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Chemistry > Chapter 18 > Flashcards

Chapter 18 Flashcards

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1
Q

Section 1

What is a reversible reaction?

A

A reaction where products can react to re-form the reactants.

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2
Q

Section 1

Are all chemical reactions reversible?

A

No, but most are under suitable conditions.

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3
Q

Section 1

When is a reversible reaction in chemical equilibrium?

A

When the forward and reverse reaction rates are equal, and reactant and product concentrations remain unchanged.

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4
Q

Section 1

What happens in a state of dynamic equilibrium?

A

The amounts of reactants and products remain constant, with both reactions continuing but no net change occurring.

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5
Q

Section 1

How is a chemical equation written to show equilibrium?

A

Using double arrows (⇌) to indicate the reaction is reversible.

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6
Q

Section 1

When will a reversible reaction reach equilibrium?

A

When temperature and concentration allow, unless a substance escapes or is removed.

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7
Q

Section 1

What does it mean when equilibrium “lies to the right”?

A

The forward reaction is favored, resulting in a higher concentration of products than reactants at equilibrium.

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8
Q

Section 1

What does it mean when equilibrium “lies to the left”?

A

The reverse reaction is favored, resulting in a higher concentration of reactants than products at equilibrium.

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9
Q

Section 1

What is the equilibrium expression?

A

nA + mB ⇆ xC + yD
Reactants (A and B) are at their maximum, while products (C and D) start at zero.

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10
Q

Section 1

How is equilibrium established in a reversible reaction?

A

When forward and reverse reaction rates become equal.

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11
Q

Section 1

Do reactions start out at equilibrium?

A

No.

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12
Q

Section 1

What is equal after equilibrium is reached?

A

The rates of the forward and reverse reactions are equal.

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13
Q

Section 1

Does the reaction stop at equilibrium?

A

No, both forward and reverse reactions continue at equilibrium, but there is no net change.

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14
Q

Section 1

Equilibrium will only be reached if the reaction is _________.

A

Reversible.

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15
Q

Section 1

True or false - If a reaction forms only a small amount of the products, it could be at equilibrium.

A

False, because equilibrium depends on the reaction conditions and the amounts of products and reactants.

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16
Q

Section 1

If a reaction forms a large amount of product before reaching equilibrium, the reaction is said to be _______.

A

Product-favored.

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17
Q

Section 1

When the reaction starts, what are the concentrations of the products?

A

The concentrations of the products (C and D) are zero.

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18
Q

Section 1

What happens to the concentrations of reactants and products after equilibrium is reached?

A

They undergo no further change if conditions remain the same.

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19
Q

Section 1

What remains constant at equilibrium?

A

The ratio of the concentrations.

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20
Q

Section 1

What is the equilibrium constant represented by?

A

The letter K.

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21
Q

Section 1

Is the equilibrium constant K dependent on the initial concentrations?

A

No, K is independent of the initial concentrations.

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22
Q

Section 1

What is the equilibrium constant K dependent on?

A

On the temperature of the system.

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23
Q

Section 1

What does it mean if K is equal to 1 at equilibrium?

A

It means that there are roughly equal concentrations of reactants and products.

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24
Q

Section 1

What does a small value of K indicate?

A

The reactants are favored.

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25
# Section 1 What does a large value of K indicate?
The products are favored.
26
# Section 1 What types of substances are included in the equilibrium constant K?
Only substances whose concentrations can change are included; pure solids and liquids are omitted.
27
# Section 1 What is the reverse reaction rate at time = 0?
There are no products to react.
28
# Section 1 When is the forward reaction rate the highest?
At the beginning of the reaction, when the concentrations of reactants are at their maximum.
29
# Section 1 The equilibrium constant for a given reaction can only change if ___.
The temperature changes.
30
# Section 1 A reaction with a large amount of reactants left at equilibrium would have a _______ K.
Small K.
31
# Section 2 What factors can shift the equilibrium position?
Changes in pressure, concentration, or temperature.
32
# Section 2 What does Le Châtelier’s principle state?
If a system at equilibrium is subjected to a stress, the equilibrium shifts in the direction that relieves the stress.
33
# Section 2 When does a change in pressure affect equilibrium?
Only in systems involving gases with different numbers of moles in reactants and products.
34
# Section 2 How does an increase in pressure affect equilibrium in a gaseous reaction?
The equilibrium shifts to the side with fewer moles of gas.
35
# Section 2 Why does equilibrium shift to the right when pressure increases in a gaseous reaction?
Shifting right reduces the total number of gas molecules, lowering the pressure.
36
# Section 2 What would happen in the reaction, if you had decreased the pressure instead of increased it?
The equilibrium would shift to the side with more gas molecules to compensate for the decrease in pressure.
37
# Section 2 What happens when the concentration of a reactant is increased in an equilibrium system?
It creates a stress on the equilibrium system, and the system will shift to produce more products to relieve the stress.
38
# Section 2 What will happen to the concentrations of A,B,C, and D if you add A to this system at equilibrium?
Changes in concentration have no effect on the value of the equilibrium constant.
39
# Section 2 What does high pressure favor in a reaction?
Reverse reaction.
40
# Section 2 What does low pressure favor in a reaction involving CO₂?
Formation of CO₂.
41
# Section 2 Why doesn't changing the amounts of CaO and CaCO₃ affect the equilibrium concentration of CO₂?
Because both CaO and CaCO₃ are solids, changing their amounts will not change the equilibrium concentration of CO₂.
42
# Section 2 What is the effect of temperature changes on a reversible reaction?
Reversible reactions are exothermic in one direction and endothermic in the other.
43
# Section 2 How does changing the temperature affect an equilibrium mixture?
The effect depends on which of the opposing reactions is endothermic and which is exothermic.
44
# Section 2 Which way will the reaction shift if you increase the temperature (add energy)?
The addition of energy in the form of heat shifts the equilibrium so that energy is absorbed. This favors the endothermic reaction. The removal of energy favors the exothermic reaction
45
# Section 2 What if you decrease the temperature?
The equilibrium will shift towards the exothermic reaction to release heat and counteract the change.
46
# Section 3 What is Ka?
Ka is the acid ionization constant, a higher Ka means a stronger acid.
47
# Section 3 What is the acid ionization constant (Ka) dependent on?
Ka is constant for a specified temperature but changes with each new temperature.
48
# Section 3 What species are present in an acetic acid solution?
CH₃COOH molecules, CH₃COO⁻ ions, and H₃O⁺ ions.
49
# Section 3 Why is water not included in the equilibrium expression for acid ionization?
Because water is the solvent.
50
# Section 3 What happens when sodium acetate (NaCH₃COO) is added to an acetic acid solution at constant temperature?
It disturbs the equilibrium.
51
# Section 3 What happens when sodium acetate is added to an acetic acid solution?
It disturbs the equilibrium
52
# Section 3 How does the concentration of hydronium ions change after adding sodium acetate?
The concentration of [H₃O⁺] decreases.
53
# Section 3 What happens to the concentration of acetic acid when sodium acetate is added?
The concentration of [CH₃COOH] increases.
54
# Section 3 Does the value of Ka change after adding sodium acetate?
No, Ka remains the same.
55
# Section 3 What is the effect on the pH when sodium acetate is added?
The pH decreases due to the lower concentration of hydronium ions.
56
# Section 3 What is the definition of a buffer?
A solution that resists changes in pH when small amounts of acids or bases are added.
57
# Section 3 What do buffered solutions contain?
Weak acids and salts of the weak acid.
58
# Section 3 How do buffered solutions react with acids or bases?
They can react with either, maintaining nearly constant pH.
59
# Section 3 What happens when small amounts of acids or bases are added to a buffered solution?
The pH remains nearly constant.
60
# Section 3 What happens when a small amount of base is added to an acetic acid, sodium acetate solution?
OH⁻ ions react with hydronium ions to form water, and acetic acid ionizes to replace the lost hydronium ions.
61
# Section 3 How can a weak base solution act as a buffer?
It contains a salt of the base, which helps resist pH changes.
62
# Section 3 Why are buffers important in the human body?
They help maintain blood pH between 7.3 and 7.5.
63
# Section 3 What type of reaction is the self-ionization of water?
An equilibrium reaction.
64
# Section 3 How are salts formed?
During the neutralization reaction between a Brønsted acid and a Brønsted base.
65
# Section 3 What ions are produced when a salt dissolves in water?
Positive cations from the base and negative anions from the acid.
66
# Section 3 What happens if the ions formed come from weak acids or bases?
They react with water, causing the pH to be different from 7.
67
# Section 3 What is hydrolysis?
A reaction between water molecules and ions of a dissolved salt.
68
# Section 3 What is anion hydrolysis?
When anions react with water, making the solution more basic.
69
# Section 3 What is cation hydrolysis?
Cations react with water, making the solution more acidic.
70
# Section 3 What is the anion of a salt in Bronsted terms?
The anion is the conjugate base of the acid and a proton acceptor.
71
# Section 3 What happens during anion hydrolysis in terms of hydroxide ion concentration?
An equilibrium is established that increases the hydroxide ion concentration [OH⁻] in the solution.
72
# Section 3 What happens during anion hydrolysis in terms of hydroxide ion concentration?
An equilibrium is established that increases the hydroxide ion concentration [OH⁻] in the solution.
73
# Section 3 Why are aqueous solutions of sodium carbonate strongly basic?
The carbonate ions react as a Bronsted base, increasing the hydroxide ion concentration.
74
# Section 3 What happens to the OH⁻ ion concentration in a sodium carbonate solution?
The OH⁻ ion concentration increases until equilibrium is established.
75
# Section 3 In the Bronsted sense, what is the role of the cation of a salt?
Conjugate acid of the base from which was formed and is a proton donor.
76
# Section 3 What happens if the base is weak in relation to the cation of a salt?
If the base is weak, the cation acts as an acid strong enough to donate a proton to a water molecule, forming 𝐻3𝑂+ ions.
77
# Section 3 What is the net effect of cation hydrolysis in an equilibrium?
The net effect of cation hydrolysis is an increase in the [𝐻3𝑂+] of the solution.
78
# Section 3 What are the four general categories of salts based on their hydrolysis properties?
-Strong acid-strong base -Strong acid-weak base -Weak acid-strong base -Weak acid-weak base
79
# Section 3 What type of solution do salts of strong acids and strong bases produce?
Neutral solutions, as neither the cation of a strong base nor the anion of a strong acid hydrolyzes appreciably.
80
# Section 3 What happens when salts formed from weak acids and strong bases dissolve in water?
The solution is basic because the anions of the salt are hydrolyzed by water, increasing the hydroxide ion concentration and raising the pH.
81
# Section 3 What type of solutions do salts of strong acids and strong bases produce?
Neutral solutions.
82
# Section 3 Do the cation of a strong base or the anion of a strong acid hydrolyze appreciably in aqueous solutions?
No.
83
# Section 3 What happens when salts from weak acids and strong bases dissolve in water?
The solution becomes basic, as anions of the dissolved salt are hydrolyzed, increasing the hydroxide ion concentration and raising the pH.
84
# Section 3 What happens when salts of strong acids and weak bases dissolve in water?
The solution becomes acidic, as cations of the dissolved salt are hydrolyzed, increasing hydronium ion concentration and lowering the pH.
85
# Section 3 What happens when salts of weak acids and weak bases dissolve in water?
The solution can be acidic, neutral, or basic, depending on the salt, as both ions of the salt are hydrolyzed extensively.
86
# Section 4 What is a saturated solution?
A saturated solution contains the maximum amount of solute possible at a given temperature in equilibrium with an undissolved excess of the substance.
87
Is a saturated solution always a concentrated solution?
No, a saturated solution is not necessarily a concentrated solution.
88
What equilibrium principles apply to all saturated solutions of sparingly soluble salts?
The equilibrium principles developed in the chapter apply to all saturated solutions of sparingly soluble salts.
89
What does the solubility product constant (Ksp) represent?
Product of ion concentrations in a saturated solution, each raised to its coefficient's power in the balanced equation.
90
What is excluded from the equilibrium expression when calculating Ksp?
The solid species (such as AgCl) is excluded from the equilibrium expression.
91
What can the numerical value of Ksp be determined from?
The numerical value of Ksp can be determined from solubility data.
92
What does the value of Ksp depend on?
The value of Ksp is constant for a given solid at a specific temperature.
93
Can the solubility of a solid be determined from Ksp?
Yes, the numerical value of Ksp can be determined from solubility data.
94
What is the relationship between Ksp and solubility?
Solubility is the amount of solid needed to form a saturated solution and can vary depending on conditions like the presence of a common ion.
95
Does the equilibrium condition require equal ion concentrations in a saturated solution?
No, equilibrium is reached when the ion product doesn't exceed the Ksp value, regardless of whether the ion concentrations are equal.
96
What happens if the ion product is less than Ksp?
The solution is unsaturated.
97
What happens if the ion product is greater than Ksp?
Solid precipitates.
98
How can the solubility product be used?
It can predict whether a precipitate forms when two solutions are mixed
99
What happens during precipitation?
Precipitation continues until the ion concentrations decrease to the point where the ion product equals Ksp.
100
What are the limitations of the solubility product principle (Ksp)?
-It's most useful for sparingly soluble substances. -It doesn't work well for moderately soluble or -very soluble substances due to significant ion attraction when ions are close together. -Sometimes, it requires considering two equilibria simultaneously.

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