chemistry : class12 Conductance Variation : Conductance in electrolytic solutions : Electrochemistry MCQ Questions and Answers
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Conductance Variation
MCQ questions and answers.
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MCQ Questions
1. What happens to the specific conductance of an electrolytic solution when it is diluted?
A.
It generally decreases
B.
It generally increases
C.
It remains exactly constant
D.
It first becomes zero and then increases
Correct Answer:
It generally decreases
Explanation:
On dilution, the number of ions present per unit volume decreases, so the specific conductance of the solution generally decreases.
2. What is the effect of dilution on the molar conductance of an electrolyte solution?
A.
It decreases
B.
It increases
C.
It remains unchanged
D.
It becomes zero
Correct Answer:
It increases
Explanation:
Molar conductance increases on dilution because ions move more freely and, in weak electrolytes, ionisation also increases.
3. The specific conductance of a solution mainly depends on the number of ions present in:
A.
One mole of solution
B.
Unit volume of solution
C.
One gram of solute
D.
The solvent only
Correct Answer:
Unit volume of solution
Explanation:
Specific conductance is related to the conductance of a solution of unit length and unit cross-sectional area, so it depends on ions present per unit volume.
4. When a strong electrolyte solution is diluted, its molar conductance increases:
A.
Suddenly due to complete ionisation
B.
Gradually due to reduced interionic interactions
C.
Only because its ions disappear
D.
Because the number of ions per unit volume increases
Correct Answer:
Gradually due to reduced interionic interactions
Explanation:
Strong electrolytes are already almost completely ionised. Dilution mainly reduces interionic attraction, allowing ions to move more freely and gradually increasing molar conductance.
5. The increase in molar conductance on dilution is much greater for a weak electrolyte because dilution:
A.
Decreases its degree of ionisation
B.
Increases its degree of ionisation
C.
Removes the solvent molecules
D.
Decreases the number of ions formed
Correct Answer:
Increases its degree of ionisation
Explanation:
Weak electrolytes ionise more extensively on dilution, producing more ions and causing a large increase in molar conductance.
6. Which quantity generally decreases when an electrolyte solution is diluted?
A.
Molar conductance
B.
Specific conductance
C.
Degree of ionisation of a weak electrolyte
D.
Freedom of movement of ions
Correct Answer:
Specific conductance
Explanation:
Dilution reduces the concentration of ions per unit volume, so specific conductance decreases.
7. At infinite dilution, the molar conductance of an electrolyte is called:
A.
Specific conductance
B.
Limiting molar conductance
C.
Resistance
D.
Cell constant
Correct Answer:
Limiting molar conductance
Explanation:
The molar conductance at infinite dilution, where ionic interactions are negligible, is called limiting molar conductance.
8. For a weak electrolyte, the graph of molar conductance against the square root of concentration is generally:
A.
A straight line with a small slope only
B.
Highly curved
C.
A horizontal line
D.
A vertical line
Correct Answer:
Highly curved
Explanation:
For weak electrolytes, dilution significantly changes ionisation, so molar conductance varies nonlinearly and the graph is generally curved.
9. Why does specific conductance decrease on dilution even though ion mobility may increase?
A.
The number of ions per unit volume decreases
B.
The solvent becomes a perfect insulator
C.
The ions become electrically neutral
D.
The electrode distance becomes zero
Correct Answer:
The number of ions per unit volume decreases
Explanation:
Although dilution can improve ionic mobility, the decrease in the number of ions per unit volume causes specific conductance to decrease.
10. Which statement correctly describes the variation of conductance quantities on dilution?
A.
Specific conductance increases and molar conductance decreases
B.
Both specific and molar conductance decrease
C.
Specific conductance decreases and molar conductance increases
D.
Both specific and molar conductance remain constant
Correct Answer:
Specific conductance decreases and molar conductance increases
Explanation:
Dilution decreases the number of ions per unit volume, lowering specific conductance, while increased ionic freedom and ionisation raise molar conductance.
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