Chemical Equilibrium: Master the Dynamics of Reversible Reactions

Question 1

Which equation represents the relationship between the equilibrium constant (K) and the Gibbs free energy change (ΔG) at constant temperature?

Accepted Answer

K = -ΔG

Answer

K = ΔG

Answer

K is independent of ΔG

Question 2

Which of the following solutions exhibits the highest buffering capacity?

Accepted Answer

A solution with equal concentrations of a weak acid and its conjugate base

Answer

A solution with a high concentration of a weak acid and a low concentration of its conjugate base

Answer

A solution with a low concentration of a weak acid and a high concentration of its conjugate base

Answer

A solution with only a weak acid

Question 3

Which expression represents the equilibrium constant (Kc) for the following reaction: A + B ⇌ C + D?

Accepted Answer

Kc = [(C][D)] / [(A][B])

Answer

Kc = (C + D) / (A + B)

Answer

Kc = (A + B) / (C + D)

Answer

Kc = [(A][B)] / [(C][D])

Question 4

Consider the equilibrium: 2CO(g) + O2(g) ⇌ 2CO2(g). Which change will shift the equilibrium to the right, favouring the formation of CO2?

Accepted Answer

Increasing the concentration of O2

Answer

Decreasing the concentration of CO2

Answer

Increasing the volume of the container

Answer

Decreasing the temperature

Question 5

According to Le Chatelier's principle, what will happen to the equilibrium position of the reaction A + B ⇌ C + D when more reactant A is added?

Accepted Answer

The equilibrium will shift to the right.

Answer

The equilibrium will shift to the left.

Answer

The equilibrium will not change.

Answer

The reaction will proceed to completion.

Question 6

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

Accepted Answer

Presence of a catalyst

Answer

Temperature

Answer

Concentration of reactants and products

Answer

Pressure (for gas reactions)

Question 7

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

Accepted Answer

Dissolution of salt in water

Answer

Vaporization of water

Answer

Neutralization of an acid and a base

Answer

Combustion of methane

Question 8

What is the relationship between the standard free energy change (ΔG°) and the equilibrium constant (K)?

Accepted Answer

ΔG° = -RTlnK

Answer

ΔG° = RTlnK

Answer

ΔG° = -KlnRT

Answer

ΔG° = KlnRT

Question 9

Which of the following graphs represents the typical change in the concentrations of reactants and products over time as a reaction approaches equilibrium?

Accepted Answer

A curve that approaches a horizontal line.

Answer

A straight line that slopes upwards.

Answer

A parabola that opens upwards.

Answer

A bell-shaped curve.

Question 10

Consider the equilibrium: N2(g) + 3H2(g) ⇌ 2NH3(g). Which change will shift the equilibrium towards the product side?

Accepted Answer

Increasing the temperature

Answer

Decreasing the pressure

Answer

Adding more N2 gas

Answer

Removing H2 gas

Question 11

Consider the equilibrium: Fe3+(aq) + SCN-(aq) ⇌ FeSCN2+(aq). This reaction produces a deep red colour in solution. What will happen to the colour of the solution if more Fe3+ ions are added?

Accepted Answer

Colour becomes more intense (darker red)

Answer

Colour becomes less intense (lighter red)

Answer

No change in colour

Answer

The solution turns blue

Question 12

Consider the equilibrium reaction: N2(g) + 3H2(g) <=> 2NH3(g). According to Le Chatelier's principle, what will happen to the equilibrium position if the concentration of H2 is increased?

Accepted Answer

Equilibrium will shift to the right, favoring NH3.

Answer

Equilibrium will shift to the left, favoring N2 and H2.

Answer

Equilibrium will remain unchanged.

Answer

Equilibrium will shift to the left, but only slightly.

Question 13

Which of the following factors does NOT affect the equilibrium position of a reaction, according to Le Chatelier's principle?

Accepted Answer

Addition or removal of solid reactants or products.

Answer

Temperature

Answer

Volume

Answer

Concentration of reactants

Question 14

Which of the following acids is the weakest?

Accepted Answer

Acetic acid

Answer

Hydrochloric acid

Answer

Nitric acid

Answer

Phosphoric acid

Question 15

Express the equilibrium constant expression for the reaction: N2 (g) + 3H2 (g) ⇌ 2NH3 (g).

Accepted Answer

K = [N2][H2]^3/[NH3]^2

Answer

K = [NH3]^2/[N2][H2]^3

Answer

K = [N2][H2]/[NH3]^2

Answer

K = [NH3]^2/[N2][H2]

Question 16

Which of the following is classified as a strong acid?

Accepted Answer

Hydrochloric acid

Answer

Acetic acid

Answer

Carbonic acid

Answer

Ammonia

Question 17

Which of the following is a titrimetric method commonly used to determine the concentration of an unknown acid?

Accepted Answer

Neutralisation titration

Answer

Redox titration

Answer

Gravimetric analysis

Answer

Spectrophotometry

Question 18

Identify the conjugate acid of NH3.

Accepted Answer

NH4+

Answer

OH-

Answer

H3O+

Answer

NO3-

Question 19

Which of the following statements describes the common ion effect?

Accepted Answer

The solubility of a sparingly soluble salt decreases when a common ion is added to the solution.

Answer

The pH of a solution increases when a common ion is added to the solution.

Answer

The rate of a reaction increases when a common ion is added to the solution.

Answer

The equilibrium constant of a reaction changes when a common ion is added to the solution.

Question 20

Consider the following reaction: H2CO3(aq) + H2O(l) ⇌ H3O+(aq) + HCO3-(aq). Which of the following would increase the pH of the solution?

Accepted Answer

Adding NaOH

Answer

Adding HCl

Answer

Adding H2CO3

Answer

Adding HCO3-

Question 21

Which of the following is a weak acid?

Accepted Answer

CH3COOH

Answer

HCl

Answer

H2SO4

Answer

HNO3

Question 22

Which of the following is considered a buffer solution?

Accepted Answer

A solution containing a weak acid and its salt

Answer

A solution containing a strong acid and its salt

Answer

A solution containing only a strong acid

Answer

A solution containing only a weak base

Question 23

Which of the following is the equilibrium constant expression for the reaction: 2NO(g) + O2(g) ⇌ 2NO2(g)?

Accepted Answer

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

Answer

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

Answer

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

Answer

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

Question 24

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

Accepted Answer

Magnetic field

Answer

Temperature

Answer

Concentration of reactants

Answer

Pressure

Question 25

Consider the equilibrium: CaCO3(s) ⇌ CaO(s) + CO2(g). What will happen to the equilibrium position if the pressure of CO2 is increased?

Accepted Answer

Shift to the right

Answer

Shift to the left

Answer

No change

Question 26

What is the value of the equilibrium constant for a reaction that has reached equilibrium?

Accepted Answer

Positive

Answer

Zero

Answer

Negative

Answer

Infinity

Question 27

Which of the following is a weak acid?

Accepted Answer

CH3COOH

Answer

HCl

Answer

H2SO4

Answer

HNO3

Question 28

Calculate the pH of a solution with [H+] = 1 x 10^-5 M?

Accepted Answer

5

Answer

2

Answer

7

Answer

9

Question 29

Which of the following is a buffer solution?

Accepted Answer

Solution of a weak acid and its conjugate base

Answer

Solution of a strong acid and its conjugate base

Answer

Solution of a salt and water

Answer

Solution of a base and its conjugate acid

Question 30

Which of the following is classified as a weak acid?

Accepted Answer

Acetic acid (CH3COOH)

Answer

Hydrochloric acid (HCl)

Answer

Sulfuric acid (H2SO4)

Answer

Nitric acid (HNO3)

Question 31

What is the pH of a 0.1 M aqueous solution of sodium hydroxide (NaOH)?

Accepted Answer

13

Answer

1

Answer

7

Answer

14

Question 32

Which of the following is considered a buffer solution?

Accepted Answer

A mixture of a weak acid and its conjugate base

Answer

A solution with a high concentration of H+ ions

Answer

A solution with a high concentration of OH- ions

Answer

A solution with a pH of 7

Question 33

Which of the following is a weak base?

Accepted Answer

Ammonium hydroxide (NH4OH)

Answer

Sodium hydroxide (NaOH)

Answer

Potassium hydroxide (KOH)

Answer

Calcium hydroxide (Ca(OH)2)

Question 34

Which of the following is a weak electrolyte?

Accepted Answer

CH3COOH

Answer

HCl

Answer

NaCl

Answer

NaOH

Question 35

Which indicator changes colour at a pH of approximately 7?

Accepted Answer

Litmus

Answer

Methyl orange

Answer

Phenolphthalein

Answer

Universal indicator

Question 36

Which of the following is a buffer solution?

Accepted Answer

A solution of a weak acid and a salt of that acid

Answer

A solution of a strong acid and a strong base

Answer

A solution of a strong base and a salt of that base

Answer

A solution of pure water

Question 37

Consider the reaction: A + 2B <=> C. If the initial concentrations of A, B, and C are all 1 M, and the equilibrium concentration of C is 0.5 M, calculate the equilibrium concentration of A.

Accepted Answer

0.25 M

Answer

0.5 M

Answer

1 M

Answer

2 M

Question 38

Which of the following reactions will proceed spontaneously in the forward direction?

Accepted Answer

E + F <=> G + H (ΔG < 0)

Answer

A + B <=> C + D (ΔG > 0)

Answer

I + J <=> K + L (ΔG = 0)

Answer

M + N <=> O + P (ΔG = +10 kJ/mol)

Question 39

In a chemical equilibrium, the forward and reverse reactions occur at

Accepted Answer

the same rate.

Answer

different rates.

Answer

random rates.

Answer

predictable rates.

Question 40

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

Accepted Answer

Amount of product

Answer

Temperature

Answer

Pressure

Answer

Concentration of reactants

Question 41

An equilibrium constant of 10 indicates that

Accepted Answer

the reaction favours the formation of products.

Answer

the forward reaction is 10 times faster than the reverse reaction.

Answer

the equilibrium mixture contains 10 times more products than reactants.

Answer

the reaction is irreversible.

Question 42

Which change would increase the equilibrium yield of HI in the reaction: H2(g) + I2(g) <=> 2HI(g)?

Accepted Answer

Increasing the pressure

Answer

Decreasing the temperature

Answer

Removing some HI(g)

Answer

Adding an inert gas

Question 43

In the equilibrium reaction: 2H2(g) + O2(g) <=> 2H2O(g), which species acts as a catalyst?

Accepted Answer

There is no catalyst in this reaction.

Answer

H2(g)

Answer

O2(g)

Answer

H2O(g)

Question 44

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

Accepted Answer

Presence of a catalyst

Answer

Temperature

Answer

Pressure

Answer

Concentration of reactants

Question 45

Consider the equilibrium: CO(g) + H2O(g) ⇌ CO2(g) + H2(g). Which change would result in an increase in the partial pressure of H2?

Accepted Answer

Removing some H2O

Answer

Adding more CO

Answer

Decreasing the temperature

Answer

Increasing the volume of the container

Question 46

Which of the following is classified as a weak acid?

Accepted Answer

Acetic acid

Answer

Hydrochloric acid

Answer

Nitric acid

Answer

Sulfuric acid

Question 47

Determine the equilibrium constant expression for the reaction: N2(g) + 3H2(g) ⇌ 2NH3(g).

Accepted Answer

Keq = [N2][H2]^3/[NH3]^2

Answer

Keq = [NH3]^2/[N2][H2]^3

Answer

Keq = 1/[N2][H2]^3]

Answer

Keq = [N2][H2]^3/[NH3]^4

Question 48

Consider the equilibrium: 2CO(g) + O2(g) ⇌ 2CO2(g). Which action will shift the equilibrium towards the formation of CO2?

Accepted Answer

Increase in temperature

Answer

Decrease in pressure

Answer

Addition of more CO

Answer

Addition of a catalyst

Question 49

Which effect refers to the decrease in solubility of a sparingly soluble salt when a strong electrolyte containing a common ion is added?

Accepted Answer

Common ion effect

Answer

Salt effect

Answer

Solubility effect

Answer

Ionization effect

Question 50

Which of the following does not influence the equilibrium position?

Accepted Answer

Identity of reactants and products

Answer

Temperature

Answer

Pressure

Answer

Concentrations of reactants and products

Question 51

Identify the conjugate acid-base pair for the weak base NH3.

Accepted Answer

NH3, NH4+

Answer

NH4+, NH2-

Answer

H+, NH3

Answer

OH-, NH4+

Question 52

Determine the correct formula for calculating the pH of a buffer solution.

Accepted Answer

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

Answer

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

Answer

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

Answer

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

Question 53

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

Accepted Answer

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

Answer

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

Answer

Kc = [NO2] / [NO][O2]

Answer

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

Question 54

For the reaction: 2Fe(s) + 3Cl2(g) <=> 2FeCl3(s), predict the equilibrium shift if the concentration of Cl2(g) is increased.

Accepted Answer

Equilibrium shifts to the right

Answer

Equilibrium shifts to the left

Answer

No effect on equilibrium

Answer

Cannot be determined

Question 55

What is the purpose of using a buffer solution?

Accepted Answer

To resist changes in pH

Answer

To determine the pH of a solution

Answer

To catalyze a reaction

Answer

To prevent precipitation

Question 56

What is the primary function of an indicator in a titration?

Accepted Answer

To indicate the endpoint of the titration

Answer

To determine the volume of acid or base added

Answer

To catalyze the reaction

Answer

To prevent side reactions

Question 57

Which of the following expressions represents the equilibrium constant, Kc, for the reaction: 2NO(g) + O2(g) ⇌ 2NO2(g)?

Accepted Answer

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

Answer

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

Answer

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

Question 58

According to Le Chatelier's principle, if the temperature of an endothermic reaction is increased, what will happen to the equilibrium position?

Accepted Answer

Equilibrium will shift to the right to absorb heat.

Answer

Equilibrium will not be affected.

Answer

Reaction rate will increase.

Answer

Equilibrium will shift to the left to release heat.

Question 59

Which of the following will cause the equilibrium of the reaction: N2(g) + 3H2(g) ⇌ 2NH3(g) to shift towards the products?

Accepted Answer

Increasing the pressure

Answer

Adding a catalyst

Answer

Removing NH3 from the system

Answer

Decreasing the temperature

Question 60

Which of the following is considered a weak acid?

Accepted Answer

H2CO3

Answer

NaOH

Answer

KOH

Answer

HCl

Question 61

What is the conjugate base of HCO3-?

Accepted Answer

CO3^2-

Answer

HCO3-

Answer

OH-

Answer

H2CO3

Question 62

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

Accepted Answer

A solution that resists changes in pH when small amounts of acid or base are added.

Answer

A solution with a low concentration of OH-

Answer

A solution with a high concentration of H+

Answer

A solution with a pH of 7

Question 63

What occurs at the equivalence point in a titration?

Accepted Answer

The moles of acid added are equal to the moles of base initially present, and the solution is exactly neutralized.

Answer

The color of the indicator changes.

Answer

The pH of the solution is 7.

Question 64

The reaction: H2(g) + I2(g) <=> 2HI(g) has an equilibrium constant, Kc, of 50 at a given temperature. If the initial concentrations of both H2 and I2 are 0.10 mol/dm³, what is the equilibrium concentration of HI?

Accepted Answer

0.19 mol/dm³

Answer

0.20 mol/dm³

Answer

0.05 mol/dm³

Answer

0.10 mol/dm³