Questions on Reversible Reaction
Multiple-Choice Questions: Reversible Reaction
1. What is a reversible reaction?
A) A reaction that never stops
B) A reaction that cannot proceed backward
C) A reaction where products can revert to reactants
D) A reaction that involves only gases
E) A reaction that requires a catalyst
2. In a reversible reaction at equilibrium:
A) Only the forward reaction continues
B) The reverse reaction stops
C) Both forward and reverse reactions occur at the same rate
D) No reactions are occurring
E) Only products are present
3. Which of the following symbols represents a reversible reaction?
A) →
B) ←
C) ⇌
D) ↠
E) =
4. At equilibrium in a reversible reaction, the concentrations of reactants and products:
A) Become zero
B) Keep increasing
C) Are equal
D) Remain constant
E) Stop changing because the reaction stops
5. Which of the following factors does NOT affect the position of equilibrium in a reversible reaction?
A) Temperature
B) Catalyst
C) Pressure (for gases)
D) Concentration
E) Volume (for gases)
6. What effect does a catalyst have on a reversible reaction?
A) Increases yield of product
B) Changes the equilibrium position
C) Speeds up both forward and reverse reactions equally
D) Inhibits the reverse reaction
E) Lowers only the forward activation energy
7. In a closed system, a reversible reaction:
A) Reaches equilibrium
B) Stops completely
C) Becomes irreversible
D) Continues until all reactants are used
E) Forms a precipitate
8. Which of the following best describes chemical equilibrium?
A) Products are forming faster than reactants
B) Reactants are completely used
C) Forward and reverse reaction rates are equal
D) Forward reaction stops
E) Concentration of products keeps increasing
9. A system is at equilibrium. What will happen if more reactant is added?
A) Nothing will happen
B) The equilibrium shifts to the right
C) The equilibrium shifts to the left
D) The reverse reaction stops
E) The reaction becomes irreversible
10. Which of the following is true of a reversible reaction?
A) It can proceed in one direction only
B) The products cannot form reactants again
C) Reactants can form products and vice versa
D) It cannot reach equilibrium
E) It only occurs in aqueous solution
11. When a reversible reaction reaches equilibrium:
A) The reaction has stopped
B) Only products remain
C) The concentrations of all substances are zero
D) The forward and reverse reactions continue at equal rates
E) The energy is at maximum
12. Le Chatelier’s Principle applies to:
A) Only irreversible reactions
B) Only physical changes
C) Systems at equilibrium
D) Endothermic reactions only
E) Reactions in open systems only
13. In an exothermic reversible reaction, increasing the temperature will:
A) Shift the equilibrium to the right
B) Have no effect
C) Shift the equilibrium to the left
D) Stop the reaction
E) Increase product formation
14. What happens if the pressure is increased in a gaseous reversible reaction where more moles of gas are on the left side?
A) Equilibrium shifts to the left
B) Equilibrium shifts to the right
C) Reaction stops
D) Pressure has no effect
E) Temperature increases
15. Which of the following reactions is reversible?
A) Combustion of methane
B) Neutralization between strong acid and base
C) N2 + 3H2 ⇌ 2NH3
D) Precipitation of silver chloride
E) Decomposition of potassium chlorate
16. What does dynamic equilibrium mean?
A) No change in concentration because reactions have stopped
B) No further collisions occur
C) Forward and reverse reactions are still happening at the same rate
D) The reaction is finished
E) Energy stops flowing
17. Which statement is true about a reversible reaction not at equilibrium?
A) The forward and reverse rates are equal
B) It is always endothermic
C) The system is static
D) Net change in concentration still occurs
E) The reaction stops completely
18. If the concentration of products in a reversible reaction increases, what happens?
A) Equilibrium shifts to the right
B) Equilibrium shifts to the left
C) Nothing changes
D) Reaction becomes irreversible
E) Reactants become catalysts
19. Why is a closed system necessary for equilibrium?
A) To remove the products quickly
B) To prevent catalyst degradation
C) To allow reversible reactions to proceed without loss of materials
D) To supply excess energy
E) To change the phase of the reactants
20. Which of the following is NOT a characteristic of a reversible reaction at equilibrium?
A) Dynamic in nature
B) Constant macroscopic properties
C) Equal concentration of reactants and products
D) Forward and reverse rates are equal
E) System is in a closed container
Answer Key with Explanations
1. C – A reversible reaction is one in which products can revert to reactants.
2. C – At equilibrium, forward and reverse reactions occur at the same rate.
3. C – ⇌ is the symbol for a reversible reaction.
4. D – At equilibrium, concentrations remain constant, not necessarily equal.
5. B – A catalyst affects the rate, not the equilibrium position.
6. C – A catalyst speeds up both directions of the reaction equally.
7. A – In a closed system, reversible reactions reach equilibrium.
8. C – Equilibrium is defined by equal rates of forward and reverse reactions.
9. B – Adding reactant shifts the equilibrium to the right (toward products).
10. C – A reversible reaction allows reactants ⇌ products.
11. D – At equilibrium, both reactions continue at the same rate.
12. C – Le Chatelier’s Principle applies to systems at equilibrium.
13. C – In an exothermic reaction, increasing temperature favors the reverse (endothermic) direction.
14. B – Increased pressure shifts equilibrium to the side with fewer gas molecules (right side).
15. C – The Haber process (formation of NH₃) is reversible.
16. C – Dynamic equilibrium means reactions still occur, but net change is zero.
17. D – If not at equilibrium, net change in concentration still occurs.
18. B – Increased products shift equilibrium to the left (to form more reactants).
19. C – A closed system prevents loss of reactants/products, allowing equilibrium.
20. C – At equilibrium, concentrations are constant but not necessarily equal.
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