Question 1

At 25°C,?G°f is -620 kJ/mol for SiCl4(g) and -592 kJ/mol for MgCl2(s) .Calculate ?G° for the reaction,SiCl4(g) + 2 MG(s)   →\rarr→  2 MgCl2(s) + Si(s) and determine if the reaction is spontaneous at 25°C if the pressure of SiCl4(g) is 1 atm.

Accepted Answer

A)  ?G° = 28 kJ;the process is spontaneous.
B)  ?G° = 28 kJ;the process is nonspontaneous.
C)  ?G° = -564 kJ;the process is spontaneous.
D)  ?G° = -564 kJ;the process is nonspontaneous.

Question 2

For the following reaction find Kp at 25°C and indicate whether Kp should increase or decrease as the temperature rises.
NH4HS(s) ⇌ H2S(g) + NH3(g) ΔH° = 83.47 kJ and ΔG° = 17.5 kJ at 25°C.

Accepted Answer

A)  Kp = 8.6 × 10-4 and Kp should increase as the temperature rises.
B)  Kp = 8.6 × 10-4 and Kp should decrease as the temperature rises.
C)  Kp = 1.2 × 103 and Kp should increase as the temperature rises.
D)  Kp = 1.2 × 103 and Kp should decrease as the temperature rises.

Question 3

Which of the following is a criterion for spontaneity that holds for any process?

Accepted Answer

A)  ΔG 
B)  ΔG > 0
C)  ΔStotal 
D)  ΔStotal > 0

Question 4

According to the third law of thermodynamics,

Accepted Answer

A)  energy is conserved in any transformation of matter.
B)  the entropy increases for any spontaneous process.
C)  the entropy of a perfectly ordered,crystalline substance is zero at 0 Kelvin.
D)  the entropy of the universe increases for any spontaneous process.

Question 5

A hot penny is dropped into cold water inside a polystyrene foam cup.Assuming negligible heat loss to the atmosphere and the cup,

Accepted Answer

A)  the decrease in entropy of the penny is equal to the increase in entropy of the water. ∣ ΔSpenny ∣ = ∣ ΔSwater ∣
B)  the decrease in entropy of the penny is less than the increase in entropy of the water. ∣ ΔSpenny ∣ water ∣
C)  the decrease in entropy of the penny is more than the increase in entropy of the water. ∣ ΔSpenny ∣ > ∣ ΔSwater ∣
D)  the entropy of both the penny and the water increases.

Question 6

The sign (+ or -)of ΔH is ________ and the sign (+ or -)of ΔS is ________ for the evaporation of water.

Accepted Answer

The answer of The sign (+ or -)of ΔH is...

Question 7

2(g) → 2O(g) ,which is nonspontaneous at 25°C.How will the spontaneity of this reaction vary with temperature? This reaction is A) nonspontaneous at all temperatures. B) nonspontaneous at high temperatures and spontaneous at low temperatures. C) spontaneous at high temperatures and nonspontaneous at low temperatures. D) spontaneous at all temperatures." class="answers-bank-image d-inline" rel="preload" >
-The figure above represents the reaction O2(g) → 2O(g) ,which is nonspontaneous at 25°C.How will the spontaneity of this reaction vary with temperature? This reaction is

Accepted Answer

A)  nonspontaneous at all temperatures.
B)  nonspontaneous at high temperatures and spontaneous at low temperatures.
C)  spontaneous at high temperatures and nonspontaneous at low temperatures.
D)  spontaneous at all temperatures.

Question 8

For the reaction below ΔG° = +33.0 kJ,ΔH° = +92.2 kJ,and ΔS° = +198.7 J/K.Estimate the temperature at which this reaction becomes spontaneous.
2 NH3(g) → N2(g) + 3 H2(g)

Accepted Answer

A)  0) 464 K
B)  166 K
C)  298 K
D)  464 K

Question 9

An electron in an oxygen p orbital on which of the following would have the highest entropy?

Accepted Answer

A)  CH3CH2OH
B)  CH3CH2O-
C)  CH3CO2OH
D)  CH3CO2-

Question 10

A reaction has ΔH° = 61.9 kJ/mol and ΔS° = 405.4 J/K.Is this reaction spontaneous or nonspontaneous? At what temperature (if any) can the spontaneity be reversed?

Accepted Answer

A)  nonspontaneous,can be made spontaneous at 153 K
B)  nonspontaneous,cannot be made spontaneous at any temperature
C)  spontaneous,can be made nonspontaneous at 153 K
D)  spontaneous,cannot be made nonspontaneous at any temperature

Question 11

-According to the diagram above,

Accepted Answer

A)  ΔG° is positive and is equal to a - b.
B)  ΔG° is positive and is equal to b - c.
C)  ΔG° is negative and is equal to b - c.
D)  ΔG° is negative and is equal to a - c.

Question 12

Why is the sign of ΔG rather than the sign of ΔStotal generally used to determine the spontaneity of a chemical reaction?

Accepted Answer

A)  ΔG can be used for processes that occur under any conditions.
B)  ΔG involves thermodynamic functions of the system only.
C)  Free energy is easier to understand than entropy.
D)  Entropy is based on probability and is therefore less reliable.

Question 13

The figure below represents the spontaneous reaction of H2 (shaded spheres) with O2 (unshaded spheres) to produce gaseous H2O. 2 (shaded spheres) with O2 (unshaded spheres) to produce gaseous H2O.   -How will the spontaneity of this reaction vary with temperature? This reaction is A) nonspontaneous at all temperatures. B) nonspontaneous at high temperatures and spontaneous at low temperatures. C) spontaneous at high temperatures and nonspontaneous at low temperatures. D) spontaneous at all temperatures." class="answers-bank-image d-inline" rel="preload" >
-How will the spontaneity of this reaction vary with temperature? This reaction is

Accepted Answer

A)  nonspontaneous at all temperatures.
B)  nonspontaneous at high temperatures and spontaneous at low temperatures.
C)  spontaneous at high temperatures and nonspontaneous at low temperatures.
D)  spontaneous at all temperatures.

Question 14

At 25°C,ΔH° = 1.895 kJ and ΔS° = -3.363 J/K for the transition
C(graphite) → C(diamond) 
Based on these data,

Accepted Answer

A)  graphite cannot be converted to diamond at 1 atm pressure.
B)  diamond is more stable than graphite at all temperatures at 1 atm.
C)  diamond is more stable than graphite below 290°C and graphite is more stable than diamond above 290°C.
D)  graphite is more stable than diamond below 290°C and diamond is more stable than graphite above 290°C.

Question 15

Which of the following processes are spontaneous?
I.dissolving more solute in an unsaturated solution
II.dissolving more solute in a saturated solution
III.dissolving more solute in a supersaturated solution

Accepted Answer

A)  none of these
B)  I
C)  I and II
D)  I,II,and III

Question 16

A reaction for which ΔH° = + 98.8 kJ and ΔS° = + 141.5 J/K is ________ (spontaneous or nonspontaneous)at low temperatures and ________ (spontaneous or nonspontaneous)at high temperatures.

Accepted Answer

nonspontan...

Question 17

Classify each of the following processes as spontaneous or nonspontaneous.
I.H2O(l) → H2O(g) T = 25°C,vessel open to atmosphere with 50% relative humidity
II.H2O(s) → H2O(l) T = 25°C,P = 1 atm

Accepted Answer

A)  I and II are both spontaneous.
B)  I is spontaneous and II is nonspontaneous.
C)  I is nonspontaneous and II is spontaneous.
D)  I and II are both nonspontaneous.

Question 18

At 2600 K,ΔG° = 775 kJ for the vaporization of boron carbide:
B4C(s) ⇌ 4 B(g) + C(s) 
Find ΔG and determine if the process is spontaneous if the reaction vessel contains 4.00 mol B4C(s) ,0.400 mol of C(s) ,and B(g) at a partial pressure of 1.0 × 10-5 atm.At this temperature,R T = 21.6 kJ.

Accepted Answer

A)  ΔG = -270 kJ;spontaneous.
B)  ΔG = -270 kJ;nonspontaneous.
C)  ΔG = -220 kJ;spontaneous.
D)  ΔG = -220 kJ;nonspontaneous.

Question 19

Which is the lowest at 25°C?

Accepted Answer

A)  ΔG°f for H2O (s) 
B)  ΔG°f for H2O (l) 
C)  ΔG°f for H2O (g) 
D)  1/2ΔG°f for O2 (g) plus ΔG°f for H2O (g)

Question 20

Which of the three laws of thermodynamics provides a criterion for spontaneity?

Accepted Answer

A)  the first law of thermodynamics
B)  the second law of thermodynamics
C)  the third law of thermodynamics
D)  both the second and third laws of thermodynamics

Exam 16: Thermodynamics: Entropy, free Energy, and Equilibrium

Why is the sign of ΔG rather than the sign of ΔStotal generally used to determine the spontaneity of a chemical reaction?

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An electron in an oxygen p orbital on which of the following would have the highest entropy?

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Which of the three laws of thermodynamics provides a criterion for spontaneity?

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A hot penny is dropped into cold water inside a polystyrene foam cup.Assuming negligible heat loss to the atmosphere and the cup,

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-According to the diagram above,

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A reaction for which ΔH° = + 98.8 kJ and ΔS° = + 141.5 J/K is ________ (spontaneous or nonspontaneous)at low temperatures and ________ (spontaneous or nonspontaneous)at high temperatures.

Correct Answerverifiednonspontan...View AnswerShow Answer

Which of the following is a criterion for spontaneity that holds for any process?

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For the following reaction find Kp at 25°C and indicate whether Kp should increase or decrease as the temperature rises. NH4HS(s) ⇌ H2S(g) + NH3(g) ΔH° = 83.47 kJ and ΔG° = 17.5 kJ at 25°C.

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The sign (+ or -)of ΔH is ________ and the sign (+ or -)of ΔS is ________ for the evaporation of water.

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The figure below represents the spontaneous reaction of H2 (shaded spheres) with O2 (unshaded spheres) to produce gaseous H2O. -How will the spontaneity of this reaction vary with temperature? This reaction is

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Which of the following processes are spontaneous? I.dissolving more solute in an unsaturated solution II.dissolving more solute in a saturated solution III.dissolving more solute in a supersaturated solution

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According to the third law of thermodynamics,

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At 25°C,ΔH° = 1.895 kJ and ΔS° = -3.363 J/K for the transition C(graphite) → C(diamond) Based on these data,

Correct AnswerverifiedShow Answer

At 2600 K,ΔG° = 775 kJ for the vaporization of boron carbide: B4C(s) ⇌ 4 B(g) + C(s) Find ΔG and determine if the process is spontaneous if the reaction vessel contains 4.00 mol B4C(s) ,0.400 mol of C(s) ,and B(g) at a partial pressure of 1.0 × 10-5 atm.At this temperature,R T = 21.6 kJ.

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A reaction has ΔH° = 61.9 kJ/mol and ΔS° = 405.4 J/K.Is this reaction spontaneous or nonspontaneous? At what temperature (if any) can the spontaneity be reversed?

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For the reaction below ΔG° = +33.0 kJ,ΔH° = +92.2 kJ,and ΔS° = +198.7 J/K.Estimate the temperature at which this reaction becomes spontaneous. 2 NH3(g) → N2(g) + 3 H2(g)

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At 25°C,?G°f is -620 kJ/mol for SiCl4(g) and -592 kJ/mol for MgCl2(s) .Calculate ?G° for the reaction,SiCl4(g) + 2 MG(s) →\rarr→ 2 MgCl2(s) + Si(s) and determine if the reaction is spontaneous at 25°C if the pressure of SiCl4(g) is 1 atm.

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Which is the lowest at 25°C?

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-The figure above represents the reaction O2(g) → 2O(g) ,which is nonspontaneous at 25°C.How will the spontaneity of this reaction vary with temperature? This reaction is

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Classify each of the following processes as spontaneous or nonspontaneous. I.H2O(l) → H2O(g) T = 25°C,vessel open to atmosphere with 50% relative humidity II.H2O(s) → H2O(l) T = 25°C,P = 1 atm

Correct AnswerverifiedShow Answer

Why is the sign of ΔG rather than the sign of ΔS_total generally used to determine the spontaneity of a chemical reaction?

Correct Answer
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A reaction for which ΔH° = + 98.8 kJ and ΔS° = + 141.5 J/K is (spontaneous or nonspontaneous)at low temperatures and (spontaneous or nonspontaneous)at high temperatures.

Correct Answer
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nonspontan...
View Answer

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For the following reaction find K_p at 25°C and indicate whether K_p should increase or decrease as the temperature rises. NH₄HS(s) ⇌ H₂S(g) + NH₃(g) ΔH° = 83.47 kJ and ΔG° = 17.5 kJ at 25°C.

Correct Answer
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The sign (+ or -)of ΔH is and the sign (+ or -)of ΔS is for the evaporation of water.

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The figure below represents the spontaneous reaction of H₂ (shaded spheres) with O₂ (unshaded spheres) to produce gaseous H₂O. -How will the spontaneity of this reaction vary with temperature? This reaction is

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At 2600 K,ΔG° = 775 kJ for the vaporization of boron carbide: B₄C(s) ⇌ 4 B(g) + C(s) Find ΔG and determine if the process is spontaneous if the reaction vessel contains 4.00 mol B₄C(s) ,0.400 mol of C(s) ,and B(g) at a partial pressure of 1.0 × 10^-5 atm.At this temperature,R T = 21.6 kJ.

Correct Answer
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Correct Answer
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For the reaction below ΔG° = +33.0 kJ,ΔH° = +92.2 kJ,and ΔS° = +198.7 J/K.Estimate the temperature at which this reaction becomes spontaneous. 2 NH₃(g) → N₂(g) + 3 H₂(g)

Correct Answer
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At 25°C,?G°_fis -620 kJ/mol for SiCl₄(g) and -592 kJ/mol for MgCl₂(s) .Calculate ?G° for the reaction,SiCl₄(g) + 2 MG(s) $\rarr$ 2 MgCl₂(s) + Si(s) and determine if the reaction is spontaneous at 25°C if the pressure of SiCl₄(g) is 1 atm.

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-The figure above represents the reaction O₂(g) → 2O(g) ,which is nonspontaneous at 25°C.How will the spontaneity of this reaction vary with temperature? This reaction is

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Classify each of the following processes as spontaneous or nonspontaneous. I.H₂O(l) → H₂O(g) T = 25°C,vessel open to atmosphere with 50% relative humidity II.H₂O(s) → H₂O(l) T = 25°C,P = 1 atm

Correct Answer
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