Question 1

Which, if any, of the following processes is spontaneous under the specified conditions?

Accepted Answer

A)  H2O(l) $\rightarrow$ H2O(s) at 25$\degree$C 
B)  CO2(s) $\rightarrow$ CO2(g) at 0$\degree$C 
C)  2H2O(g) $\rightarrow$H2(g) + O2(g) 
D)  C(graphite) $\rightarrow$ C(diamond) at 25$\degree$C and 1 atm pressure 
E)  None of these choices is spontaneous. 
A)  H2O(l) $\rightarrow$ H2O(s) at 25$\degree$C 
B)  CO2(s) $\rightarrow$ CO2(g) at 0$\degree$C 
C)  2H2O(g) $\rightarrow$H2(g) + O2(g) 
D)  C(graphite) $\rightarrow$ C(diamond) at 25$\degree$C and 1 atm pressure 
E)  None of these choices is spontaneous. B

Question 2

In a spontaneous process, the entropy of the system always increases.

Accepted Answer

A) True 
 B)False  False

Question 3

Which relationship or statement best describes $\Delta$S$\degree$ for the following reaction? 2H2S(g) + 3O2(g) $\rightarrow$2H2O(g) + 2SO2(g)

Accepted Answer

A)  ($\Delta$S$\degree$$\approx$ 0) 
B)  ($\Delta$S$\degree$  0) 
D)  ($\Delta$S$\degree$= $\Delta$H$\degree$/T) 
E)  More information is needed to make a reasonable prediction. 
A)  ($\Delta$S$\degree$$\approx$ 0) 
B)  ($\Delta$S$\degree$  0) 
D)  ($\Delta$S$\degree$= $\Delta$H$\degree$/T) 
E)  More information is needed to make a reasonable prediction. B

Question 4

In tables of thermodynamic data provided in chemistry books, one finds $\Delta$H$\degree$ S1U1B1fS1U1B0, $\Delta$G$\degree$ S1U1B1fS1U1B0 and S$\degree$listed. Briefly, explain why the entropy data are supplied as S$\degree$, while the enthalpy and free energy data are in the form of $\Delta$H$\degree$ S1U1B1fS1U1B0 and $\Delta$G$\degree$ 1U1B1fS1U1B0, respectively.

Accepted Answer

The third law specifies the state of zer

Question 5

A reaction has $\Delta$G= 10.0 kJ and $\Delta$G$\degree$ = 15.0 kJ at a temperature of 50$\degree$C. Calculate the value of the reaction quotient Q under these conditions.

Accepted Answer

A)  0.16 
B)  9.1 * 10¯5 
C)  1.1 *104 
D)  6.4 
E)  6.0 * 10¯6 
A)  0.16 
B)  9.1 * 10¯5 
C)  1.1 *104 
D)  6.4 
E)  6.0 * 10¯6

Question 6

For any reaction, if $\Delta$G $\degree$ > 0, then K < 1.

Accepted Answer

A) True 
 B)False

Question 7

You are given pure samples of ethane, C2H6(g), and toluene, C7H8(l). What prediction would you make concerning their standard molar entropies at 298 K?

Accepted Answer

A)  S$\degree$ethane > S$\degree$toluene 
B)  S$\degree$ethane toluene 
C)  S$\degree$ethane $\approx$ (S$\degree$toluene) / 3 
D)  S$\degree$ethane $\approx$S$\degree$toluene 
E)  Since toluene is much more complex than ethane, but ethane is in the gas phase while toluene is a liquid, none of these predictions can be confidently made without further information or calculations. 
A)  S$\degree$ethane > S$\degree$toluene 
B)  S$\degree$ethane toluene 
C)  S$\degree$ethane $\approx$ (S$\degree$toluene) / 3 
D)  S$\degree$ethane $\approx$S$\degree$toluene 
E)  Since toluene is much more complex than ethane, but ethane is in the gas phase while toluene is a liquid, none of these predictions can be confidently made without further information or calculations.

Question 8

A reaction is proceeding towards equilibrium. At a certain stage, the concentrations of reactants and products are such that $\Delta$G  = $\Delta$G$\degree$ . What conclusion can reasonably be drawn about the reaction at this time?

Accepted Answer

A) K > Q B) K < Q C) K = Q D) K = 1 E) Q = 1 A) K > Q B) K < Q C) K = Q D) K = 1 E) Q = 1

Question 9

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

Accepted Answer

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

Question 10

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$\degree$ammonia > S$\degree$nitrogen trifluoride 
B)  S$\degree$ammonia nitrogen trifluoride 
C)  S$\degree$ammonia $\approx$ S$\degree$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$\degree$ammonia > S$\degree$nitrogen trifluoride 
B)  S$\degree$ammonia nitrogen trifluoride 
C)  S$\degree$ammonia $\approx$ S$\degree$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.

Question 11

What is the free energy change, $\Delta$G$\degree$ , for the equilibrium between hydrogen iodide, hydrogen, and iodine at 453$\degree$C?
 Kc = 0.020

Accepted Answer

A)  6.4 kJ 
B)  8.8 kJ 
C)  15 kJ 
D)  19 kJ 
E)  24 kJ 
A)  6.4 kJ 
B)  8.8 kJ 
C)  15 kJ 
D)  19 kJ 
E)  24 kJ

Question 12

Given: C2H2(g) $\rightarrow$ 2C(graphite) + H2(g), $\Delta$G$\degree$ = -209 kJ
A sample of gaseous C2H2 (acetylene, or ethyne) was stored for one year, yet at the end of this period, the sample remained unchanged and no graphite or hydrogen gas had been formed. Briefly explain why there is no inconsistency between the sign of $\Delta$G$\degree$ and the apparent stability of the sample.

Accepted Answer

Relative to graphite and hydrogen, acety

Question 13

Which relationship or statement best describes $\Delta$S$\degree$ for the following reaction?
 Pb(s) + Cl2(g) $\rightarrow$ PbCl2(s)

Accepted Answer

A)  ($\Delta$S$\degree$ $\approx$ 0) 
B) ( $\Delta$S$\degree$  0) 
D) ( $\Delta$S$\degree$ = $\Delta$H$\degree$/T) 
E)  More information is needed to make a reasonable prediction. 
A)  ($\Delta$S$\degree$ $\approx$ 0) 
B) ( $\Delta$S$\degree$  0) 
D) ( $\Delta$S$\degree$ = $\Delta$H$\degree$/T) 
E)  More information is needed to make a reasonable prediction.

Question 14

Given: H2O(l) $\rightarrow$ H2O(s), $\Delta$H$\degree$ = -6.02 kJ at 273K, calculate the entropy change of the surroundings ($\Delta$Ssurr) when one mole of water freezes at 0$\degree$C and a pressure of one atmosphere.

Accepted Answer

A)  22.1 J/K 
B)  -22.1 J/K 
C)  397 J/K 
D)  -397 J/K 
E)  0.022 J/K 
A)  22.1 J/K 
B)  -22.1 J/K 
C)  397 J/K 
D)  -397 J/K 
E)  0.022 J/K

Question 15

The reaction of methane with water to form carbon dioxide and hydrogen is non-spontaneous at 298 K. At what temperature will this system make the transition from non-spontaneous to spontaneous? The data refer to 298 K.

Accepted Answer

A)  658 K 
B)  683 K 
C)  955 K 
D)  1047 K 
E)  1229 K 
A)  658 K 
B)  683 K 
C)  955 K 
D)  1047 K 
E)  1229 K

Question 16

Calculate$\Delta$S $\degree$for the reaction

Accepted Answer

A)  -254.96 J/K 
B)  -198.02 J/K 
C)  198.02 J/K 
D)  254.96 J/K 
E)  471.86 J/K 
A)  -254.96 J/K 
B)  -198.02 J/K 
C)  198.02 J/K 
D)  254.96 J/K 
E)  471.86 J/K

Question 17

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

Accepted Answer

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

Question 18

The free energy of a perfect crystal at absolute zero, is zero.

Accepted Answer

A) True 
 B)False

Question 19

Calculate $\Delta$G$\degree$for the combustion of propane.

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 20

A reaction has a positive value of $\Delta$H$\degree$  and a positive value of $\Delta$S$\degree$ . Draw a neat, labeled schematic plot to show how $\Delta$G$\degree$  (y-axis) will depend on absolute temperature (x-axis).

Accepted Answer

The answer of A reaction has a positive value of...

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

Which, if any, of the following processes is spontaneous under the specified conditions?

In a spontaneous process, the entropy of the system always increases.

Which relationship or statement best describes Δ\DeltaΔ S °\degree° for the following reaction? 2H2S(g) + 3O2(g) →\rightarrow→ 2H2O(g) + 2SO2(g)

A reaction has Δ\DeltaΔ G= 10.0 kJ and Δ\DeltaΔ G °\degree° = 15.0 kJ at a temperature of 50 °\degree° C. Calculate the value of the reaction quotient Q under these conditions.

For any reaction, if Δ\DeltaΔ G °\degree° > 0, then K < 1.

You are given pure samples of ethane, C2H6(g), and toluene, C7H8(l). What prediction would you make concerning their standard molar entropies at 298 K?

A reaction is proceeding towards equilibrium. At a certain stage, the concentrations of reactants and products are such that Δ\DeltaΔ G = Δ\DeltaΔ G °\degree° . What conclusion can reasonably be drawn about the reaction at this time?

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

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?

What is the free energy change, Δ\DeltaΔ G °\degree° , for the equilibrium between hydrogen iodide, hydrogen, and iodine at 453 °\degree° C? Kc = 0.020

Which relationship or statement best describes Δ\DeltaΔ S °\degree° for the following reaction? Pb(s) + Cl2(g) →\rightarrow→ PbCl2(s)

Given: H2O(l) →\rightarrow→ H2O(s), Δ\DeltaΔ H °\degree° = -6.02 kJ at 273K, calculate the entropy change of the surroundings ( Δ\DeltaΔ Ssurr) when one mole of water freezes at 0 °\degree° C and a pressure of one atmosphere.

The reaction of methane with water to form carbon dioxide and hydrogen is non-spontaneous at 298 K. At what temperature will this system make the transition from non-spontaneous to spontaneous? The data refer to 298 K.

Calculate Δ\DeltaΔ S °\degree° for the reaction

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

The free energy of a perfect crystal at absolute zero, is zero.

Calculate Δ\DeltaΔ G °\degree° for the combustion of propane.

A reaction has a positive value of Δ\DeltaΔ H °\degree° and a positive value of Δ\DeltaΔ S °\degree° . Draw a neat, labeled schematic plot to show how Δ\DeltaΔ G °\degree° (y-axis) will depend on absolute temperature (x-axis).

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 Mixtures: Solutions and Colloids

Periodic Patterns in the Main-Group Elements

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 Elements in Nature and Industry

The Transition Elements and Their Coordination Compounds

Nuclear Reactions and Their Applications

Filters

Which relationship or statement best describes $\Delta$ S $\degree$ for the following reaction? 2H₂S(g) + 3O₂(g) $\rightarrow$ 2H₂O(g) + 2SO₂(g)

A reaction has $\Delta$ G= 10.0 kJ and $\Delta$ G $\degree$ = 15.0 kJ at a temperature of 50 $\degree$ C. Calculate the value of the reaction quotient Q under these conditions.

For any reaction, if $\Delta$ G $\degree$ > 0, then K < 1.

You are given pure samples of ethane, C₂H₆(g), and toluene, C₇H₈(l). What prediction would you make concerning their standard molar entropies at 298 K?

A reaction is proceeding towards equilibrium. At a certain stage, the concentrations of reactants and products are such that $\Delta$ G = $\Delta$ G $\degree$ . What conclusion can reasonably be drawn about the reaction at this time?

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?

Which relationship or statement best describes $\Delta$ S $\degree$ for the following reaction? Pb(s) + Cl₂(g) $\rightarrow$ PbCl₂(s)

Given: H₂O(l) $\rightarrow$ H₂O(s), $\Delta$ H $\degree$ = -6.02 kJ at 273K, calculate the entropy change of the surroundings ( $\Delta$ S_surr) when one mole of water freezes at 0 $\degree$ C and a pressure of one atmosphere.

Calculate $\Delta$ S $\degree$ for the reaction $Calculate \Delta S \degree for the reaction$ $Calculate \Delta S \degree for the reaction$

Calculate $\Delta$ G $\degree$ for the combustion of propane. $Calculate \Delta G \degree for the combustion of propane.$ $Calculate \Delta G \degree for the combustion of propane.$

A reaction has a positive value of $\Delta$ H $\degree$ and a positive value of $\Delta$ S $\degree$ . Draw a neat, labeled schematic plot to show how $\Delta$ G $\degree$ (y-axis) will depend on absolute temperature (x-axis).