Chemical Equilibrium: A Comprehensive Guide for BEng Students

Question 1

Which of the following reactions is a heterogeneous equilibrium?

Accepted Answer

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

Answer

H2 + I2 <=> 2HI

Answer

NH3(aq) + H2O(l) <=> NH4+(aq) + OH-(aq)

Answer

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

Question 2

The equilibrium constant, Kc, for the reaction aA + bB <=> cC + dD is expressed as:

Accepted Answer

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

Answer

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

Answer

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

Answer

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

Question 3

The equilibrium constant for a reaction is related to the standard free energy change (ΔG°) by the equation:

Accepted Answer

Kc = exp(-ΔG°/RT)

Answer

Kc = exp(ΔG°/RT)

Answer

Kc = ΔG°/RT

Answer

Kc = -ΔG°/RT

Question 4

Which of the following is characteristic of a strong acid?

Accepted Answer

High equilibrium constant for dissociation

Answer

Low equilibrium constant for dissociation

Answer

Low concentration of H+ ions in solution

Answer

High concentration of OH- ions in solution

Question 5

The pH of a solution with a [H+] concentration of 1 × 10^-7 M is:

Accepted Answer

7

Answer

0

Answer

10

Answer

14

Question 6

A buffer solution is a solution that:

Accepted Answer

Resists changes in pH when small amounts of acid or base are added

Answer

Has a high concentration of H+ ions

Answer

Has a low concentration of OH- ions

Answer

Is always acidic

Question 7

Henry's law constant is defined as:

Accepted Answer

The proportionality constant relating the partial pressure of a gas to its concentration in a liquid

Answer

The equilibrium constant for the dissolution of a gas in a liquid

Answer

The solubility of a gas in a liquid at 1 atm pressure

Answer

The rate of diffusion of a gas through a liquid

Question 8

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

Accepted Answer

Addition of a catalyst

Answer

Concentration of reactants

Answer

Concentration of products

Answer

Temperature

Question 9

What is the equilibrium constant expression for the reaction: 2NO2(g) <=> N2O4(g)?

Accepted Answer

Kc = [N2O4] / [NO2]^2

Answer

Kc = [NO2]^2 / [N2O4]

Answer

Kc = [N2O4] / [NO2]

Answer

Kc = [NO2] / [N2O4]

Question 10

Consider the following reaction at equilibrium: CO(g) + 2H2(g) <=> CH3OH(g). If more hydrogen gas is added to the system, what will happen?

Accepted Answer

The equilibrium position will shift to the right (favor products).

Answer

The equilibrium position will shift to the left (favor reactants).

Answer

The equilibrium position will not change.

Answer

The reaction will proceed to completion.

Question 11

What is the equilibrium constant expression for the following reaction: 2NO(g) + O2(g) <=> 2NO2(g)?

Accepted Answer

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

Answer

K = [NO]^2/[O2]

Answer

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

Answer

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

Question 12

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

Accepted Answer

Net reaction rate is zero

Answer

Concentrations of reactants and products are equal

Answer

Forward and reverse reactions are occurring at unequal rates

Answer

Reaction is complete

Question 13

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

Accepted Answer

Reaction between two gases

Answer

Reaction between a solid and a gas

Answer

Reaction between a liquid and a gas

Answer

Reaction between a solid and a liquid

Question 14

Consider the following equilibrium: CO(g) + 2H2(g) <=> CH3OH(g). Which of the following changes to the system will increase the equilibrium constant?

Accepted Answer

Increasing the temperature

Answer

Decreasing the pressure

Answer

Adding an inert gas

Answer

Removing CH3OH from the reaction mixture

Question 15

Which of the following is a weak acid?

Accepted Answer

CH3COOH

Answer

HCl

Answer

H2SO4

Answer

HNO3

Question 16

Which of the following correctly defines chemical equilibrium?

Accepted Answer

A dynamic state where opposing reactions occur at equal rates.

Answer

A static state where no reactions occur.

Answer

A state where only the forward reaction occurs.

Answer

A state where only the reverse reaction occurs.

Question 17

A reaction with a large equilibrium constant is said to be:

Accepted Answer

Shifted to the right (favoring products)

Answer

Shifted to the left (favoring reactants)

Answer

At equilibrium

Answer

Neither favored in the forward nor reverse direction

Question 18

Which of the following is NOT a common buffer system?

Accepted Answer

NaOH/HCl

Answer

H2CO3/HCO3-

Answer

NH4+/NH3

Answer

CH3COOH/CH3COO-

Question 19

A titration is primarily used to determine the:

Accepted Answer

Concentration of an unknown acid or base

Answer

Equilibrium constant of a reaction

Answer

pH of a solution

Answer

Rate of a reaction

Question 20

A solution with a pH of 3 has a hydrogen ion concentration of:

Accepted Answer

1.0 x 10^-3 M

Answer

1.0 x 10^-7 M

Answer

1.0 x 10^-11 M

Answer

1.0 x 10^-13 M

Question 21

Which of the following does not affect the equilibrium position?

Accepted Answer

Catalyst

Answer

Temperature

Answer

Volume (for gas reactions)

Answer

Concentration of reactants and products

Question 22

A negative free energy change for a reaction indicates that it is:

Accepted Answer

Spontaneous

Answer

Non-spontaneous

Answer

At equilibrium

Answer

Slow

Question 23

A buffer solution is designed to:

Accepted Answer

Resist pH changes

Answer

Have a high H+ concentration

Answer

Have a low OH- concentration

Answer

Always be acidic

Question 24

Identify the weak base from the following:

Accepted Answer

NH3

Answer

NaOH

Answer

KOH

Answer

HCl

Question 25

What is the primary purpose of a titration?

Accepted Answer

Determining solution concentration

Answer

Measuring solution pH

Answer

Separating liquids

Answer

Purifying solids

Question 26

The equilibrium constant for a reaction that goes to completion is:

Accepted Answer

Infinity

Answer

0

Answer

1

Answer

Cannot be determined

Question 27

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

Accepted Answer

Type of reaction mechanism

Answer

Temperature

Answer

Pressure

Answer

Concentration of reactants and products

Question 28

Which expression represents the equilibrium constant (K) for the reaction: aA + bB ⇌ cC + dD?

Accepted Answer

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

Answer

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

Question 29

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

Accepted Answer

Concentration of products

Answer

Temperature

Answer

Pressure

Question 30

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

Accepted Answer

Shift to the right

Answer

Shift to the left

Answer

Remain unchanged

Question 31

In a closed system at equilibrium, what is the relationship between the forward and reverse reaction rates?

Accepted Answer

They are equal.

Answer

They are zero.