Deck 9: Thermodynamics: the Second and Third Laws

Question 1

Calculate the change in molar entropy when 2.00 mol of ozone are compressed isothermally to one quarter of its original volume.Treat ozone as an ideal gas.

A)(-23.1 J.K ^{- 1} )
B)(-10.0 J.K ^{- 1} )
C)(-1.39 J.K ^{- 1} )
D)+10.0 J.K ^{- 1}
E)+23.1 J.K ^{- 1}

Answer 1

(-23.1 J.K ^{- 1} )

Question 2

The enthalpy of fusion of H₂O(s)at its normal melting point is 6.01 kJ.mol^-1.The entropy change for freezing 1 mol of water at this temperature is

A)+20.2 J.K^-1.mol^-1.
B)0 J.K^-1.mol^-1.
C)(-20.2 J.K^-1.mol^-1. )
D)+22.0 J.K^-1.mol^-1.
E)(-22.0 J.K^-1.molF^-1. )

Answer 2

(-22.0 J.K^-1.molF^-1. )

Question 3

Use Trouton's constant to estimate the enthalpy of vaporization of diethyl ether,which boils at 309 K.

A)+85 kJ.mol ^{- 1}
B)+26 kJ.mol ^{- 1}
C)+275 kJ.mol ^{- 1}
D)(-85 kJ.mol ^{- 1} )
E)(+3.6 kJ.mol ^{- 1} )

Answer 3

+26 kJ.mol ^{- 1}

Question 4

What is the change in entropy when the pressure of an ideal gas is increased at constant temperature? Choose from +,0,-.

Question 5

The change in molar entropy for vaporization of all liquids is about the same.True or false?

Question 6

Calculate the change in molar entropy when the pressure of argon is allowed to double isothermally (assume ideal behavior).

A)+1.39 J.K ^{- 1}.mol ^{- 1}
B)(-1.39 J.K ^{-- 1}.mol ^{- 1} )
C)(-4.16 J.K ^{- 1}.mol ^{- 1} )
D)(-5.76 J.K ^{- 1}.mol ^{- 1} )
E)+5.76 J.K ^{- 1}.mol ^{- 1}

Question 7

Use Trouton's constant to estimate the enthalpy of condensation of diethyl ether,which boils at 309 K.

A)(-26 kJ.mol ^{- 1} )
B)+26 kJ.mol ^{- 1}
C)(-275 kJ.mol ^{- 1} )
D)(-85 kJ.mol ^{- 1} )
E)+85 kJ.mol ^{- 1}

Question 8

The molar entropy of silver at 298 K is equal to the area under the curve obtained by plotting (from T = 0 to T = 298 K)

A)C_P versus T.
B)lnC_P versus T.
C)ln(C_P/T)versus T.
D)C_P/T versus T.
E)C_P versus 1/T.

Question 9

Calculate the standard entropy of vaporization of ethanol at its boiling point,352 K.The standard molar enthalpy of vaporization of ethanol at its boiling point is 40.5 kJ.mol ^{- 1}.

A)+40.5 kJ.K ^{- 1}.mol ^{- 1}
B)+115 J.K ^{- 1}.mol ^{- 1}
C)(-40.5 kJ.K ^{- 1}.mol ^{- 1} )
D)+513 J.K ^{- 1}.mol ^{- 1}
E)(-115 J.K ^{- 1}.mol ^{- 1} )

Question 10

All entropies of fusion are positive.True or false?

Question 11

Calculate the standard entropy of condensation of chloroform at its boiling point,335 K.The standard molar enthalpy of vaporization of chloroform at its boiling point is 31.4 kJ.mol^-1.

A)(-31.3 kJ.K^-1.mol^-1 )
B)+93.7 J.K ^{- 1}.mol ^{- 1}
C)(-93.7 J.K^-1.mol^-1 )
D)+31.4 kJ.K^-1.mol^-1
E)+506 J.K^-1.mol^-1

Question 12

The cooling of a hot metal is accompanied by an increase in entropy.True or false?

Question 13

Consider the following processes (treat all gases as ideal).
1.The pressure of 1 mole of oxygen gas is allowed to double isothermally.
2.Carbon dioxide is allowed to expand isothermally to 10 times its original volume.
3.The temperature of 1 mol of helium is increased 25 $\degree$ C at constant pressure.
4.Nitrogen gas is compressed isothermally to half its original volume.
"5.A glass of water loses 100 J of energy reversibly at 30 $\degree$ C.
Which of these processes lead(s)to an increase in entropy?"

A)1 and 4
B)5
C)3 and 5
D)2 and 3
E)1 and 2

Question 14

The molar heat capacity of Cu(s)at 1 atm pressure has been measured over a range of temperatures from close to 0 K to 400 K.Describe how you would obtain the standard molar entropy of Cu(s)at 298 K.

Question 15

Consider the following processes (treat all gases as ideal).
1.The pressure of 1 mol of oxygen gas is allowed to double isothermally.
2.Carbon dioxide is allowed to expand isothermally to 10 times its original volume.
3.The temperature of 1 mol of helium is increased 25 $\degree$ C at constant pressure.
4.Nitrogen gas is compressed isothermally to half its original volume.
"5.A glass of water loses 100 J of energy reversibly at 30 $\degree$ C.
Which of these processes lead(s)to a decrease in entropy?"

A)1 and 2
B)2
C)3 and 4
D)1, 4, and 5
E)1 and 3

Question 16

Calculate the normal boiling point of chloroform,given that the standard entropy and enthalpy of vaporization of chloroform is +93.7 J∙K ^{- 1}∙mol ^{- 1} and 31.4 kJ∙mol ^{- 1}.

Question 17

The temperature of 2.00 mol Ne(g)is increased from 25 $\degree$ C to 200 $\degree$ C at constant pressure.Calculate the change in the entropy of neon (assume ideal behavior).

A)+7.68 J.K ^{- 1}
B)+19.2 J.K ^{- 1}
C)(-7.68 J.K ^{- 1} )
D)(-19.2 J.K ^{- 1} )
E)+9.60 J.K ^{- 1}

Question 18

Calculate the standard entropy of fusion of ethanol at its melting point,159 K.The standard molar enthalpy of fusion of ethanol at its melting point is 5.02 kJ.mol ^{- 1}.

A)(-5.02 kJ.K ^{- 1}.mol ^{- 1} )
B)(-31.6 J.K ^{- 1}.mol ^{- 1} )
C)+5.02 kJ.K ^-1.mol^-1
D)+31.6 J.K^{- 1}.mol^{- 1}
E)(-44.0 J.K ^{- 1}.mol ^{- 1} )

Question 19

For a given transfer of energy,a greater change in disorder occurs when the temperature is high.True or false?

Question 20

Calculate the change in entropy of a large pail of water after 200 J of energy is reversibly transferred to the water at 20 $\degree$ C.

A)(-0.733 J.K ^{- 1} )
B)+0.683 J.K ^{- 1}
C)(-0.683 J.K ^{- 1} )
D)+0.733 J.K ^{- 1}
E)(-200 J.K ^{- 1} )

Question 21

Which of the following quantities is not equal to zero at 298 K?

A)( $\Delta$ H_f $\degree$ (H⁺(aq)))
B)S $\degree$ (H₂(g))
C)S $\degree$ (H⁺(aq))
D)( $\Delta$ G_f $\degree$ (H⁺(aq)))
E)( $\Delta$ H_f $\degree$ (H₂(g)))

Question 22

Which of the following has the smallest molar entropy?

A)C(diamond)
B)C₆₀(s)
C)CaCO₃(s)
D)CO₂(s)
E)C(graphite)

Question 23

Which of the following has the lowest standard molar entropy?

A)C(graphite)
B)P₄(s)
C)S₈(s)
D)C₆₀(s)
E)C(diamond)

Question 24

Which of the following has the smallest entropy at 298 K?

A)Kr(g)
B)Br₂(l)
C)Xe(g)
D)Cl₂(g)
E)Br₂(g)

Question 25

Which of the following has the smallest molar entropy at 298 K?

A)Cl₂(g)
B)N₂(g)
C)He(g)
D)F₂(g)
E)Ne(g)

Question 26

Which of the following reactions has the smallest value of $\Delta$ S $\degree$ ?

A)NH₃(g)+ HCl(g) $\rightarrow$ NH₄Cl(s)
B)2H₂(l)+ O₂(l) $\rightarrow$ 2H₂O(g)
C)N₂(g)+ 3H₂(g) $\rightarrow$ 2NH₃(g)
D)K(s)+ O₂(g) $\rightarrow$ KO₂(s)
E)BaCl₂.2H₂O(s) $\rightarrow$ BaCl₂(s)+ 2H₂O(g)

Question 27

Use the Boltzmann formula to calculate the entropy at T = 0 of 1.00 mol chlorobenzene,C₆H₅Cl,where each molecule can be oriented in any of six ways.

A)0 J.K ^{- 1}; at T = 0, there is no randomness.
B)(-15 J.K ^{- 1} )
C)(-30 J.K ^{- 1} )
D)+30 J.K ^{- 1}
E)+15 J.K ^{- 1}

Question 28

The molar entropy of Pb(s)at 298 K is equal to

A)C_P × 298.
B)zero.
C)the sum of the integral of C_PdT/T from 0 K to 298 K.

Question 29

Calculate $\Delta$ S_surr° at 298 K for the reaction 6C(s)+ 3H₂(g) $\rightarrow$ C₆H₆(l)
$\Delta$ H_r° = +49.0 kJ.mol ^{- 1}, $\Delta$ S_r° = -253 J.K ^{- 1}.mol ^{- 1}

A)+164 J.K ^{- 1}.mol ^{- 1}
B)(-417 J.K ^{- 1}.mol ^{- 1} )
C)+253 J.K ^{- 1}.mol ^{- 1}
D)(-164 J.K ^{- 1}.mol ^{- 1} )
E)(-253 J.K ^{- 1}.mol ^{- 1} )

Question 30

Which of the following is always true for a spontaneous process at constant temperature?

A)( $\Delta$ S_system + $\Delta$ S_surroundings = q/T)
B)( $\Delta$ S > 0)
C)( $\Delta$ S = q/T)
D)( $\Delta$ S_system + $\Delta$ S_surroundings > 0)
E)( $\Delta$ S < q/T)

Question 31

Calculate the standard entropy for the following reaction from standard molar entropies.
NH₄ClO₄(s)+ Al(s) $\rightarrow$ NH₄Cl(s)+ Al₂O_3(s)

Question 32

The experimental value of the molar entropy of 1 mol NO at 0 K is about 5 J∙K ^{- 1}.We can conclude that in the crystal the molecules of NO are arranged randomly.True or false?

Question 33

Which of the following has the largest molar entropy?

A)H₂(g)
B)KF(aq)
C)CO₂(s)
D)CaO(s)
E)He(l)

Question 34

Which of the following would probably have a positive $\Delta$ S value?

A)He(g, 2 atm) $\rightarrow$ He(g, 10 atm)
B)H₂(g)+ I₂(s) $\rightarrow$ 2HI(g)
C)2Ag(s)+ Br₂(l) $\rightarrow$ 2AgBr(s)
D)O₂(g) $\rightarrow$ O₂(aq)
E)2NO₂(g) $\rightarrow$ N₂O₄(g)

Question 35

For CO₂(g) $\rightarrow$ CO₂(aq),is the entropy change positive or negative?

Question 36

For He(g,10 atm) $\rightarrow$ He(g,1 atm),is the entropy change positive or negative?

Question 37

Calculate $\Delta$ S_surr $\degree$ at 298 K for the reaction H₂(g)+ F₂(g) $\rightarrow$ 2HF(g)
$\Delta$ H_r° = -546 kJ.mol ^{- 1}, $\Delta$ S_r° = +14.1 J.K ^{- 1}.mol ^{- 1}

A)+14.1 J.K ^{- 1}.mol^{- 1}
B)+1820 J.K ^{- 1}.mol ^{- 1}
C)+1830 J.K^-1.mol^-1
D)(-1830 J.K ^{- 1}.mol ^{- 1} )
E)(-14.1 J.K ^{- 1}.mol ^{- 1} )

Question 38

Sketch a plot of the molar entropy of oxygen gas from 0 K to 200 K.The normal melting and boiling points of oxygen are 55 K and 90 K,respectively.

Question 39

Calculate $\Delta$ S_total for the isothermal irreversible free expansion of 1.00 mol of ideal gas from 8.00 L to 20.00 L at 298 K.

A)0
B)+15.2 J.K ^{- 1}.molF ^{- 1}
C)+7.6 J.K ^{- 1}.mol ^{- 1}
D)(-15.2 J.K ^{- 1}.mol ^{- 1} )
E)(-7.6 J.K ^{- 1}.mol ^{- 1} )

Question 40

For the reaction is the entropy change positive or negative?

Question 41

The reaction 2Cu(s)+ CO₂(g) $\rightarrow$ 2CuO(s)+ C(s)
Is endothermic.Which of the following statements is true?

A)The reaction is not spontaneous at any temperature.
B)The reaction is spontaneous at all temperatures.
C)It is impossible to determine if the reaction is spontaneous without calculations.
D)The reaction will be spontaneous only at low temperatures.
E)The reaction will be spontaneous only at high temperatures.

Question 42

The entropy of fusion of water is +22.0 J.K^-1.mol^-1 and the enthalpy of fusion of water is +6.01 kJ.mol ^{- 1} at 0 $\degree$ C.At 0 $\degree$ C, $\Delta$ S_total for the melting of ice is

A)(-6010 J.K ^{- 1}.mol ^{- 1}. )
B)0.
C)(-22.0 J.K ^{- 1}.mol ^{- 1}. )
D)+6010 J.K ^{- 1}.mol ^{- 1}.
E)+22.0 J.K ^{- 1}.mol ^{- 1}.

Question 43

Calculate the standard free energy of formation of mercury(II)oxide at 298 K,given HgO(s)
Hg(l)
O₂(g)
-----------
$\Delta$ H_f°,kJ.mol ^{- 1}
-90.83
-
-
S_m°,J.K ^{- 1}.mol ^{- 1}
70.29
76.02
205.14

A)+58.5 kJ.mol ^{- 1}
B)+117.1 kJ.mol ^{- 1}
C)-58.5 kJ.mol ^{- 1}
D)-123.1 kJ.mol ^{- 1}
E)-117.1 kJ.mol ^{- 1}

Question 44

For the reaction 2SO₃(g) $\rightarrow$ 2SO₂(g)+ O₂(g)
$\Delta$ H_r° = +198 kJ.mol ^{- 1} and $\Delta$ S_r° = 190 J.K ^{- 1}.mol ^{- 1} at 298 K.The equilibrium constant for this reaction will be greater than 1 at

A)all temperatures.
B)temperatures above 1315 K.
C)temperatures below 1042 K.
D)no temperature.
E)temperatures above 1042 K.

Question 45

Under what conditions (e.g.,constant P)are the following relations true?
(a) $\Delta$ G = $\Delta$ H- T $\Delta$ S
(b)q = $\Delta$ H

Question 46

Consider the reaction Cl₂(g) $\rightarrow$ 2Cl(g)
Which of the following statement regarding this reaction is true?

A)The reaction is spontaneous at high temperatures.
B)The reaction is spontaneous at low temperatures.
C)The reaction is not spontaneous at any temperature.
D)The reaction is spontaneous at all temperatures.

Question 47

The reaction 2C(s)+ 2H₂(g) $\rightarrow$ C₂H₄(g)is endothermic.This reaction will not be spontaneous at any temperature.

Question 48

Which of the following statements is true?

A)Labile is a term that refers to the thermodynamic tendency of a substance to decompose.
B)A thermodynamically unstable compound is a compound with a positive standard free energy of formation.
C)Spontaneous reactions always have $\Delta$ S_r $\degree$ > 0.
D)Spontaneous reactions always have $\Delta$ G_r $\degree$ > 0.
E)Spontaneous reactions always have $\Delta$ H_r $\degree$ < 0.

Question 49

For the reaction 2C(s)+ 2H₂(g) $\rightarrow$ C₂H₄(g)
$\Delta$ H_r $\degree$ = +52.3 kJ.mol sup>- ¹ and $\Delta$ S_r $\degree$ = -53.07 J.K ^{- 1}.mol ^{- 1} at 298 K.The reverse reaction will be spontaneous at

A)temperatures below 985 K.
B)temperatures above 985 K.
C)temperatures below 1015 K.
D)all temperatures.
E)no temperatures.

Question 50

Consider the following compounds and their standard free energies of formation: Which of these liquids is (are)thermodynamically stable?

A)2 and 4
B)2 and 3
C)1, 3, and 5
D)1
E)3

Question 51

Consider the reaction 2SO₃(g) $\rightarrow$ 2SO₂(g)+ O₂(g)
Which statement is true for this reaction?

A)( $\Delta$ S < 0)
B)( $\Delta$ S > 0)
C)( $\Delta$ S = 0)
D)S_m^o = 0 for O₂(g)

Question 52

The reaction CH₃CH₂CH₂CH₃(g) $\rightarrow$ CH₃CH(CH₃)₂(g),is exothermic.This reaction will be spontaneous at high temperatures.

Question 53

The reaction N₂(g)+ 3H₂(g) $\rightarrow$ 2NH₃(g)is exothermic.This reaction will be spontaneous at all temperatures.

Question 54

For the reaction 2C(s)+ 2H₂(g) $\rightarrow$ C₂H₄(g)
$\Delta$ H_r $\degree$ = +52.3 kJ.mol ^{- 1} and $\Delta$ S_r $\degree$ = -53.07 J.K ^{- 1}.mol ^{- 1} at 298 K.This reaction will be spontaneous at

A)no temperature.
B)all temperatures.
C)temperatures below 985 K.
D)temperatures above 985 K.
E)temperatures below 1015 K.

Question 55

Calculate $\Delta$ G_r $\degree$ for the decomposition of mercury(II)oxide at 298 K. 2HgO(s) $\rightarrow$
2Hg(l)+
O₂(g)
------------
$\Delta$ H_f $\degree$ ,kJ.mol ^{- 1}
-90.83
S_m $\degree$ ,J.K ^{- 1}.mol ^{- 1}
70.29
76.02
205.14

A)-117.1 kJ.mol ^{- 1}
B)+246.2 kJ.mol ^{- 1}
C)-64.5 kJ.mol ^{- 1}
D)+117.1 kJ.mol ^{- 1}
E)-246.2 kJ.mol ^{- 1}

Question 56

The standard free energy of formation of benzene,C₆H₆(l),is +124.3 kJ.mol ^{- 1} at 298 K.This means that at 298 K benzene is thermodynamically unstable even though it can be kept indefinitely without decomposing.Explain.

Question 57

Consider the following compounds and their standard free energies of formation: Which of these liquids is (are)thermodynamically unstable?

A)2
B)1, 3, and 5
C)1 and 4
D)2 and 3
E)2 and 4

Question 58

Which one of the following statements is true?

A)Labile is a term that refers to the thermodynamic tendency of a substance to decompose.
B)Spontaneous reactions always have $\Delta$ G_r $\degree$ > 0.
C)Spontaneous reactions always have $\Delta$ H_r $\degree$ < 0.
D)Spontaneous reactions always have $\Delta$ S_r $\degree$ > 0.
E)A thermodynamically stable compound is a compound with a negative standard free energy of formation.

Question 59

For the reaction 2SO₃(g) $\rightarrow$ 2SO₂(g)+ O₂(g)
$\Delta$ H_r $\degree$ = +198 kJ.mol ^{- 1} at 298 K.Which statement is true for this reaction?

A)The reaction is driven by the enthalpy.
B)The reaction will not be spontaneous at low temperatures.
C)( $\Delta$ G_r $\degree$ will be negative at high temperatures.)
D)The reaction will not be spontaneous at any temperature.
E)( $\Delta$ G_r $\degree$ will be positive at high temperatures.)

Question 60

Estimate the minimum temperature at which magnetite can be reduced to iron by graphite. Fe₃O₄(s)+ 2C(s) $\rightarrow$ 2CO₂(g)+ 3Fe(s)
$\Delta$ S_r $\degree$ = +351.44 J.K ^{- 1}.mol ^{- 1}
The standard molar enthalpies of formation of magnetite and CO₂(g)are -118.4 and -393.51 kJ.mol ^{- 1},respectively.

A)670 $\degree$ C
B)Magnetite cannot be reduced by carbon at any temperature.
C)787 $\degree$ C
D)943 $\degree$ C
E)1790 $\degree$ C

Question 61

$\Delta$ U = 0 for the isothermal expansion of an ideal gas and therefore $\Delta$ S = -w_rev/T = nRln(V₂/V₁).True or false?

Question 62

Consider the compounds PCl₅(g),HCN(g),CuO(s),NO(g),NH₃(g),and SO₂(g).
Which compound will have approximately the same stability with respect to its elements if the temperature is raised?

A)CuO(s)
B)NO(g)
C)PCl₅(g)
D)HCN(g)
E)NH₃(g)

Question 63

Which of the following is true for a spontaneous reaction at constant temperature?

A)( $\Delta$ S + $\Delta$ H/T < 0)
B)( $\Delta$ G° = 0)
C)( $\Delta$ S_system < q/T)
D)( $\Delta$ H -T $\Delta$ S < 0)
E)( $\Delta$ S_surr > 0)

Question 64

Use tabulated thermodynamic data to calculate the concentration of CO₂(aq)in equilibrium with an external pressure of 2.50 atm CO₂(g)at 298 K.

Question 65

Use tabulated thermodynamic data to estimate the temperature at which the vapor pressure of benzene is 1.33 kPa.Hint: Assume that the enthalpy and entropy of the reaction are independent of temperature.

Question 66

Consider the compounds PCl₅(g),HCN(g),CuO(s),NO(g),NH₃(g),and SO₂(g).
Which compound will become more stable with respect to its elements if the temperature is raised?

A)SO₂(g)
B)CuO(s)
C)NH₃(g)
D)PCl₅(g)
E)NO(g)

Question 67

The entropy of vaporization of a substance is always larger than its entropy of fusion.True or false?

Question 68

All the following compounds become less stable with respect to their elements as the temperature is raised except

A)PCl₅(g).
B)C₆H₁₂(l).
C)N₂H₄(l).
D)CuO(s).
E)HCN(g).

Question 69

All the halogens exist as diatomic molecules at room temperature and 1 bar.Under these conditions,which of the halogens,F to I,has the smallest molar entropy?

Question 70

When calculating the entropy change as a result of transferring heat reversibly to or from a system,the temperature must be constant.True or false?

Question 71

For the reaction 2NH₃(g)→ 3H₂(g)+ N₂(g),K_P = 1.47 *10 ^{- 6} at 298 K.Estimate the temperature at which K_P = 0.0100.

Question 72

A piece of equipment must be capable of containing water at temperatures well above its normal boiling point.If the piece of equipment withstands an internal pressure of no more than 10.0 atm,calculate the highest temperature at which the system can be safely operated.

Question 73

Calculate $\Delta$ G for the process
He(g,1 atm,298 K) $\rightarrow$ He(g,10 atm,298 K)

Question 74

The sublimation of solid carbon dioxide is a spontaneous process.Predict the sign (+,-,or 0)of $\Delta$ G_r $\degree$$\Delta$ H_r $\degree$ and $\Delta$ S_r $\degree$ ,respectively.

A)(-, 0, +)
B)(-, -, -)
C)(-, +, +)
D)0, +, +
E)(-, +, -)

Question 75

An example of a spontaneous process having $\Delta$ H ~ 0 is

A)1 L He(1 atm, 298 K)+ 1 L Ar(1 atm, 298 K) $\rightarrow$ 2 L He/Ar mixture(1 atm, 298 K).
B)evaporation of water at 100 $\degree$ C and 1 atm.
C)a ball rolling from the top of a hill to the bottom of a valley.
D)precipitation of AgBr(s)from a solution of Ag⁺(aq)and Br ^- (aq).
E)freezing of water at -10 $\degree$ C.

Question 76

When calculating the entropy of vaporization of water at 25 $\degree$ C,the dominant contribution is

A)the molar heat capacity of liquid water.
B)heating the water from 25 $\degree$ C to 100 $\degree$ C.
C)cooling the water from 100 $\degree$ C to 25 $\degree$ C.
D)the entropy of vaporization of water at its normal boiling point.

Question 77

Calculate the entropy of vaporization of water at 25 $\degree$ C and 1 bar.The molar heat capacities of the liquid and gas are 75 and 34 J·K ^{- 1}·mol ^{- 1},respectively.The molar enthalpy of vaporization of water at its normal boiling point is 40.7 kJ·mol ^{- 1}.

Question 78

Which of the following statements is true?

A)If a reaction has $\Delta$ G_r $\degree$ = -275 kJ.mol ^{- 1}, it must proceed rapidly toward equilibrium.
B)All endothermic reactions are nonspontaneous.
C)The value of $\Delta$ G_r $\degree$ is not dependent on temperature.
D)A spontaneous reaction for which the entropy change is negative is entropy driven.
E)If a certain reaction is spontaneous, it is not spontaneous in the reverse direction.

Question 79

Consider the compounds PCl₅(g),HCN(g),CuO(s),NO(g),NH₃(g),and SO₂(g).
Which compound will become more stable with respect to its elements if the temperature is raised?

A)CuO(s)
B)PCl₅(g)
C)NH₃(g)
D)NO(g)
E)HCN(g)

Question 80

Which of the following statements is true?

A)The molar entropy does not depend on the structure of the compound.
B)The molar entropy of H₂O(l)is about the same as the molar entropy of ice.
C)An isothermal process that leads to a decrease in free energy is spontaneous.
D)If $\Delta$ G_r $\degree$ > 0, then the reaction is spontaneous.
E)All processes that give positive changes in energy are spontaneous.