Deck 15: Chemical Equilibrium

Question 1

Dynamic equilibrium is established when the rate of the forward reaction goes to zero.

Answer 1

False

Question 2

Since the equilibrium constant (
)is calculated using the numerical concentrations of reactants and products,
can never be a negative value.

Answer 2

True

Question 3

The rate of a chemical reaction is inversely proportional to the temperature.

Answer 3

False

Question 4

When dynamic equilibrium is achieved,the concentrations of reactants is equal to the concentrations of the products.

Question 5

The larger the equilibrium constant,the greater is the concentration of reactants relative to products at equilibrium.

Question 6

When dynamic equilibrium is achieved,the rates of the forward and backward reactions go to zero.

Question 7

The rate of a reaction increases with increasing concentrations of reactants because you have more collisions occurring in a given time period.

Question 8

Reaction rates generally increase as a reaction proceeds.

Question 9

The rate of a chemical reaction is the amount of reactant that changes to product in a specific amount of time.

Question 10

As long as
> 1,all reactants will eventually be consumed and leave us exclusively with product molecules.

Question 11

The Equilibrium Constant,
,is a way to quantify the relative concentrations of the reactants and products of a reaction at equilibrium.

Question 12

The rate of a chemical reaction always remains the same from start to finish.

Question 13

Collisions between reactant molecules do not always lead to the formation of product molecules.

Question 14

It is not necessary to have a balanced equation before writing an equilibrium constant expression.

Question 15

Equilibrium involves the ideas of sameness and constancy.

Question 16

Placing a [ ] around the formula of a chemical means that we are referring to the molar concentration of that chemical.

Question 17

A reversible reaction is one that can be stopped and then restarted as needed.

Question 18

A large equilibrium constant
indicates that the forward reaction is largely favored.

Question 19

Living things are in equilibrium with their surroundings.

Question 20

Dynamic equilibrium occurs when the rate of the forward reaction equals the rate of the reverse reaction.

Question 21

Adding heat to an exothermic reaction will cause the reaction to remain unchanged.

Question 22

Decreasing the amount of carbon dioxide in the reaction below will cause the reaction to proceed to the right so that equilibrium will be restored.

Question 23

Le Chatelier's principle states that when a chemical system at equilibrium is disturbed,the system shifts in a direction that minimizes the disturbance.

Question 24

A reaction that has
= 2.0 ×
will have high concentrations of products.

Question 25

If you have a chamber of gases at equilibrium,compressing the gases to half the original volume would have the same effect as doubling the pressure.

Question 26

If
equals about ≈1,then neither direction is favored and significant amounts of both reactants and products are present at equilibrium.

Question 27

In an exothermic reaction,you can consider the emitted heat as a reactant in this system.

Question 28

Decreasing the volume of the system below causes the reaction to shift towards the right.

Question 29

The equilibrium expression for the reaction:
.

Question 30

For a given chemical equation,the coefficients for each substance become the exponents for each substance in the written equilibrium expression.

Question 31

Increasing the amount of carbon in the reaction below will cause the reaction to proceed to the left so that equilibrium will be restored.

Question 32

The equilibrium expression for the reaction:
.

Question 33

If
= 2 for the reaction X ⇌ Y,then the
for Y ⇌ X will be 1/2 (or 0.5).

Question 34

A reaction that has
= 2.0 ×
will have high concentrations of products.

Question 35

Adding heat to an endothermic reaction causes the reaction to shift to the right.

Question 36

The equilibrium constant,
,for an equilibrium reaction will always be the same (at a given temperature)regardless of what the initial concentrations of reactants and products were.

Question 37

Le Chatelier's principle states that a chemical system must have a shift in direction in order to force the system to reach equilibrium.

Question 38

The equilibrium expression for the reaction:
.

Question 39

If the equilibrium constant,
,for a reaction increases upon heating,the reaction must have been endothermic.

Question 40

Increasing the volume of the system below causes the reaction to shift towards the right.

Question 41

Which of the following is TRUE for a system that is in dynamic equilibrium?

A)The forward reaction goes to 100% completion.
B)The reaction rate of the forward reaction approaches zero.
C)The concentration of products is equal to the concentration of the reactants.
D)Both the forward and reverse reactions come to a halt.
E)none of the above

Question 42

A compound with a very large
value is generally considered to be only partially soluble.

Question 43

The chemical equation that would generate the equilibrium expression
Is ________.(Assume all substances are gases in this reaction. )

A)C + 2B ⇌ 3A
B)3A ⇌ 2B + C
C)A ⇌ B + C
D)1/2 B + C ⇌ 1/3 A
E)none of the above

Question 44

For the reaction aA + bB ⇌ cC + dD,the equilibrium expression is:

A)
=

B)
=

C)
=

D)
=

E)none of the above

Question 45

A chemical equilibrium exists when:

A)reactants are completely changed to products.
B)there are equal amounts of reactants and products.
C)the rate at which reactants form products becomes zero.
D)the sum of reactant and product concentrations equals one mole.
E)the rate at which reactants form products is the same as the rate at which products form reactants.

Question 46

According to the collision theory of chemical reactions:

A)high energy collisions result in few successful reactions as there isn't sufficient time for the products to react.
B)low energy collisions result in many successful reactions as there is sufficient time for the reactants to form products.
C)high energy collisions lead to the successful formation of products.
D)low energy collisions do not occur in the gas phase.
E)all of the above

Question 47

Dissolving the compound PbCl₂ into water can be represented as
,so the equilibrium expression is Ksp =
.

Question 48

Why does the rate of the reaction decrease over time?

A)Exothermic reactions lose heat which cools the reaction which decreases reaction rate.
B)As the reaction proceeds,the concentration of the products results in fewer collisions.
C)As the reaction proceeds,a decrease in the concentration of reactants results in fewer successful collisions.
D)Not all molecules will react and some choose to stay in their present form.
E)none of the above

Question 49

Given N₂ (g)+ 3 H₂ (g)⇌ 2 NH₃ (g),which scenario will allow you to eventually reach an equilibrium mixture involving these chemicals?

A)Place only N₂ into a sealed vessel.
B)Place only H₂ into a sealed vessel.
C)Place only NH₃ into a sealed vessel.
D)All of the above scenarios.
E)none of the above

Question 50

For the reaction 2A + B ⇌ 2C + 3D,the equilibrium expression is:

A)
=

B)
=

C)
=

D)
=

E)none of the above

Question 51

Which of the following is TRUE about a chemical system in equilibrium?

A)No reaction takes place.
B)Temperature changes have no effect on reaction rate.
C)Addition of more reactants have no effect on reaction rate.
D)Reaction rate remains stable as long as temperature and pressure are stable.
E)none of the above

Question 52

A description of life is:

A)Living things maintain and control their sameness.
B)Living things maintain and control their changelessness.
C)Living things maintain and control their equilibrium.
D)Living things maintain and control their disequilibrium.
E)none of the above

Question 53

Which of the following changes will increase the reaction rate?

A)an increase in the concentration of the products
B)a decrease of the reaction temperature
C)allowing more time for the reaction
D)an increase in the concentration of reactants
E)all of the above

Question 54

Suppose a wall divides a playground,and twenty balls lie on the ground on the east side,while forty balls lie on the west side.If a child on the east side of the wall always tosses a ball over the wall at the same time a child on the west side tosses a ball over the wall,then:

A)equilibrium has been established.
B)all balls will eventually end up on one side.
C)equilibrium will be established once thirty balls are on each side.
D)this system can never reach equilibrium.
E)none of the above

Question 55

If an equilibrium reaction shifts to the right when the system is cooled,this indicates that the reaction is endothermic.

Question 56

Iron(II)carbonate (
= 3.07 × 10^-11)is more soluble than calcium fluoride (
= 1.46 × 10^-10).

Question 57

Which of the following changes will increase reaction rate?
1.An increase in the concentration of reactants
2.An increase in temperature
3.Higher-energy collisions between reacting molecules

A)1 and 2 only
B)1 and 3 only
C)2 and 3 only
D)All of 1,2,and 3
E)Neither 1,2,or 3

Question 58

A compound with a relatively small
value indicates that the compound is only partially soluble.

Question 59

A system is said to be in dynamic equilibrium when:

A)there is no longer any net change in the concentrations of products or reactants.
B)the forward and reverse reactions come to a halt.
C)the sum of the concentrations of the reactants is equal to the sum of the concentrations of the products.
D)you have let the reaction proceed for approximately 30 minutes and can assume there will be no more changes.
E)none of the above

Question 60

A catalyst speeds up a chemical reaction as it is being consumed.

Question 61

For the reaction
S(s)⇌ 2
(aq)+
(aq),what happens to the equilibrium position if ammonium sulfate is added?

A)shifts to the left
B)shifts to the right
C)does nothing
D)doubles
E)halves

Question 62

For the reaction
S(s)⇌ 2
(aq)+
(aq),the equilibrium expression is:

A)
=

B)
=

C)
= [

]²[

]
D)
= [

S]
E)none of the above

Question 63

For the reaction
S(s)⇌ 2
(aq)+
(aq),what happens to the equilibrium position if aqueous ammonium sulfide is added?

A)shifts to the left
B)shifts to the right
C)does nothing
D)doubles
E)halves

Question 64

What must be TRUE for a reaction possessing a large equilibrium constant?

A)The reaction rate is fast.
B)The reaction rate is slow.
C)The forward reaction is favored.
D)The reverse reaction is favored.
E)none of the above

Question 65

For the reaction
,the equilibrium concentrations are as follows:
M,
M.The equilibrium constant is:

A)1.0 ×
.
B)1.0 ×
.
C)1.0 ×
.
D)1.0 ×
.
E)none of the above

Question 66

Le Chatelier's Principle states that:

A)a disturbing force must be applied to a system in order for it to reach equilibrium.
B)when a system at equilibrium is disturbed,a new equilibrium constant is established.
C)when a chemical system at equilibrium is disturbed,the system shifts in order to minimize the effect.
D)when a chemical system is at equilibrium it is no longer possible to alter the system.
E)none of the above

Question 67

For the reaction

⇌ 2S
+
,the equilibrium expression is:

A)
=

B)
=

C)
=

D)
=

E)none of the above

Question 68

For the reaction
,
And the equilibrium concentration of silver ion is
M.What is

A)0.0038
B)9.6
C)2.6 ×
D)1.0
E)none of the above

Question 69

For the reaction
,
,and the equilibrium concentration of sulfide ion is
.What is

A)0.052 M
B)0.32 M
C)0.015 M
D)0.10 M
E)none of the above

Question 70

For the reaction
[

] = 0.12 M,

.The equilibrium constant is:

A)0.44
B)0.15
C)2.3
D)6.7
E)none of the above

Question 71

For the reaction 2 A ⇌ B,the equilibrium concentrations are as follows: [A] = 0.056 M and [B] = 0.12 M.Calculate the equilibrium constant (
)for the reaction.

A)2.6 × 10^-2
B)0.26
C)2.1
D)38
E)none of the above

Question 72

Which of the following is TRUE of a system for which
<< 1?

A)It will take a long time to reach equilibrium.
B)It will take a short time to reach equilibrium.
C)The equilibrium favors the reverse reaction.
D)The equilibrium favors the forward reaction.
E)none of the above

Question 73

Which of the following is TRUE of a system for which
>> 1?

A)It will take a short time to reach equilibrium.
B)It will take a long time to reach equilibrium.
C)The equilibrium favors the reverse reaction.
D)The equilibrium favors the forward reaction.
E)none of the above

Question 74

When writing the expression for an equilibrium constant,which type of substance IS included?

A)solids
B)pure liquids
C)gases
D)all of the above
E)none of these

Question 75

For the reaction
,the equilibrium concentrations are as follows:
,
,
.The equilibrium constant is:

A)7.53 ×
B)1.19 ×
C)8.43
D)1.33 ×
E)none of the above

Question 76

For the reaction 2 H₂O (l)⇌ 2H₂ (g)+ O₂ (g),the equilibrium expression is:

A)
= [H₂O]²
B)
= [H₂]² [O₂]
C)
=

D)
=

E)none of the above

Question 77

Which equilibrium constant represents a reaction that favors the formation of the products to the greatest extent?

A)
= 100
B)
= 1.0 ×

C)
= 1.0 ×

D)
= 1.0 ×

E)not enough information

Question 78

For the reaction LiOH (s)⇌ Li⁺ (aq)+ OH^- (aq),
= 4.6 ×
,and the equilibrium concentration for hydroxide ion is [OH^-] = 0.042 M.What is [Li⁺] at equilibrium?

A)0.11 M
B)0.0046 M
C)0.042 M
D)An answer cannot be determined without [LiOH] value.
E)none of the above

Question 79

Which equilibrium constant represents a reaction that favors the reactants to the greatest extent?

A)
= 100
B)
= 1.0 ×

C)
= 1.0 ×

D)
= 1.0 ×

E)not enough information

Question 80

Identify the equation for which
= [
]²[
].

A)
S(s)⇌

(aq)+ 2

(aq)
B)CuS(s)⇌
(aq)+

(aq)
C)

S(s)⇌

(aq)+


(aq)
D)
S(s)⇌ 2

(aq)+

(aq)
E)none of the above