Deck 13: Spontaneous Processes and Thermodynamic Equilibrium

Question 1

Entropy has units of J·K^-1, therefore the Boltzmann constant has units equivalent to

A) J·K^-1
B) R
C) R/N_A
D) a and b
E) a and c

Answer 1

E

Question 2

Molar entropies have units of

A) J·K^-1
B) J·mol·K^-1
C) J·mol^-1·K^-1
D) TDH
E) b and d

Answer 2

C

Question 3

In going from a solid to a liquid, the entropy of a system will always

A) increase.
B) decrease.
C) remain constant so long as the phase transition takes place at a constant temperature.
D) be equal to the logarithm of the new number of microstates available.

Answer 3

A

Question 4

The evaporation of a liquid is

A) always spontaneous.
B) always associated with an increase in entropy.
C) a and b
D) None of the above

Question 5

An increase in entropy for a closed system is always associated with

A) an increase in the number of microstates available to the system.
B) an increase in the number of molecules in the system.
C) a and b
D) None of the above

Question 6

For an isentropic process

A) q=0
B) w=0
C) DS=0
D) a and c
E) b and c

Question 7

An element has a standard state molar entropy that is always

A) negative
B) zero
C) positive
D) not enough data to answer the question

Question 8

An element has a standard state molar Gibbs free energy that is always

A) negative
B) zero
C) positive
D) not enough data to answer the question

Question 9

Which of the following has a standard state Gibbs free energy equal to zero?

A) Br₂ (l)
B) I₂ (g)
C) C (s, diamond)
D) a and b
E) b and c

Question 10

Which of the following has a standard state entropy equal to zero?

A) Br₂ (l)
B) I₂ (g)
C) C (s, diamond)
D) a and b
E) b ad c
F) none of the above

Question 11

Which of the following is true for an equilibrium process?

A) DS_univ = 0
B) DS_univ < 0
C) DS_univ > 0
D) DS_sys = DS_surr
E) none of the above

Question 12

Which of the following is true for a spontaneous process?

A) DS_univ = 0
B) DS_univ < 0
C) DS_univ > 0
D) DS_sys = DS_surr
E) none of the above

Question 13

Which of the following equations are true for a system at thermodynamic equilibrium?

A) DH=TDS
B) DG=0
C) DH=-TDS
D) a and b
E) b and c

Question 14

A process can be spontaneous at low temperature but nonspontaneous at high temperature if

A) both DH and DS are positive
B) both DH and DS are negative
C) DH is positive and DS is negative
D) DH is negative and DS is positive
E) this can never happen

Question 15

Predict the sign of the entropy change for the following reaction
PCl₃(g) + Cl₂(g) → PCl₅(g)

A) positive
B) negative
C) zero
D) more data is needed to answer this question

Question 16

Predict the sign of the free energy change for the following reaction
PCl₃(g) + Cl₂(g) → PCl₅(g)

A) positive
B) negative
C) zero
D) more data is needed to answer this question

Question 17

Predict the sign of the entropy change for the following reaction
H₂(g) + I₂(g) → 2HI(g)

A) positive
B) negative
C) zero
D) more data is needed to answer this question

Question 18

As temperature increases, the value of DG_rxn for the following reaction will become
N₂(g) + 3H₂(g) → 2NH₃(g)

A) More positive
B) More negative
C) Not change
D) more data is needed to answer this question

Question 19

Calculate DS°_rxn for the following
NH₃(g) + HCl(g) → NH₄Cl(s)

A) 284.5 J·K^-1
B) -284.5 J·K^-1
C) -203.5 J·K^-1
D) 89.1 J·K^-1

Question 20

Calculate DS°_rxn for the following
3NO₂(g) + H₂O(l) → 2HNO₃(l) + NO(g)

A) 56.28 J·K^-1
B) -56.28 J·K^-1
C) 268.1 J·K^-1
D) -268.1 J·K^-1

Question 21

Acetone boils at 53°C. Using Trouton's rule, estimate acetone's molar enthalpy of vaporization.

A) 36.8 kJ
B) -16.7 kJ
C) 28.7 kJ
D) 4.66 kJ

Question 22

Exhibit 13-1
The following question(s) pertain to the reaction CCl₄(l) → CCl₄(g).
Refer to Exhibit 13-1. What is the value of DS°_vap?

A) 93.3 J·K^-1
B) -93.3 J·K^-1
C) 32.5 J·K^-1
D) -32.5 J·K^-1
E) None of the above

Question 23

Exhibit 13-1
The following question(s) pertain to the reaction CCl₄(l) → CCl₄(g).
Refer to Exhibit 13-1. What is value of DH°_vap?

A) 93.3 kJ
B) -93.3 kJ
C) 32.5 kJ
D) -32.5 kJ

Question 24

Exhibit 13-1
The following question(s) pertain to the reaction CCl₄(l) → CCl₄(g).
Refer to Exhibit 13-1. What is the predicted boiling point of CCl₄?

A) 85°C
B) 2400°C
C) 93°C
D) 113°C
E) None of the above

Question 25

Exhibit 13-1
The following question(s) pertain to the reaction CCl₄(l) → CCl₄(g).
Refer to Exhibit 13-1. Using Trouton's rule, what is the approximate boiling point of CCl₄?

A) 96°C
B) 787°C
C) 85°C
D) 110°C
E) None of the above

Question 26

The process I₂(s) → I₂(g) is spontaneous at 25°C?

Question 27

Can the reaction C(s, graphite) → C(s, diamond) ever be spontaneous?

Question 28

Exhibit 13-2
The following question(s) pertain to the reaction 2NO₂(g) → N₂O₄(g).
Refer to Exhibit 13-2. Is this reaction spontaneous at 25°C?

Question 29

Exhibit 13-2
The following question(s) pertain to the reaction 2NO₂(g) → N₂O₄(g).
Refer to Exhibit 13-2. As temperature increases, the value of DG_rxn will?

A) become more positive
B) become more negative
C) asymptotically approach the value of DH_rxn
D) equal the value of W
E) a and d

Question 30

Exhibit 13-2
The following question(s) pertain to the reaction 2NO₂(g) → N₂O₄(g).
Refer to Exhibit 13-2. At what temperature will the value of DG_rxn = 0?

A) For this reaction, DG can never equal zero
B) 0 K
C) 96°C
D) 53°C
E) None of the above

Question 31

Allotropic forms of an element that do not represent an element in its standard state will have

A) =
= 0
B) = 0,
positive
C) = 0,
positive
D) S°=0
E) None of the above

Question 32

A solid of mass m initially at T₀ is heated to T₁ at constant pressure where it proceeds to melt. Once all of the solid is in the liquid phase it is further heated to T₂. If the solid and liquid have specific heat capacities of c and c respectively, which equation below best represents the change in entropy for this system?

A)
B)
C)
D)
E) B and D

Question 33

The constant that connects the entropy of a system to the number of microstates is

A) R
B)
C) k_B
D)
E) B and C