chemistry : class12 Molar Conductance Variation : Conductance in electrolytic solutions : Electrochemistry MCQ Questions and Answers
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Molar Conductance Variation
MCQ questions and answers.
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MCQ Questions
1. What happens to the molar conductance of an electrolyte when its solution is diluted?
A.
It generally increases
B.
It always decreases
C.
It becomes zero
D.
It remains unchanged
Correct Answer:
It generally increases
Explanation:
Molar conductance generally increases on dilution because ions move more freely and, especially for weak electrolytes, ionization increases.
2. The molar conductance of a strong electrolyte increases slightly on dilution mainly because:
A.
The number of molecules decreases
B.
Interionic attractions decrease
C.
The solvent evaporates
D.
The electrolyte becomes a nonelectrolyte
Correct Answer:
Interionic attractions decrease
Explanation:
For strong electrolytes, ions are already almost completely dissociated. Dilution reduces interionic attraction, increasing ionic mobility and hence molar conductance.
3. Which type of electrolyte shows a sharp increase in molar conductance on dilution?
A.
Weak electrolyte
B.
Strong electrolyte
C.
Nonelectrolyte
D.
Metallic conductor
Correct Answer:
Weak electrolyte
Explanation:
Dilution greatly increases the ionization of a weak electrolyte, producing more ions and causing a sharp rise in molar conductance.
4. At infinite dilution, molar conductance is represented by which symbol?
A.
K
B.
Λm
C.
Λm°
D.
R
Correct Answer:
Λm°
Explanation:
Λm° denotes the limiting molar conductance, which is the molar conductance at infinite dilution.
5. As the concentration of a strong electrolyte decreases, its molar conductance approaches:
A.
Zero
B.
Its limiting molar conductance
C.
Its resistance
D.
Its concentration value
Correct Answer:
Its limiting molar conductance
Explanation:
On dilution, the molar conductance of a strong electrolyte increases and approaches the limiting value, Λm°, at infinite dilution.
6. Which statement correctly describes the variation of molar conductance with concentration for a weak electrolyte?
A.
It decreases sharply on dilution
B.
It increases sharply on dilution
C.
It remains zero at all concentrations
D.
It remains exactly constant on dilution
Correct Answer:
It increases sharply on dilution
Explanation:
Weak electrolytes become more ionized on dilution, so their molar conductance increases sharply as concentration decreases.
7. For a strong electrolyte, the plot of molar conductance against the square root of concentration is approximately:
A.
A straight line with a positive slope
B.
A straight line with a negative slope
C.
A horizontal line at zero
D.
A vertical line
Correct Answer:
A straight line with a negative slope
Explanation:
For strong electrolytes, molar conductance decreases approximately linearly with the square root of concentration, so the plot has a negative slope.
8. Which has the highest molar conductance for the same electrolyte?
A.
A concentrated solution
B.
A dilute solution
C.
A solution at its solubility limit
D.
A solution before ionization
Correct Answer:
A dilute solution
Explanation:
Molar conductance increases as the solution is diluted, so a dilute solution has a higher molar conductance than a concentrated solution of the same electrolyte.
9. Why does molar conductance of a weak electrolyte increase significantly on dilution?
A.
Its degree of ionization increases
B.
Its ions disappear
C.
Its molar mass decreases
D.
Its solvent changes into an electrolyte
Correct Answer:
Its degree of ionization increases
Explanation:
Dilution increases the degree of ionization of a weak electrolyte, increasing the number of ions available to conduct electricity and raising molar conductance.
10. The difference between molar conductance at a given concentration and at infinite dilution is generally much greater for:
A.
Strong electrolytes
B.
Weak electrolytes
C.
Nonelectrolytes
D.
Insulators
Correct Answer:
Weak electrolytes
Explanation:
Weak electrolytes undergo substantial additional ionization on dilution, so their molar conductance changes much more before reaching the limiting value.
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