Chemical Equilibrium: Understanding the Dynamics of Reversible Reactions

Question 1

For the reaction: 2SO2(g) + O2(g) <=> 2SO3(g) + heat, what happens if the temperature is increased?

Accepted Answer

Equilibrium shifts to the right (favoring SO3)

Answer

Equilibrium shifts to the left (favoring SO2)

Answer

Equilibrium constant increases

Answer

Equilibrium constant decreases

Question 2

For the equilibrium reaction aA + bB ⇌ cC + dD, what is the expression for the equilibrium constant, Kc?

Accepted Answer

Kc = [C]^c[D]^d / [A]^a[B]^b

Answer

Kc = [A]^a[B]^b / [C]^c[D]^d

Answer

Kc = (aA + bB) / (cC + dD)

Answer

Kc = (cC + dD) / (aA + bB)

Question 3

Which of the following factors does NOT affect the value of the equilibrium constant?

Accepted Answer

Surface area of the reactants

Answer

Temperature

Answer

Concentration of reactants and products

Answer

Presence of a catalyst

Question 4

The Haber process for the production of ammonia is an industrial application of equilibrium principles. What are the optimal conditions for maximizing the yield of ammonia?

Accepted Answer

Low temperature and high pressure

Answer

High temperature and low pressure

Answer

High pressure and high temperature

Answer

Low pressure and low temperature

Question 5

What is the conjugate acid of NH3?

Accepted Answer

NH4+

Answer

NH2-

Answer

H3O+

Answer

OH-

Question 6

Which of the following salts will undergo hydrolysis in water to produce an acidic solution?

Accepted Answer

Ammonium chloride

Answer

Sodium acetate

Answer

Potassium nitrate

Answer

Sodium hydroxide

Question 7

Which of the following is NOT a characteristic of a catalyst?

Accepted Answer

It is consumed in the reaction.

Answer

It increases the rate of the reaction.

Answer

It lowers the activation energy of the reaction.

Answer

It is specific for a particular reaction.

Question 8

Which of the following is an example of a homogeneous catalyst?

Accepted Answer

Sulfuric acid in the esterification of carboxylic acids

Answer

Nickel in the hydrogenation of alkenes

Answer

Platinum on carbon in catalytic converters

Answer

Copper in the Haber process

Question 9

Which of the following is a characteristic of a weak acid?

Accepted Answer

Produces a low concentration of hydrogen ions

Answer

Dissociates completely in water

Answer

Has a high equilibrium constant

Answer

Produces a high concentration of hydroxide ions

Question 10

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

Accepted Answer

Presence of a Catalyst

Answer

Concentration of reactants

Answer

Concentration of products

Answer

Temperature

Question 11

Which of the following reactions represents a heterogeneous equilibrium?

Accepted Answer

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

Answer

H2(g) + Cl2(g) <=> 2HCl(g)

Answer

2NH3(g) <=> N2(g) + 3H2(g)

Answer

CH3COOH(aq) + H2O(l) <=> CH3COO-(aq) + H3O+(aq)

Question 12

An equilibrium reaction has an equilibrium constant of 0.1. This indicates that:

Accepted Answer

The reaction proceeds more favorably in the reverse direction.

Answer

The reaction proceeds more favorably in the forward direction.

Answer

The forward and reverse reactions occur at equal rates.

Answer

The reaction has reached completion.

Question 13

Which of the following factors will shift the equilibrium of a reaction to the left according to Le Chatelier's principle?

Accepted Answer

Removing a product

Answer

Increasing temperature

Answer

Increasing pressure

Answer

Adding a catalyst

Question 14

Identify the predominant species in a solution of sodium hydrogen carbonate (NaHCO3).

Accepted Answer

HCO3-

Answer

H2CO3

Answer

CO32-

Answer

OH-

Question 15

Which of the following statements about chemical equilibrium is accurate?

Accepted Answer

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

Answer

Equilibrium is a static state where no net change occurs.

Answer

Equilibrium can only be achieved in closed systems.

Answer

Equilibrium is an irreversible process.

Question 16

Consider the reaction: Fe3+(aq) + SCN-(aq) <=> FeSCN2+(aq). Which ion will cause an increase in the concentration of FeSCN2+ at equilibrium?

Accepted Answer

SCN-

Answer

Fe3+

Answer

H+

Answer

OH-

Question 17

Which of the following is a property of a strong acid?

Accepted Answer

Has a large equilibrium constant

Answer

Partially ionizes in water

Answer

Is a weak electrolyte

Answer

Produces few H+ ions in solution

Question 18

What is the primary purpose of using a buffer solution?

Accepted Answer

To maintain a relatively constant pH even upon dilution or the addition of small amounts of acid or base

Answer

To increase the rate of a reaction

Answer

To decrease the equilibrium constant of a reaction

Answer

To act as a solvent for chemical reactions

Question 19

Which of the following is a characteristic of a system in chemical equilibrium?

Accepted Answer

The concentrations of reactants and products remain constant over time.

Answer

The Gibbs free energy of the system is maximized.

Answer

The forward and reverse reactions cease to occur.

Answer

Equilibrium is achieved only in closed systems.

Question 20

The reaction 2NO2(g) <=> N2O4(g) is exothermic. In which direction will the equilibrium shift if the temperature is lowered?

Accepted Answer

Left (towards reactants)

Answer

Right (towards products)

Answer

No shift

Answer

Cannot be determined

Question 21

For a reversible reaction at equilibrium, what is true about the rates of the forward and reverse reactions?

Accepted Answer

The forward and reverse reaction rates are equal.

Answer

The reverse reaction rate is higher than the forward reaction rate.

Answer

The forward reaction rate is higher than the reverse reaction rate.

Question 22

Consider the exothermic reaction: N2(g) + 3H2(g) ⇌ 2NH3(g). How will increasing the pressure affect the equilibrium position?

Accepted Answer

Shift to the right, favoring ammonia production.

Answer

Shift to the left, favoring nitrogen and hydrogen.

Answer

Only the value of Kc will increase.

Answer

No change in the equilibrium position.

Question 23

The reaction 2SO2(g) + O2(g) ⇌ 2SO3(g) is at equilibrium. What happens to the amount of SO3(g) if more O2(g) is added to the system?

Accepted Answer

The amount of SO3(g) will increase.

Answer

The amount of SO3(g) will remain the same.

Answer

The amount of SO3(g) will decrease.

Answer

The equilibrium constant, Kc, will increase.

Question 24

The equilibrium constant, Kc, for the reaction H2(g) + I2(g) ⇌ 2HI(g) is 50. What is the value of Kc for the reverse reaction, HI(g) ⇌ 1/2 H2(g) + 1/2 I2(g)?

Accepted Answer

0.020

Answer

-50

Answer

25

Answer

0.14

Question 25

The system at equilibrium is: A(g) + B(g) ⇌ 2C(g). If the concentration of A is increased, what will happen to the concentration of B?

Accepted Answer

Decrease

Answer

It depends on the initial concentration of C.

Answer

Increase

Answer

Remain the same

Question 26

A catalyst is added to a system already at equilibrium. What is the effect of the catalyst?

Accepted Answer

Increases the rate of both forward and reverse reactions equally.

Answer

Increases only the forward reaction rate.

Answer

Shifts the equilibrium position towards the products.

Answer

Increases only the reverse reaction rate.

Question 27

The reaction A(g) + B(g) ⇌ C(g) + D(g) has an equilibrium constant of 1.0. What does this tell us about the concentrations of reactants and products at equilibrium?

Accepted Answer

The concentrations of reactants and products are equal.

Answer

The forward reaction rate is higher than the reverse reaction rate.

Answer

The concentrations of reactants are higher than the products.

Answer

The concentrations of products are higher than the reactants.

Question 28

Consider the following equilibrium:  N₂(g) + 3H₂(g) ⇌ 2NH₃(g).  If the equilibrium constant (K) for this reaction is 6.0 at a certain temperature, what is the value of K for the reverse reaction?

Accepted Answer

0.17

Answer

12.0

Answer

6.0

Answer

36.0

Question 29

The reaction between hydrogen and iodine to form hydrogen iodide is reversible. Which of the following statements is TRUE about this reaction at equilibrium?

Accepted Answer

The forward and reverse reactions occur at equal rates.

Answer

The net reaction has stopped completely.

Answer

The concentrations of reactants and products are equal.

Question 30

The reaction between carbon dioxide and water to form carbonic acid is an equilibrium process. What would happen to the equilibrium if the concentration of carbon dioxide is increased?

Accepted Answer

The equilibrium would shift to the right, favoring the formation of more carbonic acid.

Answer

The equilibrium would not change.

Answer

The equilibrium would shift to the left, favoring the formation of more carbon dioxide and water.

Answer

The equilibrium constant (K) would increase.

Question 31

The following reaction is at equilibrium:  2SO₂(g) + O₂(g) ⇌ 2SO₃(g).  What would happen to the equilibrium if more oxygen (O₂) is added to the system?

Accepted Answer

The equilibrium would shift to the right, favoring the formation of more sulfur trioxide (SO₃).

Answer

The equilibrium position would not change.

Answer

The equilibrium would shift to the left, favoring the formation of more sulfur dioxide (SO₂).

Question 32

The equilibrium constant (K) for the reaction N₂(g) + 3H₂(g) ⇌ 2NH₃(g) is 0.10 at a certain temperature.  Which of the following statements is TRUE?

Accepted Answer

At equilibrium, the reactants are favored over the products.

Answer

At equilibrium, the products are favored over the reactants.

Answer

The concentrations of reactants and products are equal at equilibrium.

Answer

The reaction is irreversible.

Question 33

The following reaction is at equilibrium:  H₂(g) + I₂(g) ⇌ 2HI(g).  According to Le Chatelier's principle, what would happen to the equilibrium position if the volume of the container is decreased while maintaining a constant temperature?

Accepted Answer

The equilibrium would shift to the side with fewer moles of gas.

Answer

The equilibrium would shift to the side with more moles of gas.

Answer

The equilibrium constant (K) would increase.

Answer

The equilibrium position would not change.

Question 34

Which of the following factors does NOT affect the position of equilibrium?

Accepted Answer

The addition of a catalyst

Answer

Temperature

Answer

Pressure

Answer

Concentration

Question 35

Which of the following is the equilibrium constant expression for the reaction: N₂ + 3H₂ ⇌ 2NH₃?

Accepted Answer

Kp = (P(NH₃)²)/(P(N₂) * P(H₂)²)

Answer

Kc = (P(N₂) * P(H₂)³)/(P(NH₃)²)

Answer

Kc = (P(N₂) * P(H₂))/(P(NH₃)²)

Answer

Kp = (P(NH₃)²)/(P(N₂) * P(H₂)³)

Question 36

What is the relationship between the equilibrium constant and the position of equilibrium?

Accepted Answer

A higher equilibrium constant indicates a greater proportion of products.

Answer

The equilibrium constant is independent of the reaction conditions.

Answer

A higher equilibrium constant indicates a greater proportion of reactants.

Question 37

Which of the following changes would shift the equilibrium of the reaction: C(s) + H₂O(g) ⇌ CO(g) + H₂(g) to the right?

Accepted Answer

Increasing the temperature

Answer

Increasing the pressure

Answer

Decreasing the volume

Answer

Adding more H₂O(g)

Question 38

What is the effect of adding a catalyst on the equilibrium position of a reaction?

Accepted Answer

It does not affect the equilibrium position.

Answer

It increases the equilibrium constant.

Answer

It shifts the equilibrium to the side with more products.

Answer

It shifts the equilibrium to the side with more reactants.

Question 39

Which of the following is a homogeneous equilibrium?

Accepted Answer

CO(g) + Cl₂(g) ⇌ COCl₂(g)

Answer

C(s) + H₂O(g) ⇌ CO(g) + H₂(g)

Answer

CaCO₃(s) ⇌ CaO(s) + CO₂(g)

Answer

AgCl(s) ⇌ Ag⁺(aq) + Cl⁻(aq)

Question 40

What is the standard state for gaseous species in equilibrium constant expressions?

Accepted Answer

1 atm partial pressure

Answer

100 kPa partial pressure

Answer

1 M concentration

Answer

25 °C temperature

Question 41

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

Accepted Answer

Volume

Answer

Concentration of reactants and products

Answer

Temperature

Answer

Pressure

Question 42

What is the conjugate acid of NH₃?

Accepted Answer

NH₄⁺

Answer

OH⁻

Answer

H₃O⁺

Answer

H₂O

Question 43

Which of the following is a weak acid?

Accepted Answer

CH₃COOH

Answer

HCl

Answer

NaOH

Answer

H₂SO₄

Question 44

What is the pH of a 0.1 M solution of a monoprotic weak acid with a Ka of 1 x 10⁻⁵?

Accepted Answer

5

Answer

7

Answer

9

Answer

3