chemistry : class11 Suppression of Ionization : Common ion effect : Equilibrium MCQ Questions and Answers
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Suppression of Ionization
MCQ questions and answers.
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MCQ Questions
1. What happens to the ionization of a weak acid when a salt containing its common ion is added?
A.
Its ionization increases
B.
Its ionization decreases
C.
Its ionization becomes complete
D.
Its ionization remains unchanged
Correct Answer:
Its ionization decreases
Explanation:
The added salt supplies a common ion, shifting the ionization equilibrium of the weak acid backward and suppressing its ionization.
2. Which substance suppresses the ionization of acetic acid in aqueous solution?
A.
Sodium acetate
B.
Sodium chloride
C.
Potassium nitrate
D.
Calcium sulfate
Correct Answer:
Sodium acetate
Explanation:
Sodium acetate provides acetate ions, which are common ions in the ionization equilibrium of acetic acid. Therefore, acetic acid ionization is suppressed.
3. The ionization of ammonium hydroxide is suppressed by adding which compound?
A.
Ammonium chloride
B.
Sodium chloride
C.
Potassium nitrate
D.
Calcium chloride
Correct Answer:
Ammonium chloride
Explanation:
Ammonium chloride provides NH4+ ions, which are common to the ionization equilibrium of ammonium hydroxide. This decreases its ionization.
4. For the equilibrium CH3COOH ⇌ H+ + CH3COO−, adding sodium acetate causes the equilibrium to shift in which direction?
A.
To the right
B.
To the left
C.
It stops completely
D.
It changes into a precipitation reaction
Correct Answer:
To the left
Explanation:
Sodium acetate increases the concentration of CH3COO−, a common ion. According to Le Chatelier’s principle, the equilibrium shifts left and suppresses acetic acid ionization.
5. Which ion suppresses the ionization of ammonium hydroxide?
A.
Na+
B.
Cl−
C.
NH4+
D.
NO3−
Correct Answer:
NH4+
Explanation:
NH4+ is a common ion in the equilibrium NH4OH ⇌ NH4+ + OH−. Increasing its concentration shifts the equilibrium backward and suppresses ionization.
6. What is the main reason for adding sodium acetate to acetic acid solution?
A.
To increase the ionization of acetic acid
B.
To suppress the ionization of acetic acid
C.
To convert acetic acid into a strong acid
D.
To remove acetate ions from the solution
Correct Answer:
To suppress the ionization of acetic acid
Explanation:
Sodium acetate supplies acetate ions, the common ions of acetic acid, thereby reducing the extent of acetic acid ionization.
7. The ionization of a weak electrolyte decreases when a strong electrolyte containing a common ion is added. This effect is called the:
A.
Common ion effect
B.
Neutralization effect
C.
Catalytic effect
D.
Dilution effect
Correct Answer:
Common ion effect
Explanation:
The common ion effect is the suppression of the ionization of a weak electrolyte by adding a strong electrolyte that provides one of its ions.
8. What happens to the concentration of unionized acetic acid when sodium acetate is added to its solution?
A.
It decreases
B.
It increases
C.
It becomes zero
D.
It remains exactly the same
Correct Answer:
It increases
Explanation:
Acetate ions from sodium acetate shift the equilibrium CH3COOH ⇌ H+ + CH3COO− to the left, forming more unionized acetic acid.
9. Hydrogen sulfide is a weak electrolyte. Which addition suppresses its ionization by providing H+ ions?
A.
Hydrochloric acid
B.
Sodium hydroxide
C.
Sodium chloride
D.
Potassium nitrate
Correct Answer:
Hydrochloric acid
Explanation:
Hydrochloric acid supplies H+ ions, which are common to the ionization equilibrium of hydrogen sulfide. The increased H+ concentration suppresses its ionization.
10. When ammonium chloride is added to ammonium hydroxide solution, the concentration of OH− ions generally:
A.
Increases greatly
B.
Decreases
C.
Becomes equal to the NH4+ concentration
D.
Remains unaffected
Correct Answer:
Decreases
Explanation:
NH4+ from ammonium chloride is a common ion and shifts the ammonium hydroxide ionization equilibrium backward, decreasing the concentration of OH− ions.
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