92.5 J/K,at 25°C.Calculate the temperature at which $\Delta$G° = 0.State any approximation involved in your calculation.

Accepted Answer

T = 463 K.The calculation is b

Question 3

Calculate $\Delta$G° for the combustion of propane.
C3H8(g)+ 5O2(g) $\to$3CO2(g)+ 4H2O(g)

Accepted Answer

A) -2073.1 kJ 
B) -1387.3 kJ 
C) -598.5 kJ 
D) 598.5 kJ 
E) 2073.1 kJ 
A) -2073.1 kJ 
B) -1387.3 kJ 
C) -598.5 kJ 
D) 598.5 kJ 
E) 2073.1 kJ

Question 4

State the second and third laws of thermodynamics.

Accepted Answer

All spontaneous processes are

Question 5

For a chemical reaction to be spontaneous only at high temperatures,which of the following conditions must be met?

Accepted Answer

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

Question 6

Which of the following values is based on the Third Law of Thermodynamics?

Accepted Answer

A) ($\Delta$H° f = 0 for Al(s)at 298 K) 
B) ($\Delta$G° f = 0 for H2(g)at 298 K) 
C) S° = 51.446 J/(mol·K)for Na(s)at 298 K 
D) q sys 2O(l) $\to$ H2O(s)at 0°C 
E) None of these choices is correct. 
A) ($\Delta$H° f = 0 for Al(s)at 298 K) 
B) ($\Delta$G° f = 0 for H2(g)at 298 K) 
C) S° = 51.446 J/(mol·K)for Na(s)at 298 K 
D) q sys 2O(l) $\to$ H2O(s)at 0°C 
E) None of these choices is correct.

Question 7

Which of the following is true for pure oxygen gas,O2(g)at 25°C?

Accepted Answer

A) ($\Delta$H° f > 0) 
B) ($\Delta$H° f f > 0) 
D) ($\Delta$G° f  0) 
A) ($\Delta$H° f > 0) 
B) ($\Delta$H° f f > 0) 
D) ($\Delta$G° f  0)

Question 8

When a sky diver free-falls through the air,the process is

Accepted Answer

A) non-spontaneous because he is accelerating due to the force applied by gravity. 
B) non-spontaneous because he is losing potential energy. 
C) non-spontaneous because he had planned the jump for two weeks. 
D) spontaneous. 
E) in equilibrium. 
A) non-spontaneous because he is accelerating due to the force applied by gravity. 
B) non-spontaneous because he is losing potential energy. 
C) non-spontaneous because he had planned the jump for two weeks. 
D) spontaneous. 
E) in equilibrium.

Question 9

Consider the figure below which shows $\Delta$G° for a chemical process plotted against absolute temperature.From this plot,it is reasonable to conclude that:

Accepted Answer

A) ($\Delta$H° > 0,$\Delta$S° > 0) B) ($\Delta$H° > 0,$\Delta$S° 0) D) ($\Delta$H° < 0,$\Delta$S° < 0) E) None of these choices is correct. A) ($\Delta$H° > 0,$\Delta$S° > 0) B) ($\Delta$H° > 0,$\Delta$S° 0) D) ($\Delta$H° < 0,$\Delta$S° < 0) E) None of these choices is correct.

Question 10

The temperature at which the following process reaches equilibrium at 1.0 atm is the normal melting point for phosphoric acid.
H3PO4(s)  
H3PO4(l)
Use the following thermodynamic data at 298 K to determine this temperature.

Accepted Answer

A) 286 K 
B) 305 K 
C) 315 K 
D) 347 K 
E) 3170 K 
A) 286 K 
B) 305 K 
C) 315 K 
D) 347 K 
E) 3170 K

Question 11

Use the given data at 298 K to calculate $\Delta$G° for the reaction
2Cl2(g)+ SO2(g) $\to$ SOCl2(g)+ Cl2O(g)

Accepted Answer

A) 129.3 kJ 
B) 133.6 kJ 
C) 196.0 kJ 
D) 199.8 kJ 
E) 229.6 kJ 
A) 129.3 kJ 
B) 133.6 kJ 
C) 196.0 kJ 
D) 199.8 kJ 
E) 229.6 kJ

Question 12

Nitric oxide reacts with chlorine to form NOCl.The data refer to 298 K.
2NO(g)+ Cl2(g) $\to$ 2NOCl(g)
 
What is the value of $\Delta$G° for this reaction at 550 K?

Accepted Answer

A) -143.76 kJ 
B) -78.78 kJ 
C) -22.24 kJ 
D) -10.56 kJ 
E) 66,600 kJ 
A) -143.76 kJ 
B) -78.78 kJ 
C) -22.24 kJ 
D) -10.56 kJ 
E) 66,600 kJ

Question 13

In some spontaneous processes,the entropy of the surroundings decreases.

Accepted Answer

A) True 
 B)False

Question 14

For a given reaction,a change in the pressure may result in a change in the sign of $\Delta$G.

Accepted Answer

A) True 
 B)False

Question 15

Hydrogen sulfide decomposes according to the following reaction
2H2S(g) $\to$2H2(g)+ S2(g)
For this reaction at 298K $\Delta$S° = 78.1 J/K,$\Delta$H° = 169.4 kJ,and $\Delta$G° = 146.1 kJ.What is the value of $\Delta$G° at 900 K?

Accepted Answer

A) -69,881 kJ 
B) 48.4 kJ 
C) 99.1 kJ 
D) 240 kJ 
E) 441 kJ 
A) -69,881 kJ 
B) 48.4 kJ 
C) 99.1 kJ 
D) 240 kJ 
E) 441 kJ

Question 16

Which of the following results in a decrease in the entropy of the system?

Accepted Answer

A) O2(g),300 K $\to$ O2(g),400 K 
B) H2O(s),0°C $\to$  H2O(l),0°C 
C) N2(g),25°C $\to$  N2(aq),25°C 
D) NH3(l),-34.5°C $\to$  NH3(g),-34.5°C 
E) 2H2O2(g) $\to$  2H2O(g)+ O2(g) 
A) O2(g),300 K $\to$ O2(g),400 K 
B) H2O(s),0°C $\to$  H2O(l),0°C 
C) N2(g),25°C $\to$  N2(aq),25°C 
D) NH3(l),-34.5°C $\to$  NH3(g),-34.5°C 
E) 2H2O2(g) $\to$  2H2O(g)+ O2(g)

Question 17

For what signs of $\Delta$H and $\Delta$S will a process
a.be spontaneous at high temperatures but not at low temperatures?
b.not be spontaneous at any temperatures?

Accepted Answer

a.@#LAT-DLM&H > 0,@#LAT-DLM&S

Question 18

a.Explain what is meant by a spontaneous process.
b.Is a spontaneous process necessarily a rapid one? Explain,and provide a real reaction as an example to illustrate your answer.

Accepted Answer

a.A spontaneous process is one which wil

Question 19

For the reaction of xenon and fluorine gases to form solid XeF4,$\Delta$H° = -251 kJ and $\Delta$G° = -121 kJ at 25°C.Calculate $\Delta$S° for the reaction.

Accepted Answer

The answer of For the reaction of xenon and fluorine...

Question 20

You are given pure samples of ammonia,NH3(g),and nitrogen trifluoride,NF3(g).What prediction would you make concerning their standard molar entropies at 298 K?

Accepted Answer

A) S°ammonia > S°nitrogen trifluoride 
B) S°ammonia nitrogen trifluoride 
C) S°ammonia $\approx$ S°nitrogen trifluoride 
D) Other conditions need to be specified before a reliable prediction can be made. 
E) Even if more conditions are specified,a reliable prediction cannot be made. 
A) S°ammonia > S°nitrogen trifluoride 
B) S°ammonia nitrogen trifluoride 
C) S°ammonia $\approx$ S°nitrogen trifluoride 
D) Other conditions need to be specified before a reliable prediction can be made. 
E) Even if more conditions are specified,a reliable prediction cannot be made.

Exam 20: Thermodynamics: Entropy, free Energy, and the Direction of Chemical Reactions

For a chemical reaction to be spontaneous only at low temperatures,which of the following conditions must be met?

A chemical reaction has Δ\DeltaΔ H° = 42.8 kJ and Δ\DeltaΔ S° = 92.5 J/K,at 25°C.Calculate the temperature at which Δ\DeltaΔ G° = 0.State any approximation involved in your calculation.

Calculate Δ\DeltaΔ G° for the combustion of propane. C3H8(g)+ 5O2(g) →\to→ 3CO2(g)+ 4H2O(g)

State the second and third laws of thermodynamics.

For a chemical reaction to be spontaneous only at high temperatures,which of the following conditions must be met?

Which of the following values is based on the Third Law of Thermodynamics?

Which of the following is true for pure oxygen gas,O2(g)at 25°C?

When a sky diver free-falls through the air,the process is

Consider the figure below which shows Δ\DeltaΔ G° for a chemical process plotted against absolute temperature.From this plot,it is reasonable to conclude that:

The temperature at which the following process reaches equilibrium at 1.0 atm is the normal melting point for phosphoric acid. H3PO4(s) H3PO4(l) Use the following thermodynamic data at 298 K to determine this temperature.

Use the given data at 298 K to calculate Δ\DeltaΔ G° for the reaction 2Cl2(g)+ SO2(g) →\to→ SOCl2(g)+ Cl2O(g)

Nitric oxide reacts with chlorine to form NOCl.The data refer to 298 K. 2NO(g)+ Cl2(g) →\to→ 2NOCl(g) What is the value of Δ\DeltaΔ G° for this reaction at 550 K?

In some spontaneous processes,the entropy of the surroundings decreases.

For a given reaction,a change in the pressure may result in a change in the sign of Δ\DeltaΔ G.

Hydrogen sulfide decomposes according to the following reaction 2H2S(g) →\to→ 2H2(g)+ S2(g) For this reaction at 298K Δ\DeltaΔ S° = 78.1 J/K, Δ\DeltaΔ H° = 169.4 kJ,and Δ\DeltaΔ G° = 146.1 kJ.What is the value of Δ\DeltaΔ G° at 900 K?

Which of the following results in a decrease in the entropy of the system?

For what signs of Δ\DeltaΔ H and Δ\DeltaΔ S will a process a.be spontaneous at high temperatures but not at low temperatures? b.not be spontaneous at any temperatures?

a.Explain what is meant by a spontaneous process. b.Is a spontaneous process necessarily a rapid one? Explain,and provide a real reaction as an example to illustrate your answer.

For the reaction of xenon and fluorine gases to form solid XeF4, Δ\DeltaΔ H° = -251 kJ and Δ\DeltaΔ G° = -121 kJ at 25°C.Calculate Δ\DeltaΔ S° for the reaction.

You are given pure samples of ammonia,NH3(g),and nitrogen trifluoride,NF3(g).What prediction would you make concerning their standard molar entropies at 298 K?

Keys to the Study of Chemistry

The Components of Matter

Stoichiometry of Formulas and Equations

Three Major Classes of Chemical Reactions

Gases and the Kinetic-Molecular Theory

Thermochemistry: Energy Flow and Chemical Change

Quantum Theory and Atomic Structure

Electron Configuration and Chemical Periodicity

Models of Chemical Bonding

The Shapes of Molecules

Theories of Covalent Bonding

Intermolecular Forces: Liquids,solids,and Phase Changes

The Properties of Solutions

The Main-Group Elements: Applying Principles of Bonding and Structure

Organic Compounds and the Atomic Properties of Carbon

Kinetics: Rates and Mechanisms of Chemical Reactions

Equilibrium: the Extent of Chemical Reactions

Acid-Base Equilibria

Ionic Equilibria in Aqueous Systems

Electrochemistry: Chemical Change and Electrical Work

The Transition Elements and Their Coordination Compounds

Nuclear Reactions and Their Applications

Filters

A chemical reaction has $\Delta$ H° = 42.8 kJ and $\Delta$ S° = 92.5 J/K,at 25°C.Calculate the temperature at which $\Delta$ G° = 0.State any approximation involved in your calculation.

Calculate $\Delta$ G° for the combustion of propane. C₃H₈(g)+ 5O₂(g) $\to$ 3CO₂(g)+ 4H₂O(g) $Calculate \Delta G° for the combustion of propane. C<sub>3</sub>H<sub>8</sub>(g)+ 5O<sub>2</sub>(g) \to 3CO<sub>2</sub>(g)+ 4H<sub>2</sub>O(g)$

Which of the following is true for pure oxygen gas,O₂(g)at 25°C?

The temperature at which the following process reaches equilibrium at 1.0 atm is the normal melting point for phosphoric acid. H₃PO₄(s) H₃PO₄(l) Use the following thermodynamic data at 298 K to determine this temperature.

Use the given data at 298 K to calculate $\Delta$ G° for the reaction 2Cl₂(g)+ SO₂(g) $\to$ SOCl₂(g)+ Cl₂O(g) $Use the given data at 298 K to calculate \Delta G° for the reaction 2Cl<sub>2</sub>(g)+ SO<sub>2</sub>(g) \to SOCl<sub>2</sub>(g)+ Cl<sub>2</sub>O(g)$

For a given reaction,a change in the pressure may result in a change in the sign of $\Delta$ G.

Hydrogen sulfide decomposes according to the following reaction 2H₂S(g) $\to$ 2H₂(g)+ S₂(g) For this reaction at 298K $\Delta$ S° = 78.1 J/K, $\Delta$ H° = 169.4 kJ,and $\Delta$ G° = 146.1 kJ.What is the value of $\Delta$ G° at 900 K?

For what signs of $\Delta$ H and $\Delta$ S will a process a.be spontaneous at high temperatures but not at low temperatures? b.not be spontaneous at any temperatures?

For the reaction of xenon and fluorine gases to form solid XeF₄, $\Delta$ H° = -251 kJ and $\Delta$ G° = -121 kJ at 25°C.Calculate $\Delta$ S° for the reaction.

You are given pure samples of ammonia,NH₃(g),and nitrogen trifluoride,NF₃(g).What prediction would you make concerning their standard molar entropies at 298 K?