Equilibrium in Chemistry: A Comprehensive Guide for Biology Students

Question 1

Which characteristic identifies a system that has reached equilibrium?

Accepted Answer

Reactant and product concentrations remain constant.

Answer

Reactant concentrations exceed product concentrations.

Answer

The system is isolated from matter and energy exchange.

Answer

The system's temperature steadily rises.

Question 2

Which statement accurately describes chemical equilibrium?

Accepted Answer

A dynamic state where forward and reverse reactions occur at equal rates, resulting in no net change.

Answer

A static state where no further reaction takes place.

Answer

A state that can only be achieved in closed systems.

Answer

A state that is established instantaneously.

Question 3

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

Accepted Answer

Volume of the reaction vessel

Answer

Temperature

Answer

Pressure

Answer

Concentration of reactants

Question 4

Which property characterizes a weak acid?

Accepted Answer

Partially dissociates in water

Answer

Has a large equilibrium constant

Answer

Produces a high concentration of H+ ions

Answer

Completely dissociates in water

Question 5

What is the pH of a solution with a [H+] concentration of 10^-7 M?

Accepted Answer

7

Answer

0

Answer

10

Answer

14

Question 6

What is the Ka value for a weak acid with a pH of 3?

Accepted Answer

10^-3

Answer

10^-7

Answer

10^-11

Answer

10^-14

Question 7

The equilibrium constant (K) for a reaction represents:

Accepted Answer

The ratio of product to reactant concentrations at equilibrium

Answer

The rate at which the reaction proceeds to completion

Answer

The temperature at which the reaction reaches equilibrium

Answer

The time taken for the reaction to reach equilibrium

Question 8

According to Le Chatelier's principle, if the concentration of a reactant is increased in a reversible reaction, the equilibrium will shift:

Accepted Answer

To the right, favoring the production of products

Answer

To the left, favoring the production of reactants

Answer

Not at all, as the equilibrium is already established

Answer

In a random direction, depending on the specific reaction

Question 9

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

Accepted Answer

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

Answer

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

Answer

H2O(l) <=> H2O(g)

Answer

NH4Cl(aq) <=> NH4+(aq) + Cl-(aq)

Question 10

A large and positive equilibrium constant indicates that the reaction is:

Accepted Answer

Product-favored

Answer

Reactant-favored

Answer

Neither product- nor reactant-favored

Answer

Irreversible

Question 11

For the reaction A(g) + B(g) ⇌ C(g) + D(g), if the initial concentrations of A and B are both 1.0 M and the equilibrium concentration of C is 0.50 M, what is the equilibrium concentration of A?

Accepted Answer

0.75 M

Answer

0.50 M

Answer

1.00 M

Answer

1.50 M

Question 12

Which phenomenon is described as the common ion effect?

Accepted Answer

Decreased solubility of a sparingly soluble salt upon adding a common ion.

Answer

Increased pH of a weak acid solution upon adding a strong base.

Answer

Enhanced reaction rate with the addition of a catalyst.

Answer

Elevated boiling point of a liquid caused by a nonvolatile solute.

Question 13

Consider the reaction H2O(l) ⇌ H+(aq) + OH-(aq). Which action will lower the solution's pH?

Accepted Answer

Adding HCl

Answer

Adding NaOH

Answer

Raising the temperature

Answer

Reducing the solution volume

Question 14

Which factor does NOT influence the equilibrium constant of a reaction?

Accepted Answer

Chemical nature of reactants

Answer

Temperature

Answer

Pressure

Answer

Concentration of reactants

Question 15

Which characteristic defines a heterogeneous equilibrium?

Accepted Answer

Reactants and products exist in different phases.

Answer

Reactants and products exist in the same phase.

Answer

Equilibrium constant is expressed in terms of molarity.

Answer

Equilibrium constant is expressed in terms of partial pressures.

Question 16

Which of the following is NOT a condition that indicates chemical equilibrium?

Accepted Answer

Reactants and products are completely consumed

Answer

Concentrations of reactants remain constant over time

Answer

Forward and reverse reactions occur at equal rates

Answer

The Gibbs free energy of the system is minimized

Question 17

What is the value of the equilibrium constant (Kc) for a reaction with a reaction quotient (Q) equal to Kc?

Accepted Answer

Kc = Q

Answer

Kc > Q

Answer

Kc < Q

Answer

Kc = -Q

Question 18

Which of the following is NOT a factor that affects the rate of a chemical reaction?

Accepted Answer

Equilibrium constant

Answer

Temperature

Answer

Concentration of reactants

Answer

Surface area of reactants

Question 19

What is the 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 reversible, while heterogeneous equilibria are always irreversible

Answer

Homogeneous equilibria are affected by temperature only, while heterogeneous equilibria are affected by both temperature and pressure

Question 20

Which of the following is an example of a colligative property?

Accepted Answer

Boiling point elevation

Answer

Enthalpy change

Answer

Solubility

Answer

pH

Question 21

What is the relationship between the van't Hoff factor (i) and the number of particles produced by a solute?

Accepted Answer

i = number of particles produced

Answer

i = 1 / number of particles produced

Answer

i = square root of number of particles produced

Answer

i = log of number of particles produced

Question 22

Which of the following is NOT a type of intermolecular force?

Accepted Answer

Ionic bonding

Answer

Hydrogen bonding

Answer

Dipole-dipole interactions

Answer

London dispersion forces

Question 23

Consider the following reaction at equilibrium: A + B <=> C + D. If the concentration of reactant A is increased, which way will the reaction shift?

Accepted Answer

Right (forward direction)

Answer

Left (reverse direction)

Answer

Equilibrium position will not change

Answer

Reaction will proceed in both directions until all reactants are consumed

Question 24

For the reaction: 2NO(g) + O2(g) ⇌ 2NO2(g), which of the following correctly represents the equilibrium constant expression?

Accepted Answer

Kp = [NO2]^2 / [NO]^2[O2]

Answer

Kp = [NO]^2[O2] / [NO2]^2

Answer

Kp = [NO2]^2 / [NO][O2]

Answer

Kp = [NO]^2 / [NO2]^2[O2]

Question 25

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

Accepted Answer

Addition of a catalyst

Answer

Temperature

Answer

Pressure

Answer

Volume

Question 26

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

Accepted Answer

2SO2(g) + O2(g) ⇌ 2SO3(g)

Answer

CaCO3(s) ⇌ CaO(s) + CO2(g)

Answer

Fe(s) + 2HCl(aq) ⇌ FeCl2(aq) + H2(g)

Answer

CH4(g) + 2O2(g) → CO2(g) + 2H2O(l)

Question 27

Consider the equilibrium reaction: A(g) + B(g) ⇌ C(g) + D(g). If the concentration of A is doubled, what change will occur to the equilibrium concentration of C?

Accepted Answer

It will double.

Answer

It will halve.

Answer

It will remain the same.

Answer

It cannot be determined.

Question 28

Which of the following is the equilibrium constant expression for the dissociation of a weak acid, HA?

Accepted Answer

Ka = [H+][A-] / [HA]

Answer

Ka = [HA] / [H+][A-]

Answer

Ka = [HA][H+] / [A-]

Answer

Ka = [A-] / [H+][HA]

Question 29

Consider the reaction: 2CO(g) + O2(g) ⇌ 2CO2(g). If the temperature is increased, what change will occur to the equilibrium constant?

Accepted Answer

It will increase.

Answer

It will decrease.

Answer

It will remain the same.

Answer

It cannot be determined.

Question 30

Consider the equilibrium reaction: N2(g) + 3H2(g) <=> 2NH3(g). If the volume of the reaction container is decreased, which way will the equilibrium shift to re-establish equilibrium?

Accepted Answer

Left, decreasing NH3 concentration

Answer

Right, increasing NH3 concentration

Answer

No shift

Question 31

Consider the equilibrium reaction: N2 + 3H2 ⇌ 2NH3. If the partial pressure of H2 is doubled and the temperature is kept constant, what will happen to the equilibrium position?

Accepted Answer

Shift to the right (increase NH3 concentration)

Answer

Shift to the left (decrease NH3 concentration)

Answer

Cannot be determined without more information

Answer

Remain unchanged

Question 32

What is the value of the equilibrium constant (K) for a reaction that is at equilibrium?

Accepted Answer

Constant

Answer

Very small

Answer

Very large

Answer

Zero

Question 33

Which of the following factors affects the equilibrium constant of a reaction?

Accepted Answer

Temperature

Answer

Concentration of reactants and products

Answer

Presence of a catalyst

Question 34

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

Accepted Answer

Homogeneous equilibrium involves reactants and products in the same phase, while heterogeneous equilibrium involves reactants and products in different phases.

Answer

Homogeneous equilibrium involves solid reactants and products, while heterogeneous equilibrium involves gas phase reactants and products.

Answer

Homogeneous equilibrium involves only aqueous reactants and products, while heterogeneous equilibrium involves non-aqueous reactants and products.

Question 35

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

Accepted Answer

Ag+(aq) + Cl-(aq) ⇌ AgCl(s)

Answer

2NO2 ⇌ N2O4

Answer

2H2 + O2 ⇌ 2H2O

Answer

CH3COOH + H2O ⇌ CH3COO- + H3O+

Question 36

What is the purpose of using a buffer solution in an equilibrium experiment?

Accepted Answer

To maintain constant pH

Answer

To remove impurities

Answer

To prevent the reaction from occurring

Answer

To act as a catalyst

Question 37

For the reaction represented by aA + bB <=> cC + dD, the equilibrium constant expression, K, is:

Accepted Answer

K = ([C]^c[D]^d)/([A]^a[B]^b)

Answer

K = ([C]^c[D]^d) - ([A]^a[B]^b)

Answer

K = ([A]^a[B]^b)/([C]^c[D]^d)

Answer

K = ([A]^a[B]^b) + ([C]^c[D]^d)

Question 38

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

Accepted Answer

Catalyst

Answer

Pressure

Answer

Temperature

Answer

Concentration of reactants/products

Question 39

The equilibrium constant, K, provides information about the:

Accepted Answer

Relative amounts of reactants and products at equilibrium.

Answer

Direction of the reaction.

Answer

Rate of the reaction.

Question 40

For the reaction: 2NO(g) + O2(g) <=> 2NO2(g), the equilibrium constant expression is:

Accepted Answer

K = [NO2]^2/[NO]^2[O2]

Answer

K = [NO2]/[NO][O2]

Answer

K = [NO][O2]/[NO2]

Answer

K = [NO]^2[O2]/[NO2]^2

Question 41

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

Accepted Answer

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

Answer

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

Answer

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

Answer

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

Question 42

Which of the following statements accurately describes a chemical system at equilibrium?

Accepted Answer

The forward and reverse reactions are occurring at the same rate.

Answer

The forward reaction has ceased.

Answer

The concentrations of reactants and products are equal.

Question 43

A large equilibrium constant (Kc) indicates that at equilibrium:

Accepted Answer

The product concentration is significantly higher than the reactant concentration.

Answer

The reaction proceeds very slowly.

Answer

The reactant concentration is significantly higher than the product concentration.

Question 44

Consider the exothermic reaction: 2SO2(g) + O2(g) <=> 2SO3(g). Which change will shift the equilibrium to favor the formation of SO3?

Accepted Answer

Decreasing the temperature

Answer

Increasing the volume of the container

Answer

Adding a catalyst

Answer

Increasing the temperature

Question 45

For the reaction: H2(g) + I2(g) <=> 2HI(g), what happens to the equilibrium position when hydrogen gas (H2) is added to the equilibrium mixture at constant volume?

Accepted Answer

The equilibrium shifts to the right, favoring the formation of HI.

Answer

The equilibrium position remains unchanged.

Answer

The equilibrium shifts to the left, favoring the formation of H2 and I2.

Question 46

Which change will NOT affect the equilibrium position of the reaction: CaCO3(s) <=> CaO(s) + CO2(g)?

Accepted Answer

Adding more CaCO3(s)

Answer

Increasing the volume of the container

Answer

Increasing the pressure of CO2(g)

Answer

Removing some of the CO2(g)

Question 47

A reaction has an equilibrium constant (Kc) value of 1 x 10^-5. What can be concluded about this reaction?

Accepted Answer

The concentration of reactants is much higher than the concentration of products.

Answer

The concentration of products is much higher than the concentration of reactants.

Answer

The reaction proceeds very quickly.

Question 48

The Haber process (N2(g) + 3H2(g) <=> 2NH3(g)) is an industrially important process for ammonia production. It is typically conducted at high pressure. Why is high pressure preferred for maximizing ammonia yield?

Accepted Answer

High pressure shifts the equilibrium towards the side with fewer moles of gas, favoring ammonia formation.

Answer

High pressure increases the rate of both the forward and reverse reactions equally.

Question 49

A catalyst in a chemical reaction:

Accepted Answer

Provides an alternate reaction pathway with a lower activation energy.

Answer

Increases the concentration of reactants.

Answer

Shifts the equilibrium position towards the products.

Question 50

Consider the reaction: 2NO2(g) <=> N2O4(g). The mixture is initially brown due to the presence of NO2. If the pressure is increased, what would be the observed color change?

Accepted Answer

The mixture becomes lighter in color as the equilibrium shifts towards the colorless N2O4.

Answer

There is no color change observed.

Answer

The mixture becomes darker in color as the equilibrium shifts towards the brown NO2.