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Chem II > ch 18 > Flashcards

ch 18 Flashcards

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1
Q

The Ksp of silver bromide is 5.4 × 10−13 at 298 K.
AgBr(s) Ag+(aq) + Br−(aq)

What is ΔrG°? (R = 8.314 J/K⋅mol)

A

e.

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2
Q

Estimate the boiling point of ethanol, C2H5OH, using the given the following thermodynamic parameters.

A

d.

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3
Q

Calculate the enthalpy of vaporization of water at its normal boiling point. ΔS° [H2O()] = 69.9 J/K⋅mol and ΔS° [H2O(g)] = 188.8 J/K⋅mol.

A

44.35 kJ/mol

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4
Q

When a real gas is compressed from low pressure to high pressure, its temperature increases. Which of the following is true for ΔH and ΔS?

A

a.

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5
Q

For any process, the change in entropy of the universe equals the sum of the entropy changes for the system and for the ________.

A

surroundings

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6
Q

Calculate the standard entropy change for the following reaction:
2 SO2(g) + O2(g) → 2 SO3(g)

Given: S°[SO2(g)] = 248.2 J/K⋅mol, S°[O2(g)] = 205.1 J/K⋅mol, and S°[SO3(g)] = 256.8 J/K⋅mol.

A

c.

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7
Q

Which of the following is true of a reaction that is product-favored?

A

a.

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8
Q

Which of the following is the second law of thermodynamics?

A

a.

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9
Q

Which of the following relationships is not true?

A

d.

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10
Q

Given the following data:
S(g) + O2(g) → SO2(g) ΔrG° = –300.1 kJ/mol-rxn
2 S(g) + 3 O2(g) → 2 SO3(g) ΔrG° = –742.1 kJ/mol-rxn
Calculate ΔfG° for the reaction below.
SO2(g) + 1/2 O2(g) → SO3(g)

A

b.

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11
Q

A reaction is said to be under thermodynamic control when _____.

A

a.

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12
Q

Hydrogen gas is prepared by electrolysis of water according to the reaction below.
2 H2O() → 2 H2(g) + O2(g)

Predict the signs of ΔrH and ΔrS.

A

a.

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13
Q

Using the given data, determine ΔrG° at 298 K for the precipitation reaction below.
Ag+(aq) +Br−(aq) → AgBr(s)

Substance ΔfG°(kJ/mol) at 298 K
Br−(aq)

–104.0

Ag+(aq)

77.12

AgBr(s)

–96.9

A

not c. or d. or .b

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14
Q

Given the following and that R = 8.314 J/K ⋅mol, determine the equilibrium constant, K, at 298K for the following reaction:
AgBr(s) → Ag+(aq) + Br−(aq)

Substance ΔfG°(kJ/mol) at 298 K
Br−(aq)

–104.0

Ag+(aq)

77.12

AgBr(s)
snot
–96.9

A

a.

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15
Q

Which of the following statements concerning entropy change is/are true?
1. For a reversible process, .
2. For a spontaneous process, .
3. For a reversible process, such as a phase change, ΔS = qrev/T .

A

d.

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16
Q

For a certain reversible process, q = 88.06 kJ at 29.4°C. Which of the following is the ΔS for the process?

A

b.

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17
Q

Arrange the following reactions in order of increasing ΔrS° value:
1. H2(g) + F2(g) → 2HF(g)
2. NH4NO3(s) → N2O(g) + 2H2O(l)
3. (NH4)2Cr2O7(s) → Cr2O3(s) + 4H2O(l) + N2(g)

A

not c

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18
Q

For the reaction Br2(l) → 2Br(g), _____.

A

a.

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19
Q

If a chemical reaction occurs in a direction that has a positive change in entropy, then _____.

A

e.

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20
Q

What is the equilibrium constant for the reaction below at 298 K?
2C(s) + 3H2(g) → C2H6(g)

Given: ΔrH° = –84.68 kJ; ΔrS° = –173.8 J/K at 298 K. (R = 8.314 J/K⋅mol)

A

a.

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21
Q

The change in entropy for any process is not dependent upon the pathway by which the process occurs. In other words, the change in entropy for any process is a(n) _____ function.

A

state

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22
Q

In which of the following reactions is ΔrS° expected to be positive?

A

e.

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23
Q

For a chemical reaction, if ΔrG° = 0, then _____.

A

e.

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24
Q

While diluting concentrated sulfuric acid with water, the temperature of the solution increases rapidly. What are the signs of ΔrH, ΔrS, and ΔrG for the process?

A

a.

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25
Q

What is the S0 for ozone if the standard entropy change for the reaction below is 411 J/K⋅mol-rxn and S0[O2(g)] = 205 J/K⋅mol.

A

c.

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26
Q

Which of the following changes lead to a decrease in entropy?

A

e.

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27
Q

The standard entropy for the formation of sulfur hexafluoride from the sulfur and fluorine is –348.7 J/K ⋅mol-rxn at 298.15 K. What is the standard molar entropy of sulfur hexafluoride for the reaction below? (Given: S°[S(s)] = 32.1 J/K ⋅mol and S°[F2(g)] = 202.8 J/K ⋅mol)

A

b.

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28
Q

For which of the following reactions will the entropy of a system decrease?

A

not b. or c.

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29
Q

The standard free energy change associated with the dissolution of ammonium nitrate in water is –6.73 kJ/mol at 298.15 K.

A

not b. or a. or e.

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30
Q

At what temperatures will a reaction be spontaneous if ΔrH° = +117 kJ and ΔrS° = –35 J/K?

A

e.

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31
Q

Which of the following is the equilibrium constant for the reaction below at 25 °C? (R = 8.314 J/K ⋅mol)
MgCO3(s) MgO(s) + CO2(g); ΔfG° [MgCO3(s)] = –1028.2 kJ/mol, ΔfG [MgO(s)] = –568.8 kJ/mol, and ΔfG° [CO2(g)] = –394.4 kJ/mol.

A

a.

32
Q

Determine ΔfG° at 298 K for SnO using the data below.
Sn(s) + SnO2(s) → 2SnO(s)

Given: ΔrG° = 12.0 kJ/mol-rxn at 298K.

Substance ΔfG°(kJ/mol) at 298 K
SnO(s)

?

SnO2(s)

–515.8

A

a.

33
Q

When a chemical process occurs under standard conditions, which of the following conditions always apply?
1. Gaseous species are at a pressure of 1 bar.
2. The solution concentration is 1 molal.
3. The temperature is 298.15 K.

A

d.

34
Q

Which of the following statements is/are correct?
1. Spontaneous changes only occur in the direction that leads to equilibrium.
2. Exothermic reactions are always spontaneous.
3. In any chemical reaction, energy must be conserved.

A

d.

35
Q

Which of the following compounds has the highest standard entropy per mole at 298 K?

A

c.

36
Q

A 100 mL sample of water is placed in a coffee cup calorimeter. When 1.0 g of an ionic solid is added, the temperature decreases from 21.5 °C to 20.8 °C as the solid dissolves. For the dissolving of the solid, _____.

A

b.

37
Q

Which of the following is true of the deposition of a gaseous substance?

A

d.

38
Q

If ΔrG° > 0 for a reaction at all temperatures, then ΔrH° is _____ and ΔrS° is _____.

A

b.

39
Q

Does the formation of complex molecules such as proteins and nucleic acids from more simple molecules contradict the second law of thermodynamics?

A

no it does not

40
Q

ΔG° = 0 for a reaction indicates that _____.

A

b.

41
Q

Which of the following linear chain alcohols is likely to have the highest standard entropy in the liquid state?

A

not d. or c.

42
Q

What is the sign of ΔH (system) and ΔS (system) if a chemical reaction is spontaneous only at lower temperatures under standard conditions?

A

a

43
Q

For a reaction, ΔrH° = –208.8 kJ and ΔrS° = –308.2 J/K. At what temperature will ΔrG° = 0.00 kJ?

A

b.

44
Q

Using the given data, determine ΔrG° at 500.0 K for the reaction below.
Ba(s) + H2O(g) → BaO(s) + H2(g)

Substance

ΔfH°(kJ/mol-rxn) at 298 K

S° (J/K·mol-rxn) at 298 K

Ba(s)

0

62.8

H2O(g)

–241.8

188.7

BaO(s)

–592

70.4

H2(g)

0

130.6

A

b.

45
Q

The standard free energy change for a chemical reaction is +13.3 kJ/mol. Which of the following is the equilibrium constant for the reaction at 125 °C? (R = 8.314 J/K⋅mol)

A

d.

46
Q

Calculate ΔrG° for the reaction below at 425 °C,
2 HI(g) H2(g) + I2(g); K = 0.018. (R = 8.314 J/K⋅mol)

A

d.

47
Q

The following processes occur spontaneously at 25 °C. Which of these processes is/are endothermic?
1. Ammonium nitrate, NH4NO3, dissolving in water (which is accompanied by a cooling of the water).
2. The expansion of a real gas into a vacuum (which is accompanied by a cooling of the gas).
3. Liquid water in an ice cube tray freezing into ice after being placed in a freezer.

A

d.

48
Q

Which of the following reactions would be expected to have a positive entropy change, ΔrS° > 0?

A

b.

49
Q

Calculate ΔS°(universe) for the combustion of acetylene at 298.15 K using the reaction below. (Given: ΔS°(system) = –194.6 J/K and ΔH°(system) = –2511.2 kJ)

A

not c. or b or d.

50
Q

For which of the following substances is the standard free energy of formation not equal to zero at 298 K?

A

not c. or b. or a.

51
Q

For the reaction given below, ΔH0 = −1516 kJ at 25°C and ΔS0 = −432.8 J/K at 25°C. This reaction is spontaneous _____.
SiH4(g) + 2 O2(g) → SiO2(s) + 2 H2O

A

a.

52
Q

A flask containing helium gas is released into a closed room. Which of the following ideas concerning entropy is/are true?

A

e.

53
Q

The standard free energy of formation of AgI(s) is –66.2 kJ/mol. ΔrG° for the reaction 2AgI(s) → 2Ag(s) + I2(s) is:

A

a.

54
Q

The total entropy of the universe is always increasing. This is a statement of the _____ law of thermodynamics.

A

second

55
Q

Which of the following represents the change in entropy for a system going from 142 possible microstates to 830 possible microstates? (k = 1.381 × 10-23 J/K)

A

d.

56
Q

What is the equilibrium constant for reaction below at 25 °C? (R = 8.314 J/K⋅mol)
2 NO(g) + O2(g) 2 NO2(g); ΔfG° [NO(g)] = +86.6 kJ/mol and ΔfG° [NO2(g)] = +51.2 kJ/mol.

A

c.

57
Q

Use the given thermodynamic data and the reaction below to calculate ΔS°(universe) for the formation of Fe2O3(s) at 298.15 K.

A

d.

58
Q

Which of the following statements concerning entropy is/are correct?
1. The entropy of a substance increases when converted from a liquid to a solid.
2. The entropy of a substance decreases as its temperature increases.
3. All substances have positive entropy values at temperatures above 0 K

A

e.

59
Q

Calculate ΔrG° for the reaction below at 25.0 °C.
CH4(g) + H2O(g) → 3 H2(g) + CO(g)

Given: ΔfG° [CH4(g)] = –50.8 kJ/mol, ΔfG° [H2O(g)] = –228.6 kJ/mol, ΔfG° [H2(g)] = 0.0 kJ/mol, and ΔfG° [CO(g)] = –137.2 kJ/mol.

A

c.

60
Q

Thermodynamics can be used to determine all of the following except _____.

A

d.

61
Q

In any chemical process, energy must be conserved. This is the _____ law of thermodynamics.

A

first

62
Q

Calculate ΔrG° at 25.0 °C for the reaction below.
2 Na(s) + 2 H2O() → 2 NaOH(aq) + H2(g)

Given: ΔrH° = −366.6 kJ/mol-rxn and ΔrS° = −154.2 J/K⋅mol-rxn

A

b.

63
Q

_____ changes only occur in the direction that leads toward chemical equilibrium.

A

spontaneous

64
Q

The dissolution of ammonium nitrate occurs spontaneously in water at 25 °C. As ammonium nitrate dissolves, the temperature of the water decreases. What are the signs of ΔrH, ΔrS, and ΔrG for this process?

A

c.

65
Q

Which of the following is the third law of thermodynamics as defined by Ludwig Boltzmann?

A

a.

66
Q

Which of the following statements concerning entropy is not correct?

A

d.

67
Q

If a chemical reaction is exothermic but not spontaneous, which of the following must be true?

A

e.

68
Q

If a cube of ice at 0 °C is placed outside on a warm summer day, the ice will melt spontaneously. What are the signs of ΔrH, ΔrS, and ΔrG for the process?

A

d.

69
Q

Which of the following is the first law of thermodynamics?

A

d.

70
Q

What is the standard entropy change for the following reaction?

A

a.

71
Q

Which of the following statements about entropy is true?

A

a.

72
Q

Calculate ΔG° at 298 K for the reaction below.
I2(g) + Br2(g) → 2IBr(g)

Given: ΔrH° = –11.6 kJ/mol-rxn; ΔrS° = 12 J/K⋅mol-rxn at 298 K.

A

c.

73
Q

At what temperatures will a reaction be spontaneous if ΔrH° = +62.4 kJ and ΔrS° = +301 J/K?

A

b.

74
Q

For a chemical system, ΔrG° and ΔrG are equal when:

A

b.

75
Q

At a temperature (in kelvin units) of _____, the entropy of a pure crystal is 0.0 J/K.

A

0 K

76
Q

Which of the following statements concerning the spontaneity of chemical and physical changes is correct?

A

e.

77
Q

A change of state occurring in a system is accompanied by 60.7 kJ of heat that is transferred to the surroundings at a constant pressure and at a constant temperature of 300 K. Calculate the ΔS(surroundings) for the process.

A

not d.

Chem II (13 decks)

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