Deck 17: Thermodynamics: Entropy, free Energy, and Equilibrium

Question 1

Predict the sign of ΔS for each of the following processes,which occur at constant temperature. I.The volume of 2.0 moles of O₂(g)increases from 44 L to 52 L.
II.The pressure of 2.0 moles of O₂(g)increases from 1.0 atm to 1.2 atm.

A)I: ΔS = negative;II: ΔS = negative
B)I: ΔS = negative;II: ΔS = positive
C)I: ΔS = positive;II: ΔS = negative
D)I: ΔS = positive;II: ΔS = positive

Answer 1

I: ΔS = positive;II: ΔS = negative

Question 2

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

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.

Answer 2

I and II are both spontaneous.

Question 3

What is the entropy change associated with the expansion of one mole of an ideal gas from an initial volume of V to a final volume of V of 2.50V at constant temperature?

A)ΔS = 2.50 R ln (V_f/V_i)
B)ΔS = -2.50 R ln (V_f/V_i)
C)ΔS = R ln 2.50
D)ΔS = -R ln 2.50

Answer 3

ΔS = R ln 2.50

Question 4

The reaction A(g)→ B(g)is spontaneous under standard conditions.Which of the following statements must be true? I.The reaction B(g)→ A(g)is nonspontaneous under standard conditions.
II.A(g)will be completely converted to B(g)if sufficient time is allowed.
III.A(g)will be completely converted to B(g)rapidly.

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

Question 5

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

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

Question 6

Assume a heteronuclear diatomic molecule,AB,forms a one-dimensional crystal by lining up along the x-axis.Also assume that each molecule can only have one of six possible orientations,corresponding to atom A facing in either the positive or negative direction along the x-,y-,or z-axis.If the molecules are arranged randomly in the six directions,the molar entropy at absolute zero should be

A)R ln 6.
B)R ln 6⁶.
C)R ln 6!
D)0.

Question 7

What is k in Boltzmann's formula,S = k ln W?

A)the degeneracy of the state
B)the equilibrium constant for the process
C)the universal gas constant divided by Avogadro's number
D)the universal gas constant times Avogadro's number

Question 8

Which of the following statements is not true?

A)The reverse of a spontaneous reaction is always nonspontaneous.
B)A spontaneous process always moves toward equilibrium.
C)A nonspontaneous process cannot be caused to occur.
D)A highly spontaneous process need not occur rapidly.

Question 9

Which of the following processes is non-spontaneous at standard temperature and pressure?

A)Iron metal,oxygen,and water form rust (Fe₂O₃).
B)Melting of solid ice to ice water.
C)Diffusion of perfume molecules across a room.
D)A reaction at equilibrium moves to non-equilibrium.

Question 10

Which forward reaction is a nonspontaneous process?

A)the expansion of a gas into a vacuum
B)N₂(g)+ 3 H₂(g)⇌ 2 NH₃(g)if P_H₂ = P_N₂ = 1 atm,P_NH₃ = 0,and K_p = 4 × 10⁵
C)2 NH₃(g)⇌ N₂(g)+ 3 H₂(g)if P_NH₃ = 1 atm, P_H₂ = P_N₂ = 0,and K_p = 2 × 10^-6
D)None of these

Question 11

Sodium reacts violently with water according to the equation: 2 Na(s)+ 2 H₂O(l)→ 2 NaOH(aq)+ H₂(g)
The resulting solution has a higher temperature than the water prior to the addition of sodium.What are the signs of ΔH° and ΔS° for this reaction?

A)ΔH° is negative and ΔS° is negative.
B)ΔH° is negative and ΔS° is positive.
C)ΔH° is positive and ΔS° is negative.
D)ΔH° is positive and ΔS° is positive.

Question 12

The entropy change associated with the expansion of one mole of an ideal gas from an initial volume of V_i to a final volume of V_f at constant temperature is given by the equation,ΔS = R ln (V_f/V_i).What is the entropy change associated with the expansion of three moles of an ideal gas from an initial volume of V_i to a final volume of V_f at constant temperature?

A)ΔS = R ln (V_f/V_i)
B)ΔS = 3 mol × R ln (V_f/V_i)
C)ΔS = R ln (V_f × 2³/V_i)
D)ΔS = R ln (V_f × 3!/V_i)

Question 13

Entropy is a measure of

A)free energy.
B)the heat of a reaction.
C)molecular randomness.
D)the rate of a reaction.

Question 14

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

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

Question 15

The brown color associated with photochemical smog is due to NO₂(g),which is involved in an equilibrium with N₂O₄(g)in the atmosphere. 2 NO₂(g)⇌ N₂O₄(g)
Predict the signs of the enthalpy and entropy change for the forward reaction.

A)The enthalpy change is negative and the entropy change is negative.
B)The enthalpy change is negative and the entropy change is positive.
C)The enthalpy change is positive and the entropy change is negative.
D)The enthalpy change is positive and the entropy change is positive.

Question 16

What is the entropy of 10⁵ molecules in 10¹⁰ boxes?

A)1.59 × 10^-21
B)3.45 × 10^-20
C)1.38 × 10^-17
D)3.18 × 10^-17

Question 17

Without doing any calculations,determine whether the standard entropy change,ΔS° is positive or negative for each of the following reactions. reaction 1: C(graphite)+ O₂(g)→ CO₂(g)
Reaction 2: 2 CO(g)+ O₂(g)→ 2 CO₂(g)

A)ΔS° is positive for both reactions.
B)ΔS° is positive for reaction 1 but negative for reaction 2.
C)ΔS° is positive for reaction 2 but negative for reaction 1.
D)ΔS° is negative for both reactions.

Question 18

What is W in Boltzmann's formula,S = k ln W?

A)a fraction indicating the probability of obtaining a result
B)a random number
C)the number of ways of obtaining the state
D)the work times Avogadro's number

Question 19

The Boltzmann formula is S = k ln W.A perfect crystal has a molar entropy of 0 at absolute zero because

A)W = 0.
B)W = 1.
C)W = N_A.
D)k = 1.

Question 20

Without doing any calculations,determine whether the standard entropy change,ΔS° is positive or negative for each of the following reactions. reaction 1: S(s,rhombic)+ O₂(g)→ SO₂(g)
Reaction 2: 2 SO₂(g)+ O₂(g)→ 2 SO₃(g)

A)ΔS° is positive for both reactions.
B)ΔS° is positive for reaction 1 but negative for reaction 2.
C)ΔS° is positive for reaction 2 but negative for reaction 1.
D)ΔS° is negative for both reactions.

Question 21

For the process CaCO₃(calcite)→ CaCO₃(aragonite)ΔH° = -0.21 kJ,ΔS° = -4.2 J/K
Assuming that the surroundings can be considered a large heat reservoir at 25°C,calculate ΔS_surr and ΔS_total for the process at 25°C and 1 atm pressure.Is the process spontaneous at 25°C and 1 atm pressure?

A)ΔS_surr = 4.2 J/K,Δ_total = 0,not spontaneous
B)ΔS_surr = 0.7 J/K,ΔS_total = -3.5 J/K,not spontaneous
C)ΔS_surr = -0.7 J/K,ΔS_total = -4.9 J/K,spontaneous
D)ΔS_surr = -0.7 J/K,ΔS_total = -4.9 J/K,not spontaneous

Question 22

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

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 23

Calculate ΔS° for the following reaction. N₂(g)+ 2 O₂(g)→ 2 NO₂(g)

A)-156.5 J/K
B)-121.5 J/K
C)15.5 J/K
D)636.5 J/K

Question 24

The solubility of manganese(II)fluoride in water is 6.6 g/mL at 40°C and 4.8 g/L at 100°C.Based on these data,what is the sign of ΔH° and ΔS° for the process below? MnF₂(s)⇌ Mn²⁺(aq)+ 2 F^-(aq)

A)ΔH° is negative but the sign of ΔS° cannot be determined from this information.
B)ΔH° is negative and ΔS° is definitely negative.
C)ΔH° is positive but the sign of ΔS° cannot be determined from this information.
D)ΔH° is positive and ΔS° is definitely negative.

Question 25

For bromine,ΔH°vap = 30.91 kJ/mol and ΔS°vap = 93.23 JK^-1mol^-1 at 25°C.What is the normal boiling point for bromine?

A)25°C
B)58°C
C)124°C
D)332°C

Question 26

ΔS° = -198.7 J/K for the reaction shown below.Calculate S° for NH₃(g). N₂(g)+ 3 H₂(g)→ 2 NH₃(g)

A)61.7 J/K∙mol
B)123.4 J/K∙mol
C)192.3 J/K∙mol
D)384.6 J/K∙mol

Question 27

Which statement is true about the formation of CaCO₃(s)from CaO(s)and CO₂(g)at 1.00 atm? CaO(s)+ CO₂(g)→ CaCO₃(s) ΔH° = -178.7 kJ and ΔS° = -150.4 J/K

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

Question 28

Calculate ΔS° for the formation of three moles of solid sodium bromide from the elements at 25°C.

A)-350.1 J/K
B)-243.6 J/K
C)-121.5 J/K
D)260.4 J/K

Question 29

What is the sign of ΔS for each of the following processes? I.The separation of gaseous molecules of UF₆,into ²³⁸UF₆ and ²³⁵UF₆
At constant temperature and pressure.
II.The dissolving of I₂(s)in CCl₄(l).

A)ΔS is negative for I and negative for II.
B)ΔS is negative for I and positive for II.
C)ΔS is positive for I and negative for II.
D)ΔS is positive for I and positive for II.

Question 30

The standard molar entropy for Br₂(g)is 245.46 J/(mol ∙ K)at 25°C.Given that ΔS° = 104.58 J/K for the dissociation of one mole of Br₂(g)into Br(g)at 25°C,find the standard molar entropy for Br(g)at 25°C.

A)70.44 J/(mol ∙ K)
B)140.08 J/(mol ∙ K)
C)175.02 J/(mol ∙ K)
D)350.04 J/(mol ∙ K)

Question 31

For the reaction 3 C₂H₂(g)→ C₆H₆(l)at 25°C,the standard enthalpy change is -631 kJ and the standard entropy change is -430 J/K.Calculate the standard free energy change at 25°C.

A)948 kJ
B)-503 kJ
C)-618 kJ
D)-1061 kJ

Question 32

For a process to be at equilibrium,it is necessary that

A)ΔS_sys = ΔS_surr.
B)ΔS_sys = -ΔS_surr.
C)ΔS_sys = 0.
D)ΔS_sys = 0 and ΔS_surr = 0.

Question 33

At constant pressure and temperature,which statement is true?

A)All reactions for which ΔH < 0 are spontaneous.
B)All reactions for which ΔS < 0 are spontaneous.
C)All reactions for which ΔG < 0 are spontaneous.
D)All reactions for which K < 1 are spontaneous.

Question 34

Which of the following statements must be true for the entropy of a pure solid to be zero? I.The temperature must be 0 K.
II.The solid must be crystalline,not amorphous.
III.The solid must be perfectly ordered.
IV.The solid must be an element.

A)I
B)I and II
C)I,II,and III
D)I,II,III,and IV

Question 35

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

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

Question 36

Consider the reaction: N₂(g)+ 3 F₂(g)→ 2 NF₃(g) ΔH° = -249 kJ and ΔS° = -278 J/K at 25°C
Calculate ΔG° and state whether the equilibrium composition should favor reactants or products at standard conditions.

A)ΔG° = -332 kJ;the equilibrium composition should favor products.
B)ΔG° = -332 kJ;the equilibrium composition should favor reactants.
C)ΔG° = -166 kJ;the equilibrium composition should favor products.
D)ΔG° = -166 kJ;the equilibrium composition should favor reactants.

Question 37

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

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 38

For a spontaneous process

A)energy and entropy are conserved.
B)energy is conserved and the entropy of the system and surroundings increases.
C)the energy of the system and the surroundings decreases and the entropy of the system and surroundings increases.
D)both the energy and the entropy of the system and surroundings decrease.

Question 39

According to the third law of thermodynamics,

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 40

During perspiration,

A)the entropy of the water evaporated decreases and the entropy of the body decreases.
B)the entropy of the water evaporated decreases and the entropy of the body increases.
C)the entropy of the water evaporated increases and the entropy of the body decreases.
D)the entropy of the water evaporated increases and the entropy of the body increases.

Question 41

At high temperatures boron carbide vaporizes according to the equation B₄C(s)⇌ 4 B(g)+ C(s)
Which equation describes the relationship between ΔG° and ΔG for this reaction?

A)ΔG = ΔG° + R T ln (p_B ∙ [C]/[B₄C])
B)ΔG = ΔG° + R T ln p_B
C)ΔG = ΔG° + 4 R T ln p_B
D)ΔG = ΔG° - 4 R T ln p_B

Question 42

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

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

Question 43

Calculate the standard free energy for the reaction given. 2 CH₃OH(l)+ 3 O₂(g)→ 2 CO₂(g)+ 4 H₂O(l)

A)-465.2 kJ
B)-797.8 kJ
C)-1404.8 kJ
D)-2069.8 kJ

Question 44

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)

A)0.464 K
B)166 K
C)298 K
D)464 K

Question 45

For the evaporation of water during perspiration on a hot,dry day,

A)ΔH is positive and TΔS = ΔH.
B)ΔH is positive and TΔS > ΔH.
C)ΔH is positive and TΔS < ΔH.
D)ΔH is negative and TΔS is positive.

Question 46

For the reaction 3 C₂H₂(g)→ C₆H₆(l)at 25°C,the standard enthalpy change is -631 kJ and the standard entropy change is -430 J/K.Calculate the standard free energy change at 25°C?

A)-503 kJ
B)-10,120 kJ
C)619 kJ
D)-127 kJ

Question 47

For a reaction at constant temperature,as Q increases

A)ΔG and ΔG° increase.
B)ΔG and ΔG° decrease.
C)ΔG increases,but ΔG° remains constant.
D)ΔG decreases,but ΔG° remains constant.

Question 48

Which of the following are unstable with respect to their constituent elements at 25°C?

A)C₈H₁₈(l),CH₃OH(l)
B)C₈H₁₈(l),C₂H₂(g)
C)C₂H₂(g)
D)CH₃OH(l)

Question 49

Which of the following is true?

A)As a reaction at constant temperature and pressure goes to equilibrium,|ΔG| decreases.
B)The larger ΔG°,the faster the reaction.
C)The standard state for solutes is the pure solute at 1 atm.
D)When a reaction reaches equilibrium,ΔG° = 0.

Question 50

For any thermodynamic function Y,ΔY° for a reaction refers to the change in Y for the process in which

A)the mixed reactants at 1 atm go to equilibrium at 1 atm.
B)the separate reactants at 1 atm go to equilibrium at 1 atm.
C)the separate reactants in their standard states are completely converted to separate products in their standard states.
D)the spontaneous reaction occurs.

Question 51

The signs of ΔG,ΔH,and ΔS at 25°C are shown below for three reactions. reaction ΔG ΔH ΔS
I.- + +
II.- - +
III.- - -
Which reaction could go in the reverse direction at high temperature?

A)I
B)II
C)III
D)I and II

Question 52

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?

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 53

At 25°C,ΔG° = -198 kJ for the reaction,NO(g)+ O₃(g)⇌ NO₂(g)+ O₂(g). Calculate ΔG under the following conditions:

A)-159 kJ
B)-167 kJ
C)-198 kJ
D)-236 kJ

Question 54

A positive value of ΔG°_f for a solid compound at 25°C means the

A)compound cannot exist at 25°C and 1 atm.
B)compound must be a liquid or a gas at 25°C and 1 atm.
C)process of forming the compound from the elements is exothermic.
D)process of forming the compound from the stable elements at 25°C and 1 atm is nonspontaneous.

Question 55

Calculate the standard free energy change at 25°C for the reaction 2 NO(g)+ O₂(g)→ 2 NO₂(g).

A)-4.7 kJ
B)-72.6 kJ
C)-157.8 kJ
D)-532.6 kJ

Question 56

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.

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

Question 57

A reaction has ΔH° = -60.9 kJ/mol and ΔS° = 266.6 J/K.Is this reaction spontaneous or nonspontaneous? At what temperature (if any)can the spontaneity be reversed?

A)nonspontaneous,can be made spontaneous at 228 K
B)nonspontaneous,cannot be made spontaneous at any temperature
C)spontaneous,can be made nonspontaneous at 228 K
D)spontaneous,cannot be made nonspontaneous at any temperature

Question 58

Which is the lowest at 25°C?

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 59

Water can be made from elemental hydrogen and oxygen.Which equation can be used to determine ΔG_form from its elemental parts?

A)ΔG_form = Δ
- Δ

- Δ

B)ΔG_form = 2Δ
- 2Δ

- Δ

C)ΔG_form = Δ
- 2ΔG_H - ΔG_O
D)ΔG_form = 2Δ
+ Δ

- 2Δ

Question 60

Which equation can be used to determine ΔG_form for C₂H₅OH from its elemental parts.Be sure that the reaction is balanced.

A)ΔG_form = Δ
- ΔG_C - Δ

- Δ

B)ΔG_form = 2Δ
- 4ΔG_C - 6Δ

- Δ

C)ΔG_form = 2ΔG_C + 6ΔG_H + ΔG_O
D)ΔG_form = Δ
- 2ΔG_C - 3Δ

- Δ

Question 61

If ΔG° is negative for a reaction,

A)K < 0.
B)K = 0.
C)K is between 0 and 1.
D)K > 1.

Question 62

An ideal gas is expanded at constant temperature.What are the signs (+,-,or 0)of ΔH,ΔS,and ΔG for this system?

A)ΔH = +,ΔS = -,ΔG = +
B)ΔH = 0,ΔS = +,ΔG = -
C)ΔH = 0,ΔS = -,ΔG = +
D)ΔH = -,ΔS = +,ΔG = -

Question 63

What is the relationship between ΔG and the ΔG°_F for the reaction below? MgF₂(s)→ Mg²⁺(aq)+ 2 F^-(aq)

A)ΔG = {ΔG°_f [Mg²⁺ (aq)] + 2 ΔG°_f [F^- (aq)] - ΔG°_f [MgF₂ (s)]} + RT ln ([Mg²⁺] [F^-]²/[MgF₂])
B)ΔG = {ΔG°_f [Mg²⁺ (aq)] + 2 ΔG°_f [F^- (aq)] - ΔG°_f [MgF₂ (s)]} + RT ln ([Mg²⁺] [F^-])²)
C)ΔG = {ΔG°_f [Mg²⁺ (aq)] + 2 ΔG°_f [F^- (aq)]} + RT ln ([Mg²⁺] [F^-]²)
D)ΔG = {ΔG°_f [Mg²⁺ (aq)] + 2 ΔG°_f [F^- (aq)] - ΔG°_f [MgF₂ (s)]} + RT ln K_sp

Question 64

ΔG = ΔG° for a reaction

A)if Q = K.
B)if Q = 1.
C)at STP.
D)at the start of the reaction.

Question 65

If ΔG is small and positive,

A)the forward reaction is spontaneous and the system is far from equilibrium.
B)the forward reaction is spontaneous and the system is near equilibrium.
C)the reverse reaction is spontaneous and the system is far from equilibrium.
D)the reverse reaction is spontaneous and the system is near equilibrium.

Question 66

Calculate K_sp for PbI₂ at 25°C based on the following data:

A)4 × 10^-31
B)8 × 10^-18
C)9 × 10^-9
D)5 × 10^-5

Question 67

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.

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

Question 68

If Q increases,

A)ΔG increases and the reaction becomes more spontaneous.
B)ΔG increases and the reaction becomes less spontaneous.
C)ΔG decreases and the reaction becomes more spontaneous.
D)ΔG decreases and the reaction becomes less spontaneous.

Question 69

Which of the following must be true in order for this reaction to always proceed spontaneously?

A)K = Q
B)K > Q
C)K < Q
D)None of these,spontaneity is dependent on reaction conditions.

Question 70

The figure above represents the nonspontaneous reaction O₂(g)→ 2O(g).What are the signs (+ or -)of ΔH,ΔS,and ΔG for this process?

A)ΔH = +,ΔS = +,ΔG = +
B)ΔH = +,ΔS = +,ΔG = -
C)ΔH = -,ΔS = -,ΔG = +
D)ΔH = -,ΔS = -,ΔG = -

Question 71

At high temperatures,boron carbide vaporizes according to B₄C(s)⇌ 4 B(g)+ C(s)
At 2500 K,the equilibrium pressure of B(g)is 0.0342 mm Hg over a mixture of 0.300 mol B₄C(s)and 0.500 mol C(s).Calculate ΔG° for this process.

A)832 kJ
B)799 kJ
C)281 kJ
D)247 kJ

Question 72

Solid NaHCO₃ is heated to 90°C.At equilibrium the total pressure of the gases produced is 0.545 atm.Calculate ΔG° at 90°C for the reaction 2 NaHCO₃(s)⇌ Na₂CO₃(s)+ H₂O(g)+ CO₂(g).

A)-7.85 kJ
B)-3.67 kJ
C)+3.67 kJ
D)+7.85 kJ

Question 73

The figure represents the spontaneous deposition of iodine in which iodine vapor,I₂(g),becomes crystalline iodine solid I₂(s): I₂(g): → I₂(s).What are the signs (+ or -)of ΔH,ΔS,and ΔG for this process?

A)ΔH = +,ΔS = +,ΔG = +
B)ΔH = +,ΔS = +,ΔG = -
C)ΔH = -,ΔS = -,ΔG = +
D)ΔH = -,ΔS = -,ΔG = -

Question 74

If ΔG° is positive for a reaction,

A)K < 0.
B)K = 0.
C)K is between 0 and 1.
D)K > 1.

Question 75

The figure represents the spontaneous evaporation of nitrogen in which liquid nitrogen,N₂(l),becomes gaseous nitrogen,N₂(g): N₂(l)→ N₂(g).What are the signs (+ or -)of ΔH,ΔS,and ΔG for this process?

A)ΔH = +,ΔS = +,ΔG = +
B)ΔH = +,ΔS = +,ΔG = -
C)ΔH = -,ΔS = -,ΔG = +
D)ΔH = -,ΔS = -,ΔG = -

Question 76

What is the relationship between ΔG,Q_p,and K_p for a reaction involving gases?

A)ΔG = Q_p/K_p
B)ΔG = K_p/Q_p
C)ΔG = RTln(Q_p/K_p)
D)ΔG = RTln(K_p/Q_p)

Question 77

In figure (1)below argon atoms,represented by unshaded spheres,and neon atoms,represented by shaded spheres,are in separate compartments.Figure (2)shows the equilibrium state of the system after the stopcock separating the two compartments is opened.Assuming that argon and neon behave as ideal gases,what are the signs (+,-,or 0)of ΔH,ΔS,and ΔG for this process?

A)ΔH = +,ΔS = -,ΔG = +
B)ΔH = 0,ΔS = +,ΔG = -
C)ΔH = 0,ΔS = -,ΔG = +
D)ΔH = -,ΔS = +,ΔG = -

Question 78

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

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 79

When equilibrium is reached at constant temperature and pressure,

A)Q = 1.
B)ΔG° = 0.
C)S is maximized.
D)G is minimized.

Question 80

In figure (1)below oxygen molecules,represented by unshaded spheres,and chlorine molecules,represented by shaded spheres,are in separate compartments.Figure (2)shows the equilibrium state of the system after the stopcock separating the two compartments is opened.Assuming the oxygen and the chlorine behave as ideal gases,what are the signs (+,-,or 0)of ΔH,ΔS,and ΔG for this process?

A)ΔH = +,ΔS = -,ΔG = +
B)ΔH = 0,ΔS = +,ΔG = -
C)ΔH = 0,ΔS = -,ΔG = +
D)ΔH = -,ΔS = +,ΔG = -