Chemical Equilibrium Quizzes: Test Your Understanding

Question 1

For the reaction: 2A(g) + B(g) <=> 3C(g), the equilibrium constant expression is Kc = [C]^3/[A]^2[B]. Explain how changing the initial concentration of B affects the value of Kc.

Accepted Answer

Changing the initial concentration of B shifts the equilibrium position, affecting the concentrations of all species and thus Kc.

Answer

The equilibrium constant is a constant and cannot be affected by changes in initial concentrations.

Answer

The equilibrium constant is only affected by changes in temperature.

Answer

Changing the initial concentration of B does not affect Kc because the equilibrium constant is determined by the reaction's stoichiometry.

Question 2

Given the equilibrium reaction: $$A(g) + B(g) ⇌ C(g)$$, if the equilibrium constant, Kc, exceeds the reaction quotient, Qc, what will happen?

Accepted Answer

The reaction will shift towards the products (C).

Answer

The reaction will shift towards the reactants (A and B).

Answer

The reaction will not proceed in either direction.

Answer

The value of Kc is not relevant in determining the reaction's direction.

Question 3

How do equilibrium principles contribute to understanding enzyme-catalyzed reactions in biochemistry?

Accepted Answer

Determining optimal pH and temperature for enzyme activity

Accepted Answer

Predicting the direction and extent of enzyme-catalyzed reactions

Answer

Enzyme-catalyzed reactions do not reach equilibrium

Answer

Equilibrium principles are irrelevant to enzyme-catalyzed reactions

Question 4

How does the presence of a catalyst affect the equilibrium constant, K, of a reaction? Select the correct answer and provide a brief explanation.

Accepted Answer

K remains unchanged because catalysts do not affect the relative concentrations of reactants and products at equilibrium.

Answer

K increases because catalysts increase the rate of the forward reaction only.

Answer

K decreases because catalysts decrease the activation energy of the backward reaction.

Answer

K increases because catalysts shift the equilibrium position towards the products.

Question 5

In the design and optimization of chemical reactors, how are equilibrium principles utilized to manipulate factors like temperature, pressure, and residence time?

Accepted Answer

By adjusting temperature, pressure, and residence time, the equilibrium position can be shifted towards the desired product, improving efficiency and yield.

Answer

Temperature, pressure, and residence time have no impact on equilibrium position and are thus irrelevant in reactor design.

Answer

The equilibrium position is fixed and remains unaffected by changes in temperature, pressure, or residence time.

Answer

Equilibrium principles are not applicable to industrial chemical reactors.

Question 6

According to Le Chatelier's principle, if a stress is applied to a system in equilibrium, the system will shift in a direction that:

Accepted Answer

Counteracts the stress

Answer

Exacerbates the stress

Answer

Remains unchanged

Answer

Predicts the equilibrium constant

Question 7

Consider the following reaction: N2(g) + 3H2(g) <=> 2NH3(g). Increasing the concentration of hydrogen gas (H2) to the system will:

Accepted Answer

Shift the equilibrium to the right

Answer

Shift the equilibrium to the left

Answer

Have no effect on the equilibrium

Answer

Decrease the rate of the forward reaction

Question 8

The equilibrium constant (Kc) for a reaction is a measure of:

Accepted Answer

The relative amounts of reactants and products at equilibrium

Answer

The extent to which the reaction proceeds

Answer

The rate at which the reaction occurs

Answer

The activation energy required for the reaction

Question 9

Which of the following reactions is favored at higher temperatures?

Accepted Answer

Endothermic reactions

Answer

Exothermic reactions

Answer

Neither exothermic nor endothermic reactions

Answer

All reactions

Question 10

Which of the following statements about chemical equilibrium is accurate?

Accepted Answer

Chemical equilibrium is a dynamic process where the forward and reverse reactions occur at equal rates.

Answer

At equilibrium, the concentrations of reactants and products remain unchanged.

Answer

Equilibrium is only achievable in closed systems.

Answer

Equilibrium is a static state where no further changes occur.

Question 11

According to Le Chatelier's principle, increasing the concentration of a reactant in a system at equilibrium will cause the equilibrium to shift:

Accepted Answer

Towards the product side

Answer

Towards the reactant side

Answer

Not at all

Answer

In an unpredictable direction

Question 12

Which of the following will NOT affect the equilibrium position of a gaseous system?

Accepted Answer

Addition of a catalyst

Answer

Change in temperature

Answer

Change in pressure

Answer

Change in volume

Question 13

Consider the following equilibrium: N2(g) + 3H2(g) <=> 2NH3(g) + heat. If the temperature is increased, the equilibrium will shift:

Accepted Answer

To the right

Answer

To the left

Answer

Not at all

Answer

In the direction of the heat-releasing reaction

Question 14

What is the relationship between the equilibrium constant (K) and the Gibbs free energy change (ΔG) of a reaction at 298 K?

Accepted Answer

ΔG = -RTlnK

Answer

ΔG = RTlnK

Answer

K = -ΔG/RT

Answer

K = ΔG/RT

Question 15

Which of the following reactions represents a heterogeneous equilibrium?

Accepted Answer

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

Answer

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

Answer

2CO(g) + O2(g) <=> 2CO2(g)

Answer

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

Question 16

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

Accepted Answer

Infinity

Answer

0

Answer

1

Question 17

When the temperature of a system at equilibrium is raised, what happens to the equilibrium position if the reaction is endothermic?

Accepted Answer

Shifts right

Answer

Shifts left

Question 18

Which industrial process uses Le Chatelier's principle?

Accepted Answer

Production of ammonia

Answer

Smelting of iron ore

Answer

Refining of petroleum

Answer

Manufacture of plastics

Question 19

What is the purpose of a buffer solution in equilibrium experiments?

Accepted Answer

To prevent changes in pH

Answer

To increase the reaction rate

Answer

To decrease the equilibrium constant

Answer

To shift the equilibrium to the left

Question 20

Which reaction is a homogeneous equilibrium?

Accepted Answer

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

Answer

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

Answer

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

Answer

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

Question 21

Adding a catalyst to the equilibrium system: 2HI(g) <=> H2(g) + I2(g) has what effect?

Accepted Answer

Increases forward and reverse reaction rates equally

Answer

Shifts equilibrium towards more HI

Answer

Shifts equilibrium towards more H2 and I2

Answer

No effect on equilibrium position

Question 22

Which graph shows the correct relationship between reactant and product concentrations as equilibrium is approached?

Accepted Answer

Curve that initially increases and levels off

Answer

Straight line with positive slope

Answer

Straight line with negative slope

Answer

Curve that initially decreases and levels off

Question 23

A colorless solution contains the reaction: Fe3+(aq) + SCN-(aq) ⇌ [Fe(SCN)]2+(aq). What will happen to the color of the solution if excess thiocyanate ions (SCN-) are added? Explain your answer.

Accepted Answer

The solution will become colored as the equilibrium shifts to the right.

Answer

The solution will remain colorless as the equilibrium shifts to the left.

Answer

The solution will change color, but the equilibrium will not shift.

Answer

The solution will remain colorless, and the equilibrium will not shift.

Question 24

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

Accepted Answer

Volume of the reaction vessel

Answer

Temperature

Answer

Pressure

Answer

Concentration of reactants

Question 25

Consider the following equilibrium: 2 CO(g) + O2(g) <=> 2 CO2(g). If some CO2 is removed from the reaction mixture, what will happen to the forward rate of the reaction?

Accepted Answer

It will increase.

Answer

It will decrease.

Answer

It will remain the same.

Answer

It cannot be determined from the provided information.

Question 26

Which of the following is a weak acid?

Accepted Answer

CH3COOH

Answer

HCl

Answer

H2SO4

Answer

NaOH

Question 27

Which of the following salts will hydrolyze to produce an acidic solution?

Accepted Answer

NH4Cl

Answer

NaCl

Answer

Na2CO3

Answer

CH3COONa

Question 28

Consider the following reaction: A + B <=> C. If the equilibrium constant is large, what can you conclude about the relative amounts of reactants and products at equilibrium?

Accepted Answer

There will be much more C than A and B.

Answer

There will be much more A and B than C.

Answer

The amounts of A, B, and C will be roughly equal.

Answer

It cannot be determined from the provided information.

Question 29

Which of the following describes a key characteristic of heterogeneous equilibria?

Accepted Answer

Involves substances present in multiple phases

Answer

Involves substances present in a single phase

Answer

Does not involve chemical reactions

Answer

Is unaffected by temperature changes

Question 30

In enzyme kinetics, how is equilibrium theory utilized to quantify enzyme activity and understand the effects of inhibitors on enzyme-catalyzed reactions?

Accepted Answer

Equilibrium theory allows the determination of enzyme activity through the analysis of equilibrium constants in enzyme-catalyzed reactions.

Accepted Answer

Inhibitors can alter the equilibrium of enzyme-catalyzed reactions, affecting enzyme activity and providing insights into enzyme regulation.

Answer

Enzyme kinetics is not related to equilibrium theory.

Answer

Equilibrium theory is only applicable to inorganic reactions, not enzyme-catalyzed reactions.

Question 31

Which of the following factors will shift the equilibrium of the reaction N2(g) + 3H2(g) <=> 2NH3(g) to the right, favoring the formation of ammonia?

Accepted Answer

Increasing temperature

Answer

Decreasing pressure

Answer

Adding a catalyst

Answer

Adding nitrogen gas

Question 32

Which of the following processes is an example of a homogeneous equilibrium, where all reactants and products are in the same phase?

Accepted Answer

Mixing two gases

Answer

Dissolving salt in water

Answer

Precipitating a solid from a solution

Answer

Melting of ice

Question 33

The equilibrium constant for the reaction: Fe3+(aq) + SCN-(aq) <=> FeSCN2+(aq) is 1.0 × 10^2. What is the concentration of FeSCN2+ in a solution that contains 0.1 M Fe3+ and 0.2 M SCN-?

Accepted Answer

0.01 M

Answer

0.02 M

Answer

0.1 M

Answer

0.2 M

Question 34

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

Accepted Answer

Presence of a catalyst

Answer

Concentration of reactants

Answer

Temperature

Answer

Volume of the reaction vessel (at constant pressure)

Question 35

Consider the equilibrium: 2NO(g) + O2(g) <=> 2NO2(g). Which substance, when added, will shift the equilibrium to the right?

Accepted Answer

O2

Answer

NO

Answer

NO2

Answer

He

Question 36

Consider the equilibrium: H2(g) + I2(g) <=> 2HI(g). If the concentration of H2 is increased, what change will occur to the equilibrium position?

Accepted Answer

Shift to the right

Answer

Shift to the left

Answer

Remain unchanged

Answer

Cannot be determined

Question 37

Identify the weak acid among the following:

Accepted Answer

CH3COOH

Answer

HCl

Answer

H2SO4

Answer

HNO3

Question 38

Consider the equilibrium: BaSO4(s) <=> Ba2+(aq) + SO42-(aq). If the solubility product of BaSO4 is 1.0 x 10^-10, determine the molar solubility of BaSO4 in water.

Accepted Answer

1.0 x 10^-5 M

Answer

2.0 x 10^-5 M

Answer

3.0 x 10^-5 M

Answer

4.0 x 10^-5 M

Question 39

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

Accepted Answer

Surface area of the reactants

Answer

Temperature

Answer

Pressure

Answer

Concentration of reactants

Question 40

Consider the following equilibrium system: N2(g) + 3H2(g) <=> 2NH3(g). According to Le Chatelier's principle, if hydrogen gas is added to the system, what shift will occur?

Accepted Answer

The reaction will shift right to produce more products.

Answer

The reaction will shift left to produce more reactants.

Answer

The position of equilibrium will not change.

Answer

The equilibrium constant will increase.

Question 41

Which of the following industrial processes relies on the principles of chemical equilibrium?

Accepted Answer

Haber process

Answer

Electrolysis of water

Answer

Extraction of copper from its ore

Answer

Combustion of fuels

Question 42

Consider a closed system containing the following equilibrium: CO(g) + H2O(g) <=> CO2(g) + H2(g). What will happen to the partial pressure of carbon monoxide (CO) if the temperature is increased?

Accepted Answer

It will decrease.

Answer

It will increase.

Answer

It will remain the same.

Answer

It cannot be determined from the given information.

Question 43

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

Accepted Answer

Reaction between hydrogen and oxygen gases

Answer

Dissolution of sodium chloride in water

Answer

Precipitation of silver chloride from aqueous solutions

Answer

Decomposition of calcium carbonate

Question 44

Which of the following is a common application of buffer solutions?

Accepted Answer

Maintaining pH in biological systems

Answer

Neutralizing acids or bases

Answer

Preventing precipitation reactions

Answer

Separating ions by chromatography

Question 45

Which factor does NOT directly influence the equilibrium position of a chemical reaction?

Accepted Answer

Addition of a catalyst

Answer

Temperature

Answer

Concentration of reactants and products

Answer

Partial pressure of gases in the reaction

Question 46

Which is NOT a factor that can affect the position of a chemical equilibrium?

Accepted Answer

Type of reaction vessel

Answer

Temperature

Answer

Pressure

Answer

Concentration of reactants

Question 47

Which of the following species is a catalyst in the Haber process?

Accepted Answer

Iron

Answer

Nitrogen

Answer

Ammonia

Answer

Hydrogen

Question 48

Which of the following is a common ion effect?

Accepted Answer

The solubility of a sparingly soluble salt decreases when a soluble salt containing a common ion is added.

Answer

The rate of a reaction increases when a catalyst is added.

Question 49

Which of the following is a property of a buffer solution?

Accepted Answer

It resists changes in pH when small amounts of acid or base are added.

Answer

It has a pH of 7.

Answer

It is a strong electrolyte.

Question 50

Consider the following equilibrium system: H2O(l) ⇌ H+(aq) + OH-(aq). What is the relationship between the equilibrium constant, Kw, and the pH of the solution?

Accepted Answer

Kw = [H+][OH-]

Answer

Kw = pOH - pH

Answer

Kw = [H+]/[OH-]

Answer

Kw = pH + pOH

Question 51

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

Accepted Answer

2Fe3+(aq) + 2I-(aq) ⇌ 2Fe2+(aq) + I2(s)

Answer

2NH3(g) ⇌ N2(g) + 3H2(g)

Answer

CaCO3(s) ⇌ CaO(s) + CO2(g)

Answer

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

Question 52

For an endothermic reaction, what effect does increasing the temperature have on the equilibrium?

Accepted Answer

Shifts the equilibrium to the right (favoring products)

Answer

Shifts the equilibrium to the left (favoring reactants)

Answer

Has no effect on the equilibrium position

Question 53

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

Accepted Answer

Addition of a catalyst

Answer

Change in temperature

Answer

Change in volume of the container

Answer

Change in concentration of reactants or products

Question 54

Which of the following reactions represents a homogeneous equilibrium?

Accepted Answer

The dissolution of CO2 in water

Answer

The electrolysis of water

Answer

The reaction between iron and sulfur

Answer

The sublimation of iodine crystals

Question 55

Which reaction is NOT an equilibrium reaction?

Accepted Answer

2H2O (l) -> 2H2 (g) + O2 (g)

Answer

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

Answer

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

Answer

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

Question 56

Consider the equilibrium: Fe3+ (aq) + SCN- (aq) <=> Fe(SCN)2+ (aq). Which action will decrease the concentration of Fe(SCN)2+?

Accepted Answer

Adding Fe3+

Answer

Adding SCN-

Answer

Increasing the pressure

Answer

Decreasing the temperature

Question 57

What is a limitation of Le Chatelier's principle?

Accepted Answer

It does not predict the extent of the shift in equilibrium.

Answer

It is only valid for small changes in conditions.

Answer

It only applies to gas-phase reactions.

Question 58

Consider the equilibrium reaction: 2SO2(g) + O2(g) <=> 2SO3(g). What will happen to the concentration of SO3 if the temperature is increased?

Accepted Answer

Increase

Answer

Remain the same

Answer

Decrease