5.2

Question 1

The Equilibrium Constant

Question 2

For a chemical equilibrium of the type:

Question 3

aA + bB cC + dD

Question 4

The value for K is given by:

Question 5

•The constant is dimensionless and its value changes with the

Question 6

temperature of the system.

Question 7

•Equilibrium expressions are always written with the products as

Question 8

the numerator and the reactants as the denominator. The

Question 9

exponents in the expression are the same as the coefficients in the

Question 10

balanced chemical equation.

Question 11

TRY:

Question 12

•It is used to predict the amounts of reactants and products at

Question 13

equilibrium

Answer 13

given the amounts of starting materials.

Question 14

Keg =

Question 15

Write the equilibrium expression for the following

Question 16

reaction.

Question 17

Ng(8)

Question 18

Keq =

Question 19

[AB

Question 20

Writing Equilibrium Expressions for

Question 21

Equilibrium Reactions

Question 22

+ 3H

Answer 22

(e) * 2NH

Question 23

Rule #1: Solids NEVER appear in equilibrium expressions.

Question 24

[SO.)

Question 25

2) AgN0

Question 26

Rule #2: Liquids and solvents NEVER appear in equilibrium

Question 27

expressions.

Question 28

[NH

Answer 28

]

Question 29

[N||H

Answer 29

|

Question 30

NH

Answer 30

an + H

Question 31

Therefore they are CONSTANT.

Question 32

Keg =

Question 33

WHY? The concentration of a pure solid/liquid is

Question 34

unchangeable.

Question 35

+ HCI

Question 36

3 (ag)

Question 37

Keq =

Question 38

What’s wrong with these examples?

Question 39

1) C

Answer 39

Ha) t+ H

Question 40

Keq =

Question 41

[C

Answer 41

H] H

Question 42

C

Answer 42

H

Question 43

ao)* AgCs + HNO3 (eq)

Question 44

Keg =

Question 45

LAgCiJ[HN 0

Answer 45

]

Question 46

[NH] [OH]

Question 47

[NH

Answer 47

)

Question 48

[AgNO

Answer 48

][HCI]

Question 49

[H

Answer 49

0]?

Question 50

[H

Answer 50

][0

Question 51

Calculating K

Answer 51

from Equilibrium Concentrations

Question 52

2NOC

Question 53

Solution:

Question 54

Place 2.00 mol of NOCI is a 1.00 L flask. At equilibrium

Question 55

you find 0.66 mol/L of NO. Calculate K

Question 56

Set up an ICE table of concentrations

Question 57

2NOCI → 2NO

Question 58

Initial conc. (mol/L)

Question 59

Change in conc. (mol/L)

Question 60

Equilibrium conc. (mol/L)

Question 61

Example (cont’d)

Question 62

•Calculate Kea

Question 63

+ C

Answer 63

(e

Question 64

2

Question 65

Keq =

Question 66

reverse procesS.

Question 67

[NOCI]

Question 68

[NOCH?

Question 69

(0.66)°(0.33)

Question 70

(1.34)²

Question 71

=0.080

Question 72

0

Question 73

using the equilibrium concentrations

Question 74

0.66

Question 75

+

Question 76

K’=

Question 77

NOTE: the equilibrium constant for the forward and

Question 78

reverse reactions are reciprocal values.

Question 79

→K’ represents the equilibrium constant for the

Question 80

-

Question 81

1

Question 82

d

Question 83

Keq

Question 84

0

Question 85

= 12.5

Question 86

Kea <1

Question 87

.. formation of REACTANT

Answer 87

NOCI

Question 88

REACTION) is favoured

Question 89

When written in reverse:

Question 90

.” Keq> 1

Question 91

2NOCI

Answer 91

→ 2NO

Question 92

.”.formation of PRODUCT (NOCI) is favoured

Question 93

Homogeneous/Heterogeneous Equilibria

Question 94

2NOe t C

Answer 94

(e)

Question 95

• Homgeneous equilibria: all the reactants and

Question 96

products are in the same phase.

Question 97

• Heterogeneous equilibria: more than one phase exists

Question 98

in a reaction mixture

Question 99

Remember that solids

Answer 99

liquids (and solvents) DO NOT

Question 100

appear in equilibrium expressions

Question 101

Example: Write the equilibrium law for the dissociation of

Question 102

NaOH

Answer 102

in water.

Question 103

The Magnitude of K

Question 104

eo

Question 105

→ 2NOCe)

Question 106

Very

Question 107

small

Question 108

eq

Question 109

equilibrium.

Question 110

NaOH * Na

Question 111

Key = [Na’][OH]

Question 112

eq

Question 113

• When K is very large (K»1)

Answer 113

the equilibrium lies very

Question 114

much to the right; products are favored.

Question 115

Reaction proceeds

Question 116

hardly at all.

Question 117

• If K is very small (K«1)

Answer 117

the equilibrium lies very

Question 118

much to the left; reactants are favored.

Question 119

Keq

Question 120

12.5

Question 121

+ OH (aq)

Question 122

(aq)

Question 123

• When K is neither very large nor very small (K= 1)

Question 124

neither reactants

Answer 124

nor products are favoured at

Question 125

10-3

Question 126

1

Question 127

109

Question 128

Appreciable concentrations

Question 129

of both reactants and products

Question 130

are present at equilibrium.

Question 131

9-10/11

Question 132

large

Question 133

Reaction proceeds

Question 134

nearly to completion.

Question 135

Kea <1

Question 136

.. formation of REACTANT

Answer 136

NOCI

Question 137

REACTION) is favoured

Question 138

When written in reverse:

Question 139

.” Keq> 1

Question 140

2NOCI

Answer 140

→ 2NO

Question 141

.”.formation of PRODUCT (NOCI) is favoured

Question 142

Homogeneous/Heterogeneous Equilibria

Question 143

2NOe t C

Answer 143

(e)

Question 144

• Homgeneous equilibria: all the reactants and

Question 145

products are in the same phase.

Question 146

• Heterogeneous equilibria: more than one phase exists

Question 147

in a reaction mixture

Question 148

Remember that solids

Answer 148

liquids (and solvents) DO NOT

Question 149

appear in equilibrium expressions

Question 150

Example: Write the equilibrium law for the dissociation of

Question 151

NaOH

Answer 151

in water.

Question 152

The Magnitude of K

Question 153

eo

Question 154

→ 2NOCe)

Question 155

Very

Question 156

small

Question 157

eq

Question 158

equilibrium.

Question 159

NaOH * Na

Question 160

Key = [Na’][OH]

Question 161

eq

Question 162

• When K is very large (K»1)

Answer 162

the equilibrium lies very

Question 163

much to the right; products are favored.

Question 164

Reaction proceeds

Question 165

hardly at all.

Question 166

• If K is very small (K«1)

Answer 166

the equilibrium lies very

Question 167

much to the left; reactants are favored.

Question 168

Keq

Question 169

12.5

Question 170

+ OH (aq)

Question 171

(aq)

Question 172

• When K is neither very large nor very small (K= 1)

Question 173

neither reactants

Answer 173

nor products are favoured at

Question 174

10-3

Question 175

1

Question 176

109

Question 177

Appreciable concentrations

Question 178

of both reactants and products

Question 179

are present at equilibrium.

Question 180

9-10/11

Question 181

large

Question 182

Reaction proceeds

Question 183

nearly to completion.