Chemistry 9th Chap 9 : Topic 1 - Maryam Publications

Chemistry Chapter 9 : Topic 1

Reversible Reactions

1 / 19

In a chemical reaction represented as:
N₂(g) + 3H₂(g) ⇌ 2NH₃(g)
The symbol (⇌) indicates that:

A) The reaction proceeds only in forward direction until all reactants are used up

B) The reaction is irreversible under all conditions

C) The reaction can proceed in both forward and backward directions under the same conditions

D) The products cannot react again to form reactants

2 / 19

A student observes that in a closed system, a chemical reaction does not stop completely even after a long time, and both reactants and products are present together. This behavior indicates that the reaction is:

A) Combustion reaction

B) Displacement reaction

C) Complete reaction

D) Reversible reaction reaching equilibrium

3 / 19

Which statement best explains why reversible reactions do not go to completion?

A) Catalysts stop the reaction midway

B) Products are always more stable than reactants

C) Products can react to reform reactants under the same conditions

D) Reactants completely lose energy during reaction

4 / 19

Consider the equilibrium system:
2SO₂(g) + O₂(g) ⇌ 2SO₃(g)
Which statement is correct?

A) Only reactants remain after reaction

B) Both reactants and products exist in dynamic balance

C) Reaction stops permanently after some time

D) Only SO₃ is present at the end

5 / 19

In a reversible reaction, what happens at equilibrium?

A) Reverse reaction becomes faster than forward reaction

B) All reactants are converted into products

C) Both forward and reverse reactions occur at equal rates

D) Forward reaction stops completely

6 / 19

Which of the following is the most appropriate interpretation of a reversible reaction symbol (⇌)?

A) Reaction is unidirectional but slow

B) Reaction occurs only under heating

C) Reaction cannot occur in a closed system

D) Reaction proceeds in both directions under same conditions

7 / 19

A chemical reaction is carried out in a closed container and after some time, no visible change is observed, but chemical analysis shows both reactants and products are present. This condition is called:

A) Equilibrium state

B) Completion point

C) Decomposition stage

D) Activation stage

8 / 19

Which of the following reactions is most likely reversible?

A) Formation of ammonia from nitrogen and hydrogen

B) Burning of magnesium in air

C) Rusting of iron

D) Explosion of firecracker

9 / 19

Why are reversible reactions important in industrial processes?

A) They always produce 100% yield.

B) They always proceed instantly.

C) They eliminate the need for catalysts.

D) They allow control over product formation by changing conditions.

10 / 19

Which condition is essential for establishing reversible reaction equilibrium?

A) Open container

B) Presence of solid only

C) Closed system

D) Constant removal of products

11 / 19

A reaction is represented as:
A+B ⇌ C+D
If both forward and reverse reactions continue at equal rates, it means:

A) Only forward reaction is occurring

B) Reaction has stopped completely

C) Reaction is irreversible

D) Dynamic equilibrium is established

12 / 19

Which statement correctly distinguishes reversible reactions from irreversible reactions?

A) Reversible reactions proceed in both directions under same conditions

B) Reversible reactions always produce heat

C) Irreversible reactions can also reach equilibrium

D) Irreversible reactions form no products

13 / 19

In a reversible reaction, why does the reaction not fully convert reactants into products?

A) Because equilibrium is reached where both reactions balance

B) Because catalysts stop working

C) Because reactants are always in excess

D) Because products are unstable in all cases

14 / 19

Which of the following best describes a reversible chemical system?

A) System where reaction stops after activation energy is consumed

B) System where products can reform reactants under same conditions

C) System with no energy changes

D) One-way conversion of reactants into products

15 / 19

What does the term “dynamic equilibrium” mean in reversible reactions?

A) Reaction has stopped completely

B) Both forward and reverse reactions continue at equal rates

C) Products are permanently stable

D) Only forward reaction is occurring

16 / 19

Why is the symbol (⇌) used instead of ( → ) in some chemical equations?

A) To show faster reaction

B) To show catalyst presence

C) To indicate reversible reaction occurring in both directions

D) To indicate irreversible reaction

17 / 19

A reaction reaches equilibrium in a closed flask. If more reactant is added, what will most likely happen?

A) Only reverse reaction occurs

B) Reaction stops permanently

C) No change occurs at all

D) System shifts to restore equilibrium

18 / 19

Which statement is TRUE about reversible reactions?

A) They always finish within seconds.

B) They cannot occur in nature.

C) They proceed in both directions depending on conditions.

D) They only occur in gases.

19 / 19

Which of the following best describes why reversible reactions are important in equilibrium chemistry?

A) They prevent formation of products.

B) They help explain why reactions stop before full completion.

C) They always destroy reactants completely.

D) They only occur in laboratory settings.

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