Chemical Equilibrium: Interactive Quizzes and Learning Resources

Question 1

According to Le Chatelier's principle, which change in conditions will shift the equilibrium to the right (favour products) for an endothermic reaction?

Accepted Answer

Increasing temperature

Answer

Decreasing temperature

Answer

Increasing pressure (for gaseous reactants/products)

Answer

Decreasing volume (for gaseous reactants/products)

Question 2

The equilibrium constant expression for the reaction A + B ⇌ 2C is:

Accepted Answer

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

Answer

[A][B]

Answer

[C]

Question 3

According to Le Chatelier's principle, which of the following changes will shift the equilibrium of the reaction N2(g) + 3H2(g) ⇌ 2NH3(g) to the left?

Accepted Answer

Increasing the concentration of N2

Answer

Increasing the pressure

Answer

Adding a catalyst

Question 4

Which of the following statements about weak acids is accurate?

Accepted Answer

They produce a low concentration of H+ ions in solution.

Answer

They ionize completely in water.

Answer

They have a high equilibrium constant for ionization.

Question 5

Which equation can be used to calculate the pH of a solution of a weak acid?

Accepted Answer

pH = pKa - log([A-] / [HA])

Answer

pH = -log[H+]

Answer

pH = pKa + log([A-] / [HA])

Question 6

The common ion effect refers to the:

Accepted Answer

Decrease in solubility of slightly soluble salts in the presence of a common ion

Answer

Increase in the rate of a reaction in the presence of a catalyst

Answer

Shift in equilibrium towards the formation of reactants

Question 7

An equilibrium reaction is given as N2 (g) + O2 (g) <=> 2NO (g). According to Le Chatelier's principle, how will the equilibrium shift if the temperature is increased?

Accepted Answer

Towards the products

Answer

Towards the reactants

Question 8

According to Le Chatelier's principle, if the concentration of reactants in a reversible reaction is increased, what will happen to the equilibrium position?

Accepted Answer

Shift towards products

Answer

Shift towards reactants

Answer

No shift

Answer

Cannot be predicted

Question 9

For a reaction that proceeds to completion, what is the value of the equilibrium constant?

Accepted Answer

Infinity

Answer

0

Answer

1

Answer

Cannot be determined from the given information

Question 10

Consider the reaction: CaCO3(s) ⇌ CaO(s) + CO2(g). If the equilibrium mixture is heated, what will happen to the partial pressure of CO2?

Accepted Answer

Increase

Answer

Decrease

Answer

No change

Answer

Cannot be determined from the given information

Question 11

Which of the following conditions indicates that a chemical reaction has reached equilibrium?

Accepted Answer

The concentrations of the reactants and products remain constant

Answer

The forward reaction rate is greater than the reverse reaction rate

Answer

The enthalpy change of the reaction is zero

Answer

The Gibbs free energy change of the reaction is negative

Question 12

An equilibrium constant has a value of 0.5. What does this value signify?

Accepted Answer

The reaction favours the formation of reactants

Answer

The reaction favours the formation of products

Answer

The reaction is at equilibrium

Answer

The reaction is spontaneous

Question 13

A reaction has a high activation energy. How will this affect the rates of the forward and reverse reactions at equilibrium?

Accepted Answer

The rates of the forward and reverse reactions will be equal and non-zero

Answer

The rate of the forward reaction will be faster than the rate of the reverse reaction

Answer

The rate of the reverse reaction will be faster than the rate of the forward reaction

Answer

The rates of the forward and reverse reactions will be zero

Question 14

What is the significance of the Gibbs free energy change in chemical equilibrium?

Accepted Answer

It determines the direction of the reaction

Answer

It determines the equilibrium constant

Answer

It determines the rate of the reaction

Answer

It determines the activation energy of the reaction

Question 15

Which of the following expressions represents the equilibrium constant (K) for the reaction A + B ⇌ C?

Accepted Answer

K = [A][B]/[C]

Answer

K = [C]/[A][B]

Answer

K = 1/[C]

Answer

K = [A]/[B]

Question 16

Which of the following statements about the equilibrium constant is correct?

Accepted Answer

It is a dimensionless quantity.

Answer

It is independent of temperature.

Answer

It is always greater than 1.

Answer

It is affected by the initial concentrations of reactants and products.

Question 17

Consider the following reaction at equilibrium: CO(g) + H2O(g) ⇌ CO2(g) + H2(g). If the concentration of CO is increased, which of the following will occur?

Accepted Answer

The equilibrium will shift to the right.

Answer

The equilibrium will shift to the left.

Answer

The equilibrium will not shift.

Answer

The equilibrium constant will increase.

Question 18

Which of the following reactions has a large equilibrium constant?

Accepted Answer

N2(g) + 3H2(g) ⇌ 2NH3(g)

Answer

CO2(g) + H2(g) ⇌ CO(g) + H2O(g)

Answer

CH4(g) + 2O2(g) ⇌ CO2(g) + 2H2O(g)

Answer

H2O(l) ⇌ H+(aq) + OH-(aq)

Question 19

According to Le Chatelier's principle, which change will shift the equilibrium of the reaction: N2(g) + 3H2(g) <=> 2NH3(g) to the right?

Accepted Answer

Increasing the temperature

Answer

Decreasing the pressure

Answer

Adding more N2

Answer

Adding a catalyst

Question 20

At equilibrium, the equilibrium constant for a reaction is:

Accepted Answer

Equal to the ratio of the rate constants of the forward and reverse reactions

Answer

Zero

Answer

A very large number

Answer

A very small number

Question 21

An example of a heterogeneous equilibrium is:

Accepted Answer

Decomposition of solid CaCO3

Answer

Dissolution of CO2 in water

Answer

Reaction of hydrogen and oxygen gases

Answer

Dissociation of water into hydrogen and oxygen ions

Question 22

Classify the following reaction as homogeneous or heterogeneous:

Fe(s) + Cu2+(aq) <=> Fe2+(aq) + Cu(s)

Accepted Answer

Heterogeneous

Answer

Homogeneous

Question 23

Consider the reaction N2(g) + 3H2(g) ⇌ 2NH3(g). What happens to the equilibrium when the pressure is increased by decreasing the volume?

Accepted Answer

Shifts right

Answer

Shifts left

Answer

Does not shift

Answer

Forward reaction rate increases, but reverse reaction rate remains the same

Question 24

Consider the reaction 2NO(g) + O2(g) ⇌ 2NO2(g). What happens when more NO is added to the system at equilibrium?

Accepted Answer

Concentration of NO2 increases

Answer

Concentration of NO2 decreases

Answer

Concentration of NO2 remains the same

Answer

Reaction proceeds in the reverse direction, forming more NO

Question 25

Which reaction has the largest equilibrium constant?

Accepted Answer

K = 10^3

Answer

K = 10^-3

Answer

K = 10

Answer

K = 0.1

Question 26

Which of the following is a weak acid?

Accepted Answer

CH3COOH

Answer

HCl

Answer

HNO3

Answer

H2SO4

Question 27

Which of the following expressions represents the equilibrium constant, Kc, for the reaction: aA + bB <=> cC + dD?

Accepted Answer

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

Answer

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

Answer

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

Answer

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

Question 28

According to Le Chatelier's principle, what will happen to the concentration of B when more reactant A is added to the equilibrium system: aA <=> bB?

Accepted Answer

The concentration of B will increase.

Answer

The concentration of B will decrease.

Answer

The concentration of B will remain the same.

Answer

The reaction will proceed in the reverse direction.

Question 29

What is the main difference between a homogeneous and a heterogeneous equilibrium?

Accepted Answer

Homogeneous equilibria occur in a single phase, while heterogeneous equilibria occur in multiple phases.

Answer

Homogeneous equilibria involve only gases, while heterogeneous equilibria involve solids or liquids.

Answer

Homogeneous equilibria are always spontaneous, while heterogeneous equilibria are not.

Answer

There is no difference between homogeneous and heterogeneous equilibria.

Question 30

For the reaction: A(g) + B(g) <=> C(g), which expression represents the equilibrium constant, K?

Accepted Answer

K = [A][B]/[C]

Answer

K = [C]/[A][B]

Answer

K = [A][C]/[B]

Answer

K = [B][C]/[A]

Question 31

Which factor has no effect on the equilibrium position of a reaction?

Accepted Answer

Addition of a catalyst

Answer

Change in temperature

Answer

Change in reactant concentration

Answer

Volume of the reaction vessel

Question 32

Which reaction is exothermic?

Accepted Answer

A(g) + B(g) <=> C(g) + heat

Answer

D(g) <=> E(g) - heat

Answer

F(g) + G(g) <=> H(g)

Answer

I(g) <=> J(g) + heat

Question 33

In the reaction: Ag+(aq) + Cl-(aq) <=> AgCl(s), which ion is a spectator ion?

Accepted Answer

Cl-

Answer

Ag+

Answer

AgCl

Answer

H+

Question 34

At equilibrium, what is the relationship between the rates of the forward and reverse reactions?

Accepted Answer

Equal

Answer

Zero

Answer

Greater than one

Answer

Less than one

Question 35

What is the effect of adding a catalyst on a chemical reaction that has reached equilibrium?

Accepted Answer

It does not affect the equilibrium position.

Answer

It shifts the equilibrium to the left.

Answer

It shifts the equilibrium to the right.

Answer

It increases the rate of the forward reaction only.

Question 36

Which of the following is NOT a condition for chemical equilibrium?

Accepted Answer

The reactants and products can be easily separated

Answer

The forward and reverse reactions occur at equal rates

Answer

The concentrations of the reactants and products remain constant over time

Answer

The temperature of the system remains constant

Question 37

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

Accepted Answer

Presence of a catalyst

Answer

Temperature

Answer

Pressure

Answer

Concentration of the reactants

Question 38

How is the equilibrium constant (K) related to the rate constants of the forward (kf) and reverse (kr) reactions?

Accepted Answer

K = kf / kr

Answer

K = kf - kr

Answer

K = kr / kf

Answer

K = kf + kr

Question 39

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

Accepted Answer

2H2(g) + O2(g) <=> 2H2O(g)

Answer

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

Answer

Fe(s) + 2HCl(aq) <=> FeCl2(aq) + H2(g)

Answer

Ag+(aq) + Cl-(aq) <=> AgCl(s)

Question 40

Which of the following variables does not influence the equilibrium position of a reversible reaction?

Accepted Answer

Duration of the reaction

Answer

Concentrations of reactants

Answer

Concentrations of products

Answer

Temperature

Question 41

Which statement accurately describes an equilibrium reaction?

Accepted Answer

The concentrations of reactants and products remain constant over time

Answer

The forward and reverse reactions cease entirely

Answer

The forward reaction proceeds until all reactants are consumed

Answer

The reverse reaction proceeds until all products are consumed

Question 42

Which characteristic is typical of a strong electrolyte?

Accepted Answer

Complete dissociation in solution

Answer

Possession of a weak conjugate base or acid

Answer

A low equilibrium constant value

Answer

Nonpolar molecular structure

Question 43

Which of the following acids is the strongest?

Accepted Answer

Hydrochloric acid (HCl)

Answer

Acetic acid (CH3COOH)

Answer

Carbonic acid (H2CO3)

Answer

Ammonium hydroxide (NH4OH)

Question 44

According to Le Chatelier's principle, if the concentration of reactants is increased, the equilibrium will shift:

Accepted Answer

To the right

Answer

To the left

Answer

Not at all

Answer

In the direction that consumes reactants

Question 45

Which equilibrium is homogeneous?

Accepted Answer

2NO2(g) ⇌ N2O4(g)

Answer

CaCO3(s) ⇌ CaO(s) + CO2(g)

Answer

Fe(s) + 2HCl(aq) ⇌ FeCl2(aq) + H2(g)

Answer

AgCl(s) + 2NH3(aq) ⇌ [Ag(NH3)2]+(aq) + Cl-(aq)

Question 46

What is true about the Gibbs free energy change (ΔG) in a chemical equilibrium?

Accepted Answer

ΔG = 0

Answer

ΔG is always negative

Answer

ΔG is always positive

Answer

ΔG can be positive or negative depending on the reaction

Question 47

The equilibrium constant for the reaction 2A ⇌ B is 4. What is the equilibrium constant for the reverse reaction B ⇌ 2A?

Accepted Answer

0.25

Answer

0.5

Answer

1

Answer

4

Question 48

What is the fundamental concept of chemical equilibrium?

Accepted Answer

Forward and reverse reactions proceed at the same rate

Answer

Reactants are consumed faster than products are formed

Answer

Concentrations of reactants and products continuously change

Answer

The equilibrium constant remains constant over time

Question 49

Which factor has no influence on the equilibrium constant?

Accepted Answer

Volume of the reaction container

Answer

Temperature

Answer

Concentration of reactants and products

Answer

Nature of reactants and products

Question 50

What is the primary purpose of Le Chatelier's principle?

Accepted Answer

Predicting the direction of a reaction shift

Answer

Calculating the equilibrium constant

Answer

Determining the rate of a reaction

Answer

Measuring the concentration of reactants and products

Question 51

If the concentration of a reactant increases, what will happen to the equilibrium position?

Accepted Answer

Shift to the right (favoring products)

Answer

Shift to the left (favoring reactants)

Answer

Remain unchanged

Answer

Cannot be determined without more information

Question 52

Which change will not alter the equilibrium position?

Accepted Answer

Adding a catalyst

Answer

Increasing temperature

Answer

Decreasing volume

Answer

Removing a product

Question 53

Which attribute characterizes an equilibrium reaction?

Accepted Answer

Forward and reverse reactions occur at equal rates

Answer

Concentrations of reactants and products continuously change

Answer

The equilibrium constant is always greater than 1

Answer

The reaction is irreversible

Question 54

What does a large equilibrium constant value suggest?

Accepted Answer

The reaction favors the products

Answer

The reaction favors the reactants

Answer

The reaction is balanced

Answer

The reaction is slow

Question 55

According to Le Chatelier's principle, how will the equilibrium of a reversible reaction shift if the concentration of reactants is increased?

Accepted Answer

Towards products

Answer

Towards reactants

Answer

Neither towards reactants nor products

Answer

It is impossible to predict

Question 56

Which of the following factors does not affect the equilibrium constant of a reaction?

Accepted Answer

Identity of the reactants

Answer

Temperature

Answer

Pressure

Answer

Concentration of reactants

Question 57

Which reaction will have the smallest equilibrium constant?

Accepted Answer

K = 0.01

Answer

K = 1

Answer

K = 0.1

Answer

K = 100

Question 58

Consider the reaction: CaCO3(s) <=> CaO(s) + CO2(g). Which of the following changes will cause the equilibrium to shift to the right?

Accepted Answer

Increasing the temperature

Answer

Decreasing the volume

Answer

Adding CaCO3 to the system

Answer

Removing CO2 from the system

Question 59

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

Accepted Answer

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

Answer

2NO2(g) <=> N2O4(g)

Answer

H2O(l) <=> H2O(g)

Answer

NaOH(aq) + HCl(aq) <=> NaCl(aq) + H2O(l)

Question 60

Consider the equilibrium reaction: A + B <=> C + D. What happens to the concentration of C if the concentration of A is increased?

Accepted Answer

The concentration of C increases

Answer

The concentration of D increases

Answer

The concentrations of both C and D increase

Answer

Neither the concentration of C nor D changes

Question 61

Which statement about catalysts is accurate?

Accepted Answer

Catalysts accelerate the attainment of equilibrium

Answer

Catalysts increase the equilibrium constant of a reaction

Answer

Catalysts alter the equilibrium position

Answer

Catalysts are consumed in the course of a reaction

Question 62

Which of the following reactions is NOT a homogeneous equilibrium?

Accepted Answer

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

Answer

2NO(g) <=> N2(g) + O2(g)

Answer

CO(g) + H2O(g) <=> CO2(g) + H2(g)

Answer

CH3COOH(aq) <=> H+(aq) + CH3COO-(aq)

Question 63

Consider the equilibrium: CO(g) + Cl2(g) ⇌ COCl2(g) + heat. Which action will increase COCl2(g) yield?

Accepted Answer

Raising temperature

Answer

Lowering pressure

Answer

Adding an inert gas

Answer

Adding a catalyst

Question 64

Which reaction has a negative equilibrium constant?

Accepted Answer

CO2(g) + H2(g) ⇌ CO(g) + H2O(g)

Answer

2H2(g) + O2(g) ⇌ 2H2O(g)

Answer

N2(g) + 3H2(g) ⇌ 2NH3(g)

Answer

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