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Chemical Equilibrium Flashcards

1
Q

Front

A

Back

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2
Q

What is equilibrium in a broad sense?

A

“A state of a system where there is no observable change in the ‘properties’ of the system with respect to time.”

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3
Q

Give an example of physical equilibrium.

A

“A saturated solution where salt particles are dissolving and depositing at the same rate.”

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4
Q

Give an example of dynamic equilibrium.

A

“A volatile liquid in an air-tight container.”

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5
Q

What types of changes can dynamic equilibrium occur in?

A

“Physical change or a reversible chemical change.”

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6
Q

What is physical equilibrium?

A

“Equilibrium involving a physical change

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7
Q

What is chemical equilibrium?

A

“Equilibrium involving a chemical change

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8
Q

Why is a balanced see-saw an example of equilibrium?

A

“Because the two opposing processes (weight moving it clockwise and anticlockwise) are equal

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9
Q

What is a reversible reaction?

A

A reaction that can proceed in both the forward and backward directions.

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10
Q

How are reversible reactions represented?

A

By the sign ⇌ written between the reactants and products.

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11
Q

What happens to the rate of the forward reaction in a reversible reaction?

A

It starts fast and gradually slows down as reactants are used up.

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12
Q

What happens to the rate of the backward reaction in a reversible reaction?

A

It starts slowly and speeds up as products accumulate.

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13
Q

When is a reversible reaction in dynamic equilibrium?

A

When the forward and backward reactions occur at the same rate

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14
Q

What is a closed system?

A

A system where the reaction takes place in a closed container

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15
Q

Why is a closed system necessary for dynamic equilibrium?

A

Because in an open system

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16
Q

What is the Law of Mass Action?

A

It states that at constant temperature

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17
Q

How is active mass interpreted?

A

As the concentration of the substance raised to the power of its coefficient in the balanced equation.

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18
Q

What is the equilibrium constant (K)?

A

The ratio of the rate constants of the forward and backward reactions (k1/k2)

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19
Q

Does the equilibrium constant (K) change with temperature?

A

Yes

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20
Q

Does a catalyst change the value of K?

A

No.

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21
Q

What does Le Chatelier’s Principle state?

A

If an external constraint (change in temperature

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22
Q

What are the three main factors that affect equilibrium?

A

Temperature

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23
Q

If a reaction is endothermic

A

what is the sign of ΔH?

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24
Q

If a reaction is exothermic

A

what is the sign of ΔH?

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25
According to Le Chatelier's Principle
how will a decrease in temperature affect an equilibrium system?
26
According to Le Chatelier's Principle
how will an increase in temperature affect an equilibrium system?
27
How does increasing the temperature affect the equilibrium constant (K) for an endothermic reaction?
K increases
28
How does decreasing the temperature affect the equilibrium constant (K) for an endothermic reaction?
K decreases
29
For pressure changes to affect equilibrium
what must be true of the reaction?
30
How does increasing pressure affect an equilibrium system?
The equilibrium shifts to favor the reaction that reduces the number of gas molecules.
31
How does decreasing pressure affect an equilibrium system?
The equilibrium shifts to favor the reaction that increases the number of gas molecules.
32
Does a change in pressure change the equilibrium constant (K)?
No.
33
In an equilibrium mixture
what is the relationship between reactant and product concentrations?
34
What happens to equilibrium if more reactants are added?
The equilibrium shifts to the right
35
What happens to product concentration when equilibrium shifts to the right?
It increases proportionally.
36
Does adding more reactants change the equilibrium constant (K)?
No.
37
Besides adding reactants
how else can product formation be increased?
38
Does a catalyst change the position of equilibrium?
No.
39
What do catalysts affect in a reaction?
The time taken to reach equilibrium.
40
How does a positive catalyst affect the forward and backward reaction rates?
It increases both rates equally.
41
How does a positive catalyst affect the time to reach equilibrium?
It shortens the time.
42
How does a negative catalyst affect the rate of reaction?
It slows down the rate of reaction.
43
What happens to the energy change of a closed system at equilibrium?
It is at a minimum.
44
What is the state of a system at equilibrium in terms of stability?
It is most stable.
45
What is the relationship between the change in free energy (ΔG) and the equilibrium constant (K)?
ΔG = -RTlnK
46
What do R and T represent in the equation ΔG = -RTlnK?
R is the gas constant
47
In an electrochemical cell
where do oxidation and reduction occur?
48
What is the significance of Le Chatelier's Principle in the chemical industry?
It helps define optimum conditions for chemical processes and reduce undesirable reversibility.
49
Define 'active mass' in the context of the Law of Mass Action.
The concentration of a substance raised to the power of its coefficient in the balanced chemical equation.
50
What is the effect of a catalyst on the equilibrium constant?
It has no effect.
51
Explain the difference between a forward and a backward reaction.
A forward reaction proceeds from reactants to products
52
What is the relationship between the equilibrium constant (K) and the rate constants of the forward (k₁) and backward (k₂) reactions?
K = k₁/k₂
53
In the reaction N2(g) + 3H2(g) ⇌ 2NH3(g)
does high pressure favor the forward or reverse reaction?
54
In the reaction N2(g) + 3H2(g) ⇌ 2NH3(g)
why does high pressure favor the forward reaction?
55
In the reaction N2O4(g) ⇌ 2NO2(g)
does low pressure favor the forward or reverse reaction?
56
In the reaction N2O4(g) ⇌ 2NO2(g)
why does low pressure favor the forward reaction?
57
For a reaction with an equal number of gas molecules on both sides
does a change in pressure affect the equilibrium position?
58
What happens to the rate of a reaction at equilibrium?
The rate of the forward reaction equals the rate of the backward reaction.
59
Does equilibrium mean that the amounts of reactants and products are equal?
No
60
How does increasing the concentration of reactants affect the equilibrium position?
It shifts to the right
61
How does removing products from a reaction affect the equilibrium position?
It shifts to the right
62
What happens to the equilibrium position if you increase the concentration of a product in a reversible reaction?
It shifts to the left
63
In an exothermic reaction
does increasing the temperature favor product or reactant formation?
64
In an endothermic reaction
does increasing the temperature favor product or reactant formation?
65
What is the effect of a catalyst on the yield of products in a reversible reaction?
It has no effect.
66
What is the effect of increasing the concentration of a gaseous reactant on the rate at which equilibrium is attained?
It increases the rate.
67
In a reversible reaction
when is equilibrium reached?
68
Does the addition of an inert gas to a system at equilibrium change the equilibrium position?
Not usually
69
What is the effect of increasing temperature on the equilibrium constant (K) of an exothermic reaction?
It decreases.
70
What is the effect of increasing temperature on the equilibrium constant (K) of an endothermic reaction?
It increases.
71
In a reversible reaction
what is the state of free energy change (ΔG) at equilibrium?
72
What is the effect of increasing pressure on the rate of attaining equilibrium?
It increases the rate.
73
For a reversible reaction at equilibrium
what is the relationship between the rate of the forward reaction and the rate of the reverse reaction?
74
Does a catalyst affect the equilibrium constant?
No.
75
Does a catalyst change the position of equilibrium?
No.
76
How does a catalyst affect the rate of the forward and reverse reactions?
It increases both equally.
77
Does the equilibrium constant (K) change when the concentration of reactants or products is changed?
No.
78
What will happen to the concentrations of the other substances in the reaction if the concentration of one substance is increased?
The concentrations of the other substances will change in order to keep K constant.
79
If a reaction is exothermic
and you decrease the temperature
80
If a reaction is endothermic
and you increase the temperature
81
If you increase the pressure on a system where there are more gas molecules on the reactant side
what direction does the equilibrium shift?
82
Why is Le Chatelier's Principle important in the chemical industry?
It helps to define optimum conditions for chemical processes.
83
Why is Le Chatelier's Principle used in the chemical industry?
To reduce undesirable reversibility in reactions.
84
In an exothermic reaction
will a high temperature or a low temperature favor a high yield of product?
85
In an endothermic reaction
will a high temperature or a low temperature favor a high yield of product?

Chemistry (20 decks)

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