Chemical Equilibrium: Understanding the Balance of Reactions

Question 1

The equilibrium constant expression for the reaction A + B ⇌ C is:

Accepted Answer

[(C)] / [(A)][(B)]

Answer

(C) / (A) (B)

Answer

(A) (B) / (C)

Answer

[(A)][(B)] / [(C)]

Question 2

Which of the following reactions has the largest equilibrium constant?

Accepted Answer

D + E ⇌ F, Kc = 100

Answer

A + B ⇌ C, Kc = 10

Answer

G + H ⇌ I, Kc = 0.1

Answer

J + K ⇌ L, Kc = 0.01

Question 3

A solution of hydrogen chloride (HCl) has a pH of 1. What is the molar concentration of hydrogen ions (H+) in the solution?

Accepted Answer

10^-1 M

Answer

10^-7 M

Answer

10^-14 M

Answer

10^-10 M

Question 4

What is the conjugate base of the weak acid HF?

Accepted Answer

F-

Answer

H+

Answer

OH-

Answer

HF2-

Question 5

Which of the following expressions represents the equilibrium constant expression for the heterogeneous equilibrium: CaCO3(s) <=> CaO(s) + CO2(g)?

Accepted Answer

Kp = (P(CO2))

Answer

Kc = [CaO][CO2]

Answer

Kw = [H+][OH-]

Answer

Keq = [CaO][CO2]

Question 6

In a closed container, which of the following changes will not affect the equilibrium position of a gas-phase reaction?

Accepted Answer

Adding a catalyst to the container

Answer

Increasing the volume of the container

Answer

Adding a non-reactive gas into the container

Answer

Removing a product from the container

Question 7

Which of the following is the equilibrium constant expression for the reaction: 2NO2(g) ⇌ N2O4(g)?

Accepted Answer

Kp = [NO2]^2/[N2O4]

Answer

Kp = [NO2]/[N2O4]

Answer

Kp = [N2O4]/[NO2]^2

Answer

Kp = [N2O4]^2/[NO2]

Question 8

Which of the following factors does NOT affect the equilibrium position of a chemical reaction?

Accepted Answer

Addition of a catalyst

Answer

Concentration of reactants and products

Answer

Temperature

Answer

Pressure

Question 9

Consider the equilibrium: NH3(g) + HCl(g) ⇌ NH4Cl(s). What will happen to the equilibrium position if the volume of the container is decreased?

Accepted Answer

Shift to the left (favour reactants)

Answer

No change

Question 10

Which of the following is a characteristic of the common ion effect?

Accepted Answer

The solubility of a precipitate decreases when a common ion is added.

Answer

The rate of a reaction increases when a common ion is added.

Answer

The pH of a solution decreases when a common ion is added.

Answer

The boiling point of a solution increases when a common ion is added.

Question 11

Which of the following is an example of a heterogeneous equilibrium?

Accepted Answer

CaCO3(s) ⇌ CaO(s) + CO2(g)

Answer

CO(g) + 2H2(g) ⇌ CH3OH(g)

Answer

2NO2(g) ⇌ N2O4(g)

Answer

CH3COOH(aq) + H2O(l) ⇌ CH3COO-(aq) + H3O+(aq)

Question 12

What is the conjugate acid of NH3?

Accepted Answer

NH4+

Answer

NH2-

Answer

N3-

Answer

H3N

Question 13

Which of the following is NOT a factor that can shift the position of equilibrium?

Accepted Answer

Addition of a catalyst

Answer

Change in temperature

Answer

Change in pressure

Answer

Change in the volume of the system

Question 14

The equilibrium constant for a reaction is 4. What is the ratio of products to reactants at equilibrium?

Accepted Answer

4:1

Answer

1:4

Answer

1:2

Answer

2:1

Question 15

Which of the following reactions will shift to the right when the temperature is increased?

Accepted Answer

Endothermic reaction

Answer

Exothermic reaction

Answer

Reaction with no heat change

Answer

Reaction with a negative equilibrium constant

Question 16

What is the value of the equilibrium constant for a reaction that proceeds to completion?

Accepted Answer

Infinity

Answer

0

Answer

1

Answer

Cannot be determined

Question 17

Which of the following statements about equilibrium is true?

Accepted Answer

Equilibrium is a dynamic state where opposing reactions occur at equal rates.

Answer

Equilibrium is a static state where no change occurs.

Answer

Equilibrium is only achieved in closed systems.

Answer

Equilibrium is not affected by changes in temperature and pressure.

Question 18

Identify the heterogeneous reaction among the following:

Accepted Answer

CaCO3(s) <=> CaO(s) + CO2(g)

Answer

2HI(g) <=> H2(g) + I2(g)

Answer

CH3COOH(aq) + NaOH(aq) <=> CH3COONa(aq) + H2O(l)

Answer

2NO(g) + O2(g) <=> 2NO2(g)

Question 19

Consider the exothermic reaction: NH3(g) + HCl(g) <=> NH4Cl(s). How will the equilibrium shift if the temperature is raised?

Accepted Answer

To the left

Answer

To the right

Answer

No change

Answer

Cannot be determined

Question 20

Which expression accurately represents the equilibrium constant (Kc) for a given reaction?

Accepted Answer

Kc = [products]/[reactants]

Answer

Kp = [products]/[reactants]

Answer

Keq = [products] - [reactants]

Answer

Kd = [reactants]/[products]

Question 21

According to Le Chatelier's principle, which action would increase the yield of a desired product in a reversible reaction?

Accepted Answer

Removing products as they are formed

Answer

Decreasing the temperature

Answer

Increasing the volume of the reaction vessel

Answer

Adding more reactants

Question 22

Given a reaction with an equilibrium constant (Kc) of 2.5, what can be concluded?

Accepted Answer

The products are favored at equilibrium.

Answer

The reactants are favored at equilibrium.

Answer

The equilibrium concentrations of products and reactants are equal.

Answer

The reaction will proceed to completion.

Question 23

Consider the equilibrium: N2(g) + 3H2(g) ⇌ 2NH3(g). What is the effect of increasing pressure on this equilibrium?

Accepted Answer

The equilibrium will shift to the right.

Answer

The equilibrium will shift to the left.

Answer

The equilibrium will remain unchanged.

Answer

The reaction will proceed to completion.

Question 24

Which of the following changes will NOT affect the equilibrium position of a reaction?

Accepted Answer

Adding an inert gas

Answer

Changing the temperature

Answer

Adding a catalyst

Answer

Removing a product

Question 25

What is the primary function of a catalyst in a reversible reaction?

Accepted Answer

It lowers the activation energy of the reaction.

Answer

It increases the activation energy of the reaction.

Answer

It changes the equilibrium constant of the reaction.

Answer

It alters the products of the reaction.

Question 26

What is the relationship between the equilibrium constant and the standard Gibbs free energy change for a reaction?

Accepted Answer

ΔG^0 = -RTlnK

Answer

K = e^(-ΔG^0/RT)

Answer

K = ΔG^0/RT

Answer

ΔG^0 = KRTln2

Question 27

Which of the following represents a closed system at equilibrium?

Accepted Answer

A reaction where the forward and reverse reactions occur at equal rates.

Answer

A reaction that is stopped.

Answer

A reaction where the products are removed as they are formed.

Answer

A reaction where the reactants are continuously added.

Question 28

According to Le Chatelier's principle, which factor will NOT affect the equilibrium position of a reaction?

Accepted Answer

Addition of a catalyst

Answer

Change in reactant concentration

Answer

Change in temperature

Answer

Change in volume (for gaseous reactions only)

Question 29

Which of the following statements about equilibrium is true?

Accepted Answer

Equilibrium is a dynamic process.

Answer

Equilibrium concentrations do not change over time.

Answer

Equilibrium is only achieved when the forward and reverse reactions stop.

Answer

Equilibrium is not affected by changes in temperature.

Question 30

Which of the following is a weak acid?

Accepted Answer

Acetic acid

Answer

Hydrochloric acid

Answer

Sulfuric acid

Answer

Nitric acid

Question 31

Which of the following is a buffer solution?

Accepted Answer

A mixture of a weak acid and its salt

Answer

A mixture of a strong acid and its salt

Answer

A mixture of a weak base and its salt

Answer

A mixture of a strong base and its salt

Question 32

Which of the following best describes the state of chemical equilibrium?

Accepted Answer

Forward and reverse reactions occur at equal rates with no change in the concentrations of reactants or products over time

Answer

A reaction that proceeds exclusively in one direction until one of the reactants is entirely consumed

Answer

A reaction where the equilibrium constant is very large, indicating a strong preference for the formation of products

Answer

A reaction that is irreversible and cannot be reversed under any conditions

Question 33

What characteristic is typical of a strong acid?

Accepted Answer

High degree of ionization in water

Answer

Low pH

Answer

High pKa

Answer

Weak electrolyte

Question 34

A solution has a hydrogen ion concentration of 2.5 × 10^-4 M. What is the pH of this solution?

Accepted Answer

3.60

Answer

4.00

Answer

7.00

Answer

10.40

Question 35

Which of the following solutions can act as a buffer?

Accepted Answer

A solution containing a weak acid and its salt

Answer

A solution containing a strong acid and a strong base

Answer

A solution containing a weak base

Answer

A solution containing only water

Question 36

What is the primary purpose of a titration experiment?

Accepted Answer

To determine the concentration of an unknown solution

Answer

To neutralize an acid and a base completely

Answer

To measure the pH of a solution

Answer

To separate two different solutions

Question 37

Which of the following is NOT a factor that can influence the equilibrium position of a chemical reaction?

Accepted Answer

Surface area of reactants

Answer

Temperature

Answer

Concentration of reactants

Answer

Presence of a catalyst

Question 38

An equilibrium constant (Kc) greater than 1 indicates that:

Accepted Answer

The reaction favors the products.

Answer

The reaction favors the reactants.

Answer

The forward and reverse reactions occur at equal rates.

Answer

The concentration of reactants is higher than products.

Question 39

What is the relationship between the reaction quotient (Q) and the equilibrium constant (Kc)?

Accepted Answer

Q = Kc when the reaction is at equilibrium.

Answer

Q < Kc when the reaction favors the reactants.

Answer

Q > Kc when the reaction favors the products.

Answer

Q is always equal to Kc, regardless of the reaction conditions.

Question 40

What is the approximate pH of a 0.01 mol/L solution of a strong acid?

Accepted Answer

1

Answer

2

Answer

7

Answer

10

Question 41

What is the role of an indicator in a titration?

Accepted Answer

To provide a visual signal of the endpoint

Answer

To neutralize the solution

Answer

To determine the equivalence point

Answer

To speed up the reaction

Question 42

Which factor does NOT affect the equilibrium position of a reaction?

Accepted Answer

Chemical nature of the reactants

Answer

Temperature

Answer

Pressure

Answer

Concentration of reactants

Question 43

Identify a characteristic of a weak acid.

Accepted Answer

Low ionization constant

Answer

High equilibrium constant

Answer

Produces a large amount of H+ ions

Answer

Completely dissociates in water

Question 44

Consider the reaction: Fe3+(aq) + SCN-(aq) <=> FeSCN2+(aq). Adding which ion would shift the equilibrium to the right?

Accepted Answer

SCN-

Answer

Fe3+

Answer

Cl-

Answer

OH-

Question 45

Consider the reaction: 2SO2(g) + O2(g) <=> 2SO3(g). Describe the effect of adding a catalyst to the system on the equilibrium position.

Accepted Answer

Has no effect on the equilibrium position

Answer

Shifts the equilibrium to the left

Answer

Shifts the equilibrium to the right

Answer

Cannot be determined

Question 46

Which of the following reactions is at equilibrium?

Accepted Answer

Reaction rate of forward reaction is equal to the reaction rate of reverse reaction

Answer

Reaction rate of forward reaction is greater than the reaction rate of reverse reaction

Answer

Reaction rate of forward reaction is less than the reaction rate of reverse reaction

Answer

Reaction rate of forward reaction plus reaction rate of reverse reaction equals zero

Question 47

Consider the reaction: CO(g) + H2O(g) ⇌ CO2(g) + H2(g). If the equilibrium constant, K, is 10 at a particular temperature, what can you conclude?

Accepted Answer

Products are favored at equilibrium.

Answer

Reactants are favored at equilibrium.

Answer

The reaction is equally likely to proceed in both directions.

Answer

More information is needed to draw any conclusions.

Question 48

In a closed system, the equilibrium position of a reaction will shift to counteract any change that is made.

Accepted Answer

True

Answer

False

Question 49

Which expression represents the equilibrium constant, Kc, for the reaction: 2A + B ⇌ 3C?

Accepted Answer

[A]^2[B]/[C]^3

Answer

[C]^3/[A]^2[B]

Answer

[A]^2[B]/[C]^2

Answer

[C]^2/[A]^2[B]

Question 50

In a closed system at equilibrium, the concentrations of the reactants and products:

Accepted Answer

Remain constant indefinitely

Answer

Gradually change over time

Answer

Increase over time

Answer

Decrease over time

Question 51

The equilibrium constant for the reaction: N2(g) + 3H2(g) ⇌ 2NH3(g) is 0.1. If the initial concentrations of N2, H2, and NH3 are 1 M, which species is the limiting reactant?

Accepted Answer

N2

Answer

H2

Answer

NH3

Answer

The reaction will not reach equilibrium

Question 52

Which statement accurately describes heterogeneous equilibrium?

Accepted Answer

It involves at least one solid or liquid phase.

Answer

It involves only solid and liquid phases.

Answer

It involves only gas and liquid phases.

Answer

All phases are in the same physical state.

Question 53

Which of the following reactions is an example of homogeneous equilibrium?

Accepted Answer

2NO2(g) ⇌ N2O4(g)

Answer

CaCO3(s) ⇌ CaO(s) + CO2(g)

Answer

CH4(g) + 2O2(g) ⇌ CO2(g) + 2H2O(l)

Answer

Pb(s) + 2Ag+(aq) ⇌ Pb2+(aq) + 2Ag(s)

Question 54

The reaction: 2SO2(g) + O2(g) ⇌ 2SO3(g) is exothermic. Which change will shift the equilibrium to the left?

Accepted Answer

Increasing temperature

Answer

Decreasing pressure

Answer

Adding a catalyst

Answer

Removing SO2(g)