1. What is meant by chemical equilibrium in a reversible reaction?
A.
The reaction has completely stopped
B.
The forward and reverse reaction rates are equal
C.
Only the forward reaction is occurring
D.
Only the reverse reaction is occurring
Correct Answer:
The forward and reverse reaction rates are equal
Explanation:
At chemical equilibrium, the forward and reverse reactions continue, but their rates become equal.
2. Chemical equilibrium is described as dynamic because:
A.
The reactants disappear completely
B.
The products are continuously removed
C.
Both forward and reverse reactions continue
D.
The reaction takes place only once
Correct Answer:
Both forward and reverse reactions continue
Explanation:
Equilibrium is dynamic because both reactions continue simultaneously even though there is no net change in composition.
3. At equilibrium, the concentrations of reactants and products:
A.
Become equal
B.
Remain constant with time
C.
Become zero
D.
Change continuously in one direction
Correct Answer:
Remain constant with time
Explanation:
At equilibrium, the concentrations remain constant because the forward and reverse reaction rates are equal.
4. For a chemical reaction to attain equilibrium, it must generally occur in a:
A.
Closed system
B.
Vacuum only
C.
System containing only products
D.
System with continuous removal of reactants
Correct Answer:
Closed system
Explanation:
A closed system prevents the loss of reactants or products, allowing a reversible reaction to reach equilibrium.
5. Which statement is true at chemical equilibrium?
A.
The amount of reactants is always equal to the amount of products
B.
The forward reaction stops completely
C.
The forward and reverse reactions occur at equal rates
D.
Only products are present
Correct Answer:
The forward and reverse reactions occur at equal rates
Explanation:
Equal forward and reverse reaction rates are the main characteristic of chemical equilibrium.
6. Which property remains constant when a system reaches chemical equilibrium?
A.
The rate of the forward reaction alone
B.
The concentration of each species
C.
The amount of energy supplied from outside
D.
The number of collisions only in the forward direction
Correct Answer:
The concentration of each species
Explanation:
At equilibrium, the concentrations of reactants and products remain constant, although the reactions continue.
7. In a reversible reaction at equilibrium, the reactants and products are:
A.
Present in fixed concentrations
B.
Always present in equal amounts
C.
Completely absent
D.
Changing rapidly in concentration
Correct Answer:
Present in fixed concentrations
Explanation:
Equilibrium involves constant concentrations of both reactants and products, but these concentrations need not be equal.
8. Which observation indicates that a reversible reaction has reached equilibrium?
A.
The colour or concentration remains constant
B.
The reactants are fully consumed
C.
The products are fully consumed
D.
The temperature increases continuously
Correct Answer:
The colour or concentration remains constant
Explanation:
Constant measurable properties such as colour or concentration indicate that the system has reached equilibrium.
9. At equilibrium, the net change in the amounts of reactants and products is:
A.
Large and continuous
B.
Zero
C.
Equal to the initial amount
D.
Always negative
Correct Answer:
Zero
Explanation:
Although both reactions continue, equal rates produce no net change in the amounts of reactants and products.
10. Which statement correctly describes a system at equilibrium?
A.
The reaction has stopped at the molecular level
B.
The forward reaction is faster than the reverse reaction
C.
The reverse reaction is faster than the forward reaction
D.
The forward and reverse reactions continue at equal rates
Correct Answer:
The forward and reverse reactions continue at equal rates
Explanation:
Chemical equilibrium is a dynamic state in which the forward and reverse reactions continue at equal rates.
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