chemistry : class11 Dynamic Equilibrium : Equilibrium in chemical processes : Equilibrium MCQ Questions and Answers
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Dynamic Equilibrium
MCQ questions and answers.
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MCQ Questions
1. What is meant by dynamic equilibrium in a reversible chemical reaction?
A.
The reaction has completely stopped
B.
The forward and reverse reactions occur at equal rates
C.
Only the forward reaction occurs
D.
Only the reverse reaction occurs
Correct Answer:
The forward and reverse reactions occur at equal rates
Explanation:
At dynamic equilibrium, the forward and reverse reactions continue simultaneously at equal rates, so there is no overall change in the concentrations of reactants and products.
2. At dynamic equilibrium, what happens to the concentrations of reactants and products?
A.
They remain constant
B.
They become zero
C.
They continuously increase
D.
They continuously decrease
Correct Answer:
They remain constant
Explanation:
The concentrations remain constant because the forward reaction forms products at the same rate as the reverse reaction forms reactants.
3. Which statement about a system at dynamic equilibrium is correct?
A.
The reaction has stopped completely
B.
The reactants and products must be present in equal amounts
C.
Both forward and reverse reactions are still occurring
D.
Only products are present
Correct Answer:
Both forward and reverse reactions are still occurring
Explanation:
Dynamic equilibrium is not static. Both the forward and reverse reactions continue, but their rates are equal.
4. Dynamic equilibrium can be established only in a:
A.
Closed system
B.
System containing only solids
C.
System where no reaction occurs
D.
System containing only products
Correct Answer:
Closed system
Explanation:
A closed system does not allow reactants or products to escape, allowing the forward and reverse reactions to continue until their rates become equal.
5. For the reaction H2(g) + I2(g) ⇌ 2HI(g), what is true at equilibrium?
A.
The concentration of H2 must equal the concentration of HI
B.
The forward and reverse reaction rates are equal
C.
The reaction stops completely
D.
All H2 and I2 are converted into HI
Correct Answer:
The forward and reverse reaction rates are equal
Explanation:
At dynamic equilibrium, the forward formation of HI and the reverse decomposition of HI occur at equal rates.
6. Which change indicates that a reversible reaction has reached dynamic equilibrium?
A.
The color or concentration becomes constant
B.
The reactants disappear instantly
C.
The products disappear completely
D.
The temperature always becomes zero
Correct Answer:
The color or concentration becomes constant
Explanation:
When the forward and reverse reaction rates become equal, observable properties such as concentration or color remain constant.
7. At dynamic equilibrium, the rate of the forward reaction is:
A.
Greater than the rate of the reverse reaction
B.
Less than the rate of the reverse reaction
C.
Equal to the rate of the reverse reaction
D.
Always zero
Correct Answer:
Equal to the rate of the reverse reaction
Explanation:
Equality of the forward and reverse reaction rates is the defining feature of dynamic equilibrium.
8. Why is chemical equilibrium called dynamic?
A.
Because the reaction mixture moves physically
B.
Because both forward and reverse reactions continue
C.
Because the reaction occurs only once
D.
Because the reactants are continuously removed
Correct Answer:
Because both forward and reverse reactions continue
Explanation:
The term dynamic shows that molecular-level reactions continue even though the overall concentrations remain constant.
9. Which condition is necessary for a reversible reaction to maintain dynamic equilibrium?
A.
The forward reaction must stop
B.
The reverse reaction must stop
C.
The system must allow both reactions to occur
D.
There must be no products in the system
Correct Answer:
The system must allow both reactions to occur
Explanation:
Dynamic equilibrium requires continuous occurrence of both the forward and reverse reactions in the system.
10. At dynamic equilibrium, which statement about macroscopic properties is correct?
A.
They change rapidly with time
B.
They remain constant with time
C.
They become exactly zero
D.
They always become equal for reactants and products
Correct Answer:
They remain constant with time
Explanation:
Although reactions continue microscopically, equal forward and reverse rates make observable properties remain constant over time.