Deck 12: Reaction Rates and Chemical Equilibrium

Question 1

Which of the following will not increase the rate of a reaction?

A)decreasing the temperature
B)decreasing the concentration of the reactants
C)decreasing the surface area of the reactants
D)removing a catalyst
E)All of these will not increase the rate of a reaction.

Answer 1

All of these will not increase the rate of a reaction.

Question 2

The kinetics of a reaction is studied at 25 $\degree$ C and at 50 $\degree$ C.Which of the following statements is correct?

A)The rate of the reaction at 50 $\degree$ C will be lower than the rate at 25 $\degree$ C, since the molecules will be moving too fast to collide effectively.
B)The rate of the reaction at 50 $\degree$ C will be twice that of the rate at 25 $\degree$ C, since the temperature has doubled.
C)The rate of the reaction at 50 $\degree$ C will be greater than the rate at 25 $\degree$ C, since the activation energy will be lower at the higher temperature.
D)The rate of the reaction at 50 $\degree$ C will be greater than the rate at 25 $\degree$ C, since a greater fraction of the molecules will possess sufficient energy to react at the higher temperature.
E)None of these statements is correct.

Answer 2

The rate of the reaction at 50 $\degree$ C will be greater than the rate at 25 $\degree$ C, since a greater fraction of the molecules will possess sufficient energy to react at the higher temperature.

Question 3

In a chemical reaction at constant temperature, the addition of a catalyst

A)affects the equilibrium constant.
B)increases the average kinetic energy of the reactants.
C)provides an alternate reaction pathway with a different activation energy.
D)decreases the energy released in the chemical reaction.
E)increases the concentration of the products at equilibrium.

Answer 3

provides an alternate reaction pathway with a different activation energy.

Question 4

Identify the intermediate in the following two-step reaction.Cr²⁺(aq) + Sn⁴⁺(aq) ⇌Cr³⁺(aq) + Sn³⁺(aq) Cr²⁺(aq) + Sn³⁺(aq) $\rightarrow$ Cr³⁺(aq) + Sn²⁺(aq)

A)Sn³⁺(aq)
B)Sn⁴⁺(aq)
C)Sn²⁺(aq)
D)Cr²⁺(aq)
E)Cr³⁺(aq)

Question 5

Identify any intermediates or catalysts in the following two-step reaction: S₂O₈^2- + I^- $\rightarrow$ 2SO₄^2- + I⁺ I⁺ + I^- $\rightarrow$ I₂

A)S₂O₈^2- is an intermediate.
B)S₂O₈^2- is a catalyst.
C)I^- is a catalyst.
D)I⁺ is an intermediate.
E)SO₄^2- is a catalyst.

Question 6

Identify any intermediates in the following three-step reaction: H₂C=CH₂ + H₃O⁺ $\rightarrow$ H₃C=CH₂⁺ + H₂O H₃C=CH₂⁺ + H₂O $\rightarrow$ CH₃CH₂OH₂⁺ CH₃CH₂OH₂⁺ + H₂O $\rightarrow$ CH₃CH₂OH + H₃O⁺

A)H₃O⁺ is an intermediate.
B)H₃C=CH₂⁺ is an intermediate.
C)H₃C=CH₂⁺, CH₃CH₂OH₂⁺, and H₂O are intermediates.
D)CH₃CH₂OH₂⁺ is an intermediate.
E)H₂O is an intermediate.

Question 7

Identify the intermediate(s) in the following two-step reaction.O₃(g) ⇌ O₂(g) + O(g) O(g) + O₃(g) $\rightarrow$ 2O₂(g)

A)O(g)
B)O₃(g)
C)O₂(g)
D)O₂(g) and O(g)
E)O₃(g) and O₂(g)

Question 8

Which of the following changes will increase the fraction of collisions that are effective collisions?

A)increasing the temperature
B)increasing the concentration of the reactants
C)decreasing the concentration of the reactants
D)increasing the surface area of the reactants
E)All of these choices are correct.

Question 9

According to collision theory, the increase in the rate constant with increasing temperature is due mostly to the fact that

A)the activation energy decreases with increasing temperature.
B)the fraction of the collisions having sufficient energy to react increases with increasing temperature.
C)the pressure of the reactants increases with increasing temperature.
D)the heat change for most reactions is negative.
E)the fraction of the collisions that have the proper orientation for reaction increases with increasing temperature.

Question 10

Which of the following statements regarding catalysts is incorrect?

A)A catalyst increases the rate of a reaction by giving the reaction an alternate pathway with a lower activation energy.
B)Catalysts need not be present in large amounts because they are regenerated during the reaction.
C)Enzymes act as catalysts in our bodies.
D)In a chemical reaction, the catalyst is shown on the reactant side of the equation.
E)The shape of an active site on an enzyme is unique, allowing it to react with only one substrate.

Question 11

Identify any intermediates or catalysts in the following two-step reaction: H₂O₂ + 2Br^- + 2H⁺ $\rightarrow$ 2H₂O + Br₂ H₂O₂ + Br₂ $\rightarrow$ 2H⁺ + O₂ + 2Br^-

A)H₂O₂ is an intermediate.
B)H₂O₂ is a catalyst, Br^- is an intermediate.
C)Br^- is a catalyst, Br₂ is an intermediate.
D)H⁺ is a catalyst.
E)Br^- and H⁺ are catalysts, Br₂ is an intermediate.

Question 12

Identify the catalyst in the following three-step process for the decomposition of ozone.O₃(g) ⇌ O₂(g) + O(g) NO(g) + O₃(g) $\rightarrow$ NO₂(g) + O₂(g) O(g) + NO₂(g) $\rightarrow$ O₂(g) + NO(g)

A)O(g)
B)O₃(g)
C)O₂(g)
D)NO(g)
E)NO₂(g)

Question 13

The rate of a reaction can be increased by all of the following except

A)increasing the temperature.
B)increasing the concentration of the reactants.
C)increasing the surface area of the reactants.
D)adding a catalyst.
E)increasing the volume of the reaction vessel.

Question 14

Which of the following statements regarding catalysts is incorrect?

A)A catalyst increases the rate of a reaction by giving the reaction an alternate pathway with lower activation energy.
B)A catalyst is formed temporarily in an early step of a reaction.
C)Most enzyme catalysts are large protein molecules.
D)In a chemical equation the catalyst is shown above the reaction arrow of the equation.
E)The shape of an active site on an enzyme is unique, allowing it to react with only one substrate.

Question 15

Identify any intermediates or catalysts in the following two-step reaction: Cu²⁺ + H₂ $\rightarrow$ CuH⁺ + H⁺ CuH⁺ + H⁺ + H₂C=CH₂ $\rightarrow$ Cu²⁺ + H₃C-CH₃

A)CuH⁺ is an intermediate.
B)Cu²⁺ is a catalyst, H⁺ is an intermediate.
C)Cu²⁺ is a catalyst, CuH⁺ is an intermediate.
D)Cu²⁺ is a catalyst, CuH⁺ and H⁺ are intermediates.
E)CuH⁺ and H⁺ are catalysts, Cu²⁺ is an intermediate.

Question 16

Identify an intermediate in the following two-step reaction.Sn²⁺ + Fe³⁺ $\rightarrow$ Sn³⁺ + Fe²⁺ Sn³⁺ + Fe³⁺ $\rightarrow$ Sn⁴⁺ + Fe²⁺

A)Sn²⁺
B)Fe³⁺
C)Sn³⁺
D)Fe²⁺
E)Sn⁴⁺

Question 17

Factors that influence reaction rates include all of the following except the

A)magnitude of the equilibrium constant.
B)reaction temperature.
C)presence of a catalyst.
D)size of solid reactant particles.
E)concentration of reactants.

Question 18

Identify the intermediate(s) in the following three-step reaction.Cl₂(g) ⇌ 2Cl(g) CHCl₃(g) + Cl(g) $\rightarrow$ HCl(g) + CCl₃(g) CCl₃(g) + Cl(g) $\rightarrow$ CCl₄(g)

A)CHCl₃(g)
B)HCl(g)
C)Cl₂(g)
D)Cl(g)
E)Cl(g) and CCl₃(g)

Question 19

A catalyst speeds up a chemical reaction by

A)providing an alternate reaction pathway.
B)increasing the activation energy.
C)shifting the equilibrium.
D)increasing the heat of the reaction.
E)decreasing the heat of the reaction.

Question 20

When a chemical system has reached equilibrium:

A)the forward and reverse reactions have stopped
B)the rate of the forward reaction is greater than the rate of the reverse reaction.
C)the rate of the forward reaction is less than the rate of the reverse reaction.
D)the rate of the forward reaction is equal to the rate of the reverse reaction.
E)the equilibrium constant has reached a minimum.

Question 21

Consider the reaction CO(g) + H₂O(g) CO₂(g) + H₂(g), represented by the following diagram: What is the composition of this system when the reaction reaches equilibrium?

A)3 CO, 3 H₂O, 7 CO₂, 7 H₂
B)1 CO, 1 H₂O, 4 CO₂, 4 H₂
C)2 CO, 2 H₂O, 8 CO₂, 8 H₂
D)8 CO, 8 H₂O, 2 CO₂, 2 H₂
E)4 CO, 6 H₂O, 4 CO₂, 6 H₂

Question 22

Which of the following statements is correct for a reaction in which K_eq << 1?

A)The forward reaction is faster than the reverse reaction.
B)The reverse reaction is faster than the forward reaction.
C)There are more products than reactants at equilibrium.
D)There are more reactants than products at equilibrium.
E)None of these statements is correct.

Question 23

Given that evaporation is an endothermic process, which of the following sets of changes would cause the following system at equilibrium to shift to increase the number of I₂ molecules in the gas phase? I₂(s) ⇌ I₂(g)

A)Increasing container volume and increasing temperature
B)Increasing container volume and decreasing temperature
C)Decreasing container volume and increasing temperature
D)Decreasing container volume and decreasing temperature
E)Changing volume or temperature will not affect the number of gas molecules present at equilibrium

Question 24

Which equilibrium constant represents a reaction that is reactant favored?

A)K_eq = 0.025
B)K_eq = 5.2
C)K_eq = 8.4 x 10^-5
D)K_eq = 6.3 x 10⁵
E)not enough information

Question 25

The graph shows the change in concentrations of the reactant and product as a reaction proceeds.At what point is equilibrium first reached?

A)I
B)II
C)III
D)IV
E)V

Question 26

The amount of energy that reactant molecules must possess in order to react is the activation energy.

Question 27

Consider the following reaction carried out in a sealed container: N₂(g) + 3H₂(g) ⇌ 2NH₃(g) A state of equilibrium can be reached if the container initially contains

A)NH₃ only.
B)N₂ and H₂ only.
C)NH₃ and N₂ only.
D)NH₃, N_2, and H₂.
E)any of these combinations of reactants and product.

Question 28

A reaction that has a high activation energy will have a high rate of reaction.

Question 29

Which of the following statements is correct for a reaction in which K_eq >> 1?

A)The forward reaction is faster than the reverse reaction.
B)The reverse reaction is faster than the forward reaction.
C)There are more products than reactants at equilibrium.
D)There are more reactants than products at equilibrium.
E)None of these statements is correct.

Question 30

Which equilibrium constant represents a reaction that is product favored?

A)K_eq = 0.025
B)K_eq = 5.2
C)K_eq = 8.4 x 10^-5
D)K_eq = 6.3 x 10⁵
E)not enough information

Question 31

Given that the following reaction is exothermic, which of the following sets of changes would cause the following system at equilibrium to shift to increase the number of N₂O₄(g) molecules? 2NO₂(g) ⇌N₂O₄(g) What observation would indicate that the reaction is at equilibrium in a closed container?

A)Increasing container volume and increasing temperature
B)Increasing container volume and decreasing temperature
C)Decreasing container volume and increasing temperature
D)Decreasing container volume and decreasing temperature
E)Changing volume or temperature will not affect the number of gas molecules present at equilibrium

Question 32

Consider the following reaction carried out in a sealed container: N₂(g) + 3H₂(g) ⇌ 2NH₃(g) A state of equilibrium cannot be reached if the container initially contains

A)NH₃ only.
B)N₂ only.
C)NH₃ and N₂ only.
D)NH₃, N_2, and H₂.

Question 33

Select the correct equilibrium constant expression for the following reaction: H₂(g) + I₂(g) ⇌ 2HI(g)

A)
B)K_eq = [HI]² [H₂][I₂]
C)K_eq = [HI]² + [H₂] + [I₂]
D)
E)

Question 34

Select the correct equilibrium constant expression for the reaction 4NH₃(g) + 3O₂(g) ⇌ 2N₂(g) + 6H₂O(g)

A)
B)
C)
D)
E)

Question 35

In order to write the equilibrium constant expression for a reaction, you must:

A)know the mechanism for the reaction.
B)know the rate of the forward and reverse reactions.
C)know the concentrations of all reactants and products.
D)have the balanced chemical equation for the reaction.
E)know the conditions of pressure, temperature, and concentration for the system.

Question 36

Select the correct equilibrium constant expression for the reaction: CH₄(g) + 2H₂S(g) ⇌ CS₂(g) + 4H₂(g)

A)
B)
C)
D)K_eq = [CS₂][H₂]⁴ - [CH₄][H₂S]²
E)K_eq = [CS₂][H₂]⁴ + [CH₄][H₂S]²

Question 37

For a given reaction, which of the following statements can be made about the value of the equilibrium constant?

A)It always remains the same.
B)It increases when the concentration of one of the products is increased.
C)It increases when the concentration of one of the reactants is increased.
D)It changes when temperature is changed.
E)It can be changed by addition of a catalyst.

Question 38

Consider the following reaction carried out in a sealed container: 2SO₃(g) ⇌ 2SO₂(g) + O₂(g) A state of equilibrium can be reached if the container initially contains

A)SO₃ only
B)SO₂ and O₂ only.
C)SO₃ and O₂ only.
D)SO₃, SO_2, and O₂.
E)any of these combinations of reactants and products.

Question 39

The high potential-energy chemical species that is produced when an effective collision occurs is called a catalyst.

Question 40

Consider the following reaction carried out in a sealed container: 2SO₃(g) ⇌ 2SO₂(g) + O₂(g) A state of equilibrium cannot be reached if the container initially contains

A)SO₃ only.
B)O₂ only.
C)SO₂ and O₂ only.
D)SO₃ and O₂ only.
E)SO_{3 ,} SO₂ and O₂.

Question 41

Catalysts are not included in an overall chemical reaction because they are regenerated during the reaction.

Question 42

When we say that the position of equilibrium lies to the left, it means that there are fewer reactants than products at equilibrium.

Question 43

A catalyst gives an alternate pathway for a reaction that has a lower activation energy.

Question 44

The reaction CaCO₃(s) CaO(s) + CO₂(g) is an example of a heterogeneous equilibrium.

Question 45

If heat is added to the system of an endothermic reaction, the equilibrium will shift to make more reactants.

Question 46

If the average energy of the products of a chemical reaction is greater than the average energy of the reactants, then the reaction is exothermic.

Question 47

The enzyme sucrase catalyzes the metabolism of sucrose.

Question 48

The only condition which can cause the equilibrium constant for a specific reaction to change is a temperature change.

Question 49

An activated complex is a short-lived, high-energy species that is formed during the process of a chemical reaction.

Question 50

A catalyst increases the rate of a reaction by increasing the kinetic energy of the reactants.

Question 51

An intermediate in a chemical reaction is a species that the reactant molecules interact with during an early step in a reaction that is regenerated during a later step in the reaction.

Question 52

When square brackets are placed around the formula for a substance in an equilibrium constant expression, it indicates the percent-by-mass concentration of that substance.For example [NaOH] means the percent-by-mass concentration of NaOH.