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Which of the following statements about electrochemical conductance is/are correct?

1. The conductance of 1 cm³ (1 mL) of a solution is defined as its specific conductivity.
2. Specific conductance increases while molar conductivity decreases upon progressive dilution.
3. The limiting equivalent conductivity of a weak electrolyte cannot be determined exactly by extrapolating the plot of equivalent conductance versus sqrt(c).
4. The electrical conductance of metals arises from the movement of free electrons.

Correct answer: The limiting equivalent conductivity of a weak electrolyte cannot be determined exactly by extrapolating the plot of equivalent conductance versus sqrt(c).

Solution

Statement A is wrong (specific conductivity is conductance of 1 cm³, i.e., 1 mL — this is actually correct as written, but the standard definition refers to conductance of 1 cm³ of solution). Statement B is wrong: both specific conductance and molar conductivity increase on dilution. Statement C is correct: Kohlrausch's linear extrapolation works for strong electrolytes but not for weak ones. Statement D is correct (metallic conduction by free electrons).

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