30 Chemical Equilibrium Quiz Questions and Answers

Chemical equilibrium is a fundamental concept in chemistry that describes the state in which a chemical reaction reaches a balance, and the concentrations of reactants and products remain constant over time. At equilibrium, the forward and reverse reactions occur at equal rates, leading to a dynamic state where the concentrations of reactants and products do not change on a macroscopic scale.

The concept of chemical equilibrium is based on the law of mass action, which states that the rate of a chemical reaction is directly proportional to the product of the concentrations of the reactants. As a reaction progresses, the concentrations of reactants decrease, and those of products increase until the rates of the forward and reverse reactions become equal.

Chemical equilibrium is characterized by specific equilibrium constants, such as the equilibrium constant (Kc) for reactions involving concentrations and the equilibrium constant (Kp) for reactions involving partial pressures. The value of the equilibrium constant depends on the stoichiometry of the balanced chemical equation and is temperature-dependent.

Reversible reactions, where both forward and reverse reactions occur simultaneously, are essential for achieving chemical equilibrium. Factors that influence equilibrium include temperature, pressure, and the presence of catalysts. By understanding chemical equilibrium, scientists can predict reaction outcomes, optimize reaction conditions, and design chemical processes with maximum efficiency and yield. The concept plays a crucial role in various fields, including industrial chemistry, environmental science, and biochemistry.

In this article

• Part 1: 30 chemical equilibrium quiz questions & answers
• Part 2: Download chemical equilibrium questions & answers for free
• Part 3: Free online quiz creator – OnlineExamMaker

Part 1: 30 chemical equilibrium quiz questions & answers

1. Chemical equilibrium occurs when:
a) The rate of the forward reaction is equal to the rate of the reverse reaction.
b) The concentration of reactants is higher than the concentration of products.
c) The reaction has stopped completely.
d) The reaction is irreversible.
Answer: a) The rate of the forward reaction is equal to the rate of the reverse reaction.

2. Which factor does NOT affect the position of chemical equilibrium?
a) Temperature
b) Pressure
c) Concentration of reactants and products
d) Presence of a catalyst
Answer: d) Presence of a catalyst

3. The equilibrium constant (Kc) for a chemical reaction is:
a) The ratio of the rate constants for the forward and reverse reactions.
b) The ratio of the concentrations of products to reactants at equilibrium.
c) The ratio of the concentrations of reactants to products at equilibrium.
d) The sum of the concentrations of reactants and products at equilibrium.
Answer: b) The ratio of the concentrations of products to reactants at equilibrium.

4. At equilibrium, the Gibbs free energy change (ΔG) of a reaction is:
a) Positive
b) Negative
c) Zero
d) Constant
Answer: c) Zero

5. A decrease in temperature would shift the equilibrium position of an exothermic reaction to:
a) The left (reactants side)
b) The right (products side)
c) It would not change the equilibrium position
d) Both left and right simultaneously
Answer: a) The left (reactants side)

6. Le Chatelier’s principle states that if an external stress is applied to a system at equilibrium:
a) The system will absorb the stress and remain at equilibrium.
b) The system will resist the stress and shift the equilibrium position to relieve the stress.
c) The system will stop reacting to avoid any changes.
d) The stress will have no effect on the equilibrium.
Answer: b) The system will resist the stress and shift the equilibrium position to relieve the stress.

7. When the concentration of products is much higher than the concentration of reactants at equilibrium, the equilibrium constant (Kc) will be:
a) Close to zero
b) Very large
c) Equal to 1
d) Unaffected by the concentrations
Answer: b) Very large

8. A reaction with an equilibrium constant (Kc) value of 1 means that:
a) The reaction does not reach equilibrium.
b) The reactants are favored at equilibrium.
c) The products are favored at equilibrium.
d) The reaction has equal concentrations of reactants and products at equilibrium.
Answer: d) The reaction has equal concentrations of reactants and products at equilibrium.

9. A catalyst affects the equilibrium position of a chemical reaction by:
a) Increasing the rate of the forward reaction only.
b) Increasing the rate of the reverse reaction only.
c) Increasing the rates of both the forward and reverse reactions proportionally.
d) Not affecting the equilibrium position at all.
Answer: d) Not affecting the equilibrium position at all.

10. In a dynamic equilibrium, which of the following statements is true?
a) The concentration of reactants is higher than the concentration of products.
b) The rate of the forward reaction is higher than the rate of the reverse reaction.
c) The concentrations of reactants and products remain constant over time.
d) The reaction has stopped completely.
Answer: c) The concentrations of reactants and products remain constant over time.

11. An increase in pressure would favor the equilibrium position of a reaction involving:
a) Gases with an equal number of moles on both sides of the balanced equation.
b) Gases with fewer moles on both sides of the balanced equation.
c) Gases with more moles on both sides of the balanced equation.
d) Gases with no moles on both sides of the balanced equation.
Answer: a) Gases with an equal number of moles on both sides of the balanced equation.

12. The equilibrium constant (Kc) for a chemical reaction can be influenced by:
a) The initial concentrations of reactants and products.
b) The size of the reaction vessel.
c) The presence of a catalyst.
d) The temperature of the reaction.
Answer: d) The temperature of the reaction.

13. Which statement is true regarding a reaction at equilibrium?
a) The concentration of reactants decreases with time.
b) The concentration of products increases with time.
c) The forward reaction completely stops.
d) The rate of the forward reaction equals the rate of the reverse reaction.
Answer: d) The rate of the forward reaction equals the rate of the reverse reaction.

14. A system is at equilibrium when:
a) The concentration of products is higher than the concentration of reactants.
b) The concentration of reactants is higher than the concentration of products.
c) The concentrations of reactants and products remain constant over time.
d) The reaction has not yet started.
Answer: c) The concentrations of reactants and products remain constant over time.

15. How does an increase in temperature affect an endothermic reaction at equilibrium?
a) It shifts the equilibrium to the left.
b) It shifts the equilibrium to the right.
c) It has no effect on the equilibrium position.
d) It increases the rate of the reaction.
Answer: b) It shifts the equilibrium to the right.

Part 2: Download chemical equilibrium questions & answers for free

16. Which of the following statements about equilibrium constants is true?
a) Equilibrium constants are dimensionless quantities.
b) Equilibrium constants are affected by changes in pressure.
c) Equilibrium constants are determined experimentally, not theoretically.
d) Equilibrium constants are the same for all reactions at a given temperature.
Answer: a) Equilibrium constants are dimensionless quantities.

17. In a chemical equilibrium, the value of the equilibrium constant (Kc) is:
a) Constant and independent of temperature.
b) Constant and independent of the initial concentrations of reactants and products.
c) Different for the forward and reverse reactions.
d) Affected by the presence of a catalyst.
Answer: b) Constant and independent of the initial concentrations of reactants and products.

18. If the value of the equilibrium constant (Kc) for a reaction is very small, it indicates that:
a) The reaction does not reach equilibrium.
b) The reaction heavily favors the products.
c) The reaction heavily favors the reactants.
d) The reaction has equal concentrations of reactants and products at equilibrium.
Answer: c) The reaction heavily favors the reactants.

19. A reaction is initially at equilibrium. If additional reactants are added, the equilibrium will shift:
a) To the left, favoring the reactants.
b) To the right, favoring the products.
c) Equilibrium will not shift; it remains unchanged.
d) It depends on the nature of the reactants and products.
Answer: a) To the left,

favoring the reactants.

20. The solubility product constant (Ksp) applies to which type of equilibrium?
a) Gas-liquid equilibrium
b) Solid-gas equilibrium
c) Solid-liquid equilibrium
d) Liquid-liquid equilibrium
Answer: c) Solid-liquid equilibrium

21. Which of the following is an example of a heterogeneous equilibrium?
a) N2 + 3H2 ↔ 2NH3
b) CO2 + H2O ↔ H2CO3
c) CaCO3(s) ↔ CaO(s) + CO2(g)
d) 2SO2(g) + O2(g) ↔ 2SO3(g)
Answer: c) CaCO3(s) ↔ CaO(s) + CO2(g)

22. If the equilibrium constant (Kc) for a reaction is very large, it indicates that:
a) The reaction heavily favors the reactants.
b) The reaction heavily favors the products.
c) The reaction does not reach equilibrium.
d) The reaction has equal concentrations of reactants and products at equilibrium.
Answer: b) The reaction heavily favors the products.

23. Which of the following is an example of a reversible reaction?
a) AgNO3 + NaCl → AgCl + NaNO3
b) CaCO3 → CaO + CO2
c) C6H12O6 + 6O2 → 6CO2 + 6H2O
d) 2Na + Cl2 → 2NaCl
Answer: a) AgNO3 + NaCl → AgCl + NaNO3

24. If the pressure of a gaseous reaction at equilibrium is increased, the equilibrium will shift:
a) To the left, favoring the reactants.
b) To the right, favoring the products.
c) Equilibrium will not shift; it remains unchanged.
d) It depends on the nature of the reactants and products.
Answer: d) It depends on the nature of the reactants and products.

25. The common ion effect describes the phenomenon when the addition of an ion that is already present in the equilibrium mixture:
a) Shifts the equilibrium position to the left.
b) Shifts the equilibrium position to the right.
c) Does not affect the equilibrium position.
d) Disrupts the equilibrium and causes the reaction to stop.
Answer: a) Shifts the equilibrium position to the left.

26. The reaction quotient (Qc) is used to determine:
a) The rate of a reaction at equilibrium.
b) The concentration of reactants and products at equilibrium.
c) The direction in which a reaction will proceed to reach equilibrium.
d) The change in Gibbs free energy (∆G) of a reaction at equilibrium.
Answer: c) The direction in which a reaction will proceed to reach equilibrium.

27. Which of the following statements about equilibrium constants (Kc) is true?
a) Kc values can be negative.
b) Kc values are affected by changes in pressure and temperature.
c) Kc values are expressed in units of moles per liter (mol/L).
d) Kc values are not dependent on the balanced chemical equation.
Answer: c) Kc values are expressed in units of moles per liter (mol/L).

28. For an exothermic reaction, an increase in temperature would shift the equilibrium position to:
a) The left, favoring the reactants.
b) The right, favoring the products.
c) Either left or right depending on other factors.
d) It will not affect the equilibrium position.
Answer: a) The left, favoring the reactants.

29. Which of the following statements about equilibrium is correct?
a) Equilibrium is a static state where no changes occur.
b) Equilibrium can be achieved only in a closed system.
c) Equilibrium is established when all reactants are completely converted to products.
d) Equilibrium is a dynamic state where forward and reverse reactions occur at the same rate.
Answer: d) Equilibrium is a dynamic state where forward and reverse reactions occur at the same rate.

30. In a dynamic equilibrium, which of the following is true?
a) The reaction has stopped completely.
b) The concentrations of reactants and products remain constant over time.
c) The concentration of products is higher than the concentration of reactants.
d) The rate of the forward reaction is higher than the rate of the reverse reaction.
Answer: b) The concentrations of reactants and products remain constant over time.

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