Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

CHEM 1220 > Ch. 17: Gibbs Energy and Thermodynamics > Flashcards

Ch. 17: Gibbs Energy and Thermodynamics Flashcards

You may prefer our related Brainscape-certified flashcards:
AP® Chemistry flashcards Periodic Table flashcards Chemistry 101 flashcards Organic Chemistry 101 flashcards
1
Q

what is the fundamental goal of thermodynamics?

A

to predict spontaneity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

define spontaneous process

A

a process that occurs without ongoing outside intervention. Gibs energy is released in a spontaneous process

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

a mechanical system tends towards _____ _____ ____

A

lowest potential energy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

can spontaneity be effected by a catalyst?

A

no, catalysts only affect the rate of the reaction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

are non spontaneous reactions impossible?

A

no, they just do no occur without help

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

define entropy (S)

A

is a thermodynamic function that increases with the number of energetically equivalent ways to arrange the components of a system to achieve a particular state

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

define enthalpy(H)

A

the sum of the internal energy of a system and the product of its pressure and volume; the energy associated with the breaking and forming of bonds in a chemical reaction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

most spontaneous reactions are _____, but some spontaneous reactions are ____.

A

exothermic

endothermic

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

what is the symbol for entropy?

A

S

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

what is the mathematical expression that define entropy? define the terms used

A

S = k ln W

where. ..
- S is entropy
- k is the boltzmann constant (gas constant divided by Avogado’s number)
- W is the number of energetically equivalent ways to arrange the components of the system

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

what are the units for entropy?

A

J/K

Joules per Kelvin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

as W increases _____ increases

A

S or entropy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

a state in which a given amount of energy is more highly dispersed has ____ entropy than a state in which the same energy is more highly concentrated

A

more

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

what is the second law of thermodynamics?

A

for any spontaneous process, the entropy of the universe increases (ΔS universe> 0)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

what is the criterion for spontaneity?

A

an increase in the entropy of the universe

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

processes that _____ the entropy of the universe do no occur spontaneously

A

decrease

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

entropy is a state function which means…?

A

its value depends only on the state of the system, not on how the system arrived at that state

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

the change in entropy is equal to…?

A

the entropy of the final state minus the initial state

ΔS = S final - S initial

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

entropy determines the _____ of chemical and physical change

A

direction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

what direction does a chemical system proceed in?

A

in a direction that increases the entropy of the universe

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

define microstate

A

distribution of particles at any one instant

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

define macrostate

A

the given set of conditions (pressure, volume and temperature)

the state of the system

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

in general what changes in phase result in an increase in entropy?

A

solid to liquid
solid to gas
liquid to gas

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

in general, entropy increases as the number of moles of a gas _____ during a reaction

A

increases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

an exothermic process ____ the entropy of the surroundings

A

increases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

an endothermic process ____ the entropy of the surroundings

A

decreases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

what is the entropy change of the universe the sum of?

what is this in symbols?

A

the entropy changes for the system and the surroundings

ΔS universe = ΔS system + ΔS surroundings

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

the magnitude of increase in the entropy of the surroundings due to the dispersal of energy into the surroundings is ____ _____

A

temperature dependent

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

The greater the temperature, the _____ the increase in entropy for a given amount of energy dispersed into the surroundings

A

Smaller

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

Entropy is a measure of ____ ____ per unit ____

A 
Energy dispersal (joules)
Temperature (kelvins)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

Because entropy is directly proportional to ____ and inversely proportional to ____ when the surroundings are ____ adding energy will not make much difference to the entropy but when the surroundings are _____ then adding energy will make a big difference to the entropy (like giving a rich man money vs a poor man money. To the rich man it doesn’t make much difference but to the poor man it is life changing)

A

Energy dispersal
Temperature
Hot
Cold

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

In general, a process that emits heat into the surroundings (q system negative) ____ the entropy of the surroundings (positive ΔS surroundings)

A

Increases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

In general, a process that absorbs heat from surroundings (q system positive) _____ the entropy of the surroundings (negative ΔS surroundings)

A

Decreases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

In general, the magnitude of the change in entropy of the surroundings is ____ to the magnitude of q system

A

Proportional

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

What is the ΔS surroundings proportional to?

A
  • q system as well as 1/T
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

For any chemical reaction occurring at constant ____ and ____, the entropy change of the surroundings is equal to the ____ ____ into the surroundings (- ΔH system) divided by the ____ of the surroundings in kelvin

A

Temperature
Pressure
Energy dispersed
Temperature

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

Under conditions of constant pressure q system = …?

A
  • ΔH system
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

When is this equation true?

ΔS surroundings = (- ΔH surroundings) / (T)?

A

When pressure and temperature is constant

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

Define reversible process

A

a reaction that achieves the theoretical limit with respect to free energy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
40
Q

An ____ process decreases the entropy of the surroundings

A

Endothermic

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
41
Q

An ___ process increases the entropy of the surroundings

A

Exothermic

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
42
Q

what is the equation for gibbs energy?

A

ΔᵣG = ΔᵣH - TΔᵣS (at constant temp)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
43
Q

at constant temperature and pressure what is gibbs energy equal to?

A

ΔᵣG = -TΔSuniverse

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
44
Q

the change in gibbs energy for a process occuring at constant temperature and pressure is proportional to….?

A

the negative of change is entropy of the universe

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
45
Q

Gibbs energy is also called ….?

A

chemical potential

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
46
Q

when gibbs energy is greater than zero is the process spontaneous?

A

no

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
47
Q

when gibbs energy is less than zero is the process spontaneous?

A

yes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
48
Q

if a reaction is ___, and if the change in entropy for the reaction is _____, then the change in gibbs energy will be negative at all temperatures

A

exothermic

positive

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
49
Q

if a reaction is ___, and if the change in entropy for the reaction is _____, then the change in gibbs energy will be positive at all temperatures

A

endothermic

negative

50
Q

change in enthalpy is negative when….?

A

the reaction is exothermic/heat is emitted

51
Q

change in enthalpy is postive when…?

A

the reaction is endothermic/heat is absorbed

52
Q

an ____ reaction increases the entropy of the surroundings

A

exothermic

53
Q

when the entropy of the the surroundings and the system increase, the entropy of the universe ____

A

increases

54
Q

an ____ reaction decreases the entropy of the surroundings

A

endothermic

55
Q

when the entropy of the the surroundings and the system decrease, the entropy of the universe ____

A

decreases

56
Q

when ΔᵣH and ΔᵣS have the same sign the spontaneity depends on ____

A

the temperature

57
Q

what is the standard state for a pure gas?

A

a pressure of exactly one bar

58
Q

what is the standard state for a pure solid or liquid?

A

a pressure of one bar and the temperature of interest (often 25°C)

59
Q

what is the standard state for a substance in solution?

A

a concentration of 1 M

60
Q

define standard entropy change for a reaction (ΔᵣS°)

A

the change in entropy for a process in which all reactants and products are in their standard states

61
Q

define standard molar entropies (S°)

A

a measure of the energy dispersed into one mole of substance at a particular temperature

62
Q

when is entropy at absolute zero?

A

the entropy of a perfect crystal at absolute zero (0 K) is zero

63
Q

how many ways does a perfect crystal have to arrange itself?

A

one way (W=1)

64
Q

what does it mean when it is said that “entropy is an extensive” property?

A

it means that the entropy depends on the amount of substance

65
Q

In general, the entropy of a gas is ______ than the entropy of a liquid which is _____ than the entropy of a solid

A

greater

greater

66
Q

which has a greater affect on entropy, a state change from liquid to gas or an increase in molar mass?

A

a state change

67
Q

with increasing molar mass, entropy ______

A

increases

68
Q

why does entropy increase with molar mass____ for elements in the same state

A

the energy states associated with the motion of heavy atoms are more closely spaced than those of lighter atoms. the more closely spaced energy states allow for greater dispersal of energy at a given temperature, and therefore greater entropy.

69
Q

what two conditions are necessary for the trend of increasing entropy with increasing molar mass hold true?

A

when the temperatures is constant and when all atoms involved are in the same state

70
Q

what is an allotrope?

A

an element that can exist in two or more forms in the same state of matter

71
Q

what is a common allotrope?

A

carbon can exist in the solid form of diamond or graphite

72
Q

how do different allotropes differ in entropy?

A

the way in which they are chemically bonded can result in more or less disorder due to bond constraint or lack there of

73
Q

with increasing molar complexity, entropy _____

A

increases

74
Q

for a given state, molecules generally have ____ entropy than free atoms

A

greater

75
Q

what causes molecules to have greater entropy than free atoms?

A

free atoms only have transitional motion. molecules how ever have transitional motion, rotational motion and (at high enough temperatures) vibrational motion

76
Q

the dissolution of a crystalline solid into solution usually results in an ____ in entropy

A

increase

77
Q

how does the dissolution of a crystalline solid into a solution result in an increase in entropy?

A

when a solid is dissolved in a solution, the energy that was once concentrated within the crystal becomes dispersed throughout the entire solution. the greater energy dispersal results in greater entropy

78
Q

standard entropies are always _____ at 25°C

A

non-zero

79
Q

define standard change in Gibbs energy

A

the criterion for reactions spontaneity, calculated either from the standard changes in enthalpy and entropy or from tabulated values of Gibbs energies of formation

80
Q

the more ______ ΔᵣG° is, the more spontaneous the process (the further it will go toward ____ to reach equilibrium)

A

negative

products

81
Q

define Gibbs energy of formation (ΔfG°)

A

the Gibbs energy of formation is the change in Gibbs energy when 1 mole of a compound forms from its constituent elements in their standard states. the Gibbs energy of formation of pure elements in their standard states is zero

82
Q

the Gibbs energy of formation of pure elements in their standard states is ___

A

zero

83
Q

what is the spontaneity of a compound whose standard Gibbs energy of formation is negative?

A

spontaneous

84
Q

what is the spontaneity of a compound whose standard Gibbs energy of formation is positive?

A

non-spontaneous

85
Q

Compounds with negative Gibbs energy of formation are ____ common than compounds with positive Gibbs energy of formation

A

more

86
Q

If a chemical equation is multiplied by some factor, then ΔᵣG° is……?

A

also multiplied the same factor

87
Q

is a chemical equation is reversed, then ΔᵣG°……?

A

changes sign

88
Q

If a chemical equation can be expressed as the sum of a series of steps, then ΔᵣG° for the overall equation is…?

A

the sum of the Gibbs energies of reactions for each step

89
Q

the change in Gibbs energy of a chemical reaction represents…?

A

the maximum amount of energy available to do work (if ΔᵣG° is negative)

90
Q

the change in Gibbs energy for a chemical reaction represents the _____ _____ and is the maximum work that can be done by ______.

A

theoretical limit

reaction

91
Q

define reversible reaction

A

a reaction that achieves the theoretical limit with respect to free energy and will change direction upon an infinitesimally small change in a variable (such as temperature or pressure) related to the reaction.

92
Q

Why does water evaporate at room temperature when just left out on the counter when the Gibbs energy of the state change of water is positive?

A

the Gibbs energy is for standard conditions. In ordinary conditions the, the partial pressure of the water vapour is much less than atomsopheric pressure so the water evaporates. a partial pressure of one bar is standard condition

93
Q

What is the equation for Gibbs energy change under nonstandard conditions(ΔᵣG)?

A

ΔᵣG = ΔᵣG° + RT lnQ

94
Q

what is Q?

A

the reaction quotient

95
Q

what is the value of Q under standard conditions?

A

it is always one

96
Q

How is Q expressed for gasses?

A

in terms of pressure

units: bar

97
Q

How is Q expressed for solutes?

A

in terms of concentration

unit: mol/L or M

98
Q

what is the value of ΔᵣG at equilibrium?

A

it is always zero no matter the temperature

99
Q

what causes ΔᵣG to be zero at equilibrium?

A

because the value of RT lnQ will always be equal in magnitude and opposite in sign to the value of ΔᵣG

100
Q

what is the value of Q assumed to be for pure liquids and solids?

A

1

101
Q

when K > 1, lnK is _____ and ΔᵣG° is ____. Under standard conditions (when Q=1) the reaction is _____ in the _____ direction

A

positive
negative
spontaneous
forward

102
Q

when K > 1, lnK is _____

A

positive

103
Q

when K > 1, ΔᵣG° is ____

A

negative

104
Q

when K > 1 the reaction is _____ in the ____ direction, under standard conditions

A

spontaneous

forward

105
Q

when K=1, lnK is _____ and ΔᵣG° is ____. under standard conditions the reaction is….?

A

zero
zero
at equilibrium

106
Q

when K=1, lnK is _____

A

zero

107
Q

when K=1, ΔᵣG° is ____

A

zero

108
Q

when K=1, the reaction is….?

A

at equilibrium

109
Q

a state in which a given amount of energy is more highly dispersed has ____ entropy then a state in which the sane energy is more highly concentrated

A

more

110
Q

if the entropy of the system decrease what must be said about the entropy of the surroundings for the process to remain spontaneous?

A

the change in entropy in the surroundings (positive) should be greater than the loss of entropy of the system for spontaneity to occur

111
Q

∆G is proportional to the ____ of ∆suniverse

A

negative

112
Q

a decrease in Gibbs energy (∆G < 0) corresponds to a ____ process

A

spontaneous

113
Q

a increase in Gibbs energy (∆G > 0) corresponds to a ____ process

A

non spontaneous

114
Q

To calculate ∆ᵣSº, subtract the standard entropies if the ____ multiplied by their stoichiometric coefficients from the standard entropies of the ____ multiplied by their stoichiometric coefficients. what is this is equation form?

A

reactants
products
∆ᵣSº = ∑ np Sº (products) - ∑nr Sº (reactants)

115
Q

when temperature is not 298K what formula should you use to calculate ∆ᵣGº and why?

A

ΔᵣGº = ∆ᵣHº - T∆ᵣSº

this formula should be used because ∆ᵣHº and ΔᵣSº do not change much over a given change in temperature

116
Q

how do you calculate ΔᵣG° from the ∆ᵣGº of reactants and products? (give the equation)

A

∆ᵣGº = ∑ np Gº (products) - ∑nr Gº (reactants)

117
Q

the equilibrium constant becomes larger as the gibbs energy change becomes more _____

A

negative

118
Q

if the reactants undergo a large negative gibbs energy change as they become products, then the reaction will have a ____ equilibrium constant, with _____ strongly favoured at equilibrium

A

large

products

119
Q

if the reactants undergo a large positive gibbs energy change as they become products, then the reaction will have a ____ equilibrium constant, with _____ strongly favoured at equilibrium

A

small

reactants

120
Q

Spontaneity determines the ____ in which a reaction occurs and the ____ to which the reaction proceeds

A

direction

extent

CHEM 1220 (4 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions