Question

Given below are 2 statements: Assertion and Reason. Choose the correct option.
Assertion: When Molar conductivity for a strong electrolyte is plotted versus $ \sqrt{C} \, (\text{mol/L})^{1/2} $, a straight line is obtained with intercept equal to Molar conductivity at infinite dilution for the electrolyte and slope equal to $ -A $. All electrolytes of a given type have the same $ A $ value.
Reason: At infinite dilution, strong electrolytes of the same type will have different numbers of ions due to incomplete dissociation.

• A. Assertion is correct but Reason is incorrect statement.
• B. Both Assertion and Reason are correct and Reason is the correct explanation of Assertion.
• C. Both Assertion and Reason are incorrect statements.
• D. Assertion is incorrect but Reason is correct statement.

Hint:

When analyzing conductivity plots, remember that for strong electrolytes, the number of ions at infinite dilution is the same for electrolytes of the same type, as they dissociate completely in the absence of concentration.

Answer 1

The Correct Option is A

The assertion is correct. When the molar conductivity \( \Lambda_m \) of a strong electrolyte is plotted against \( \sqrt{C} \), where \( C \) is the concentration, the resulting straight line is given by the equation: \[ \Lambda_m = \Lambda_m^\infty - A \sqrt{C} \] where \( \Lambda_m^\infty \) is the molar conductivity at infinite dilution, and \( A \) is the slope of the line. This relation is applicable to all electrolytes of a given type, and the same slope \( A \) is observed for all strong electrolytes under similar conditions, which is the correct observation. However, the reason is incorrect. At infinite dilution, strong electrolytes dissociate completely into ions, which means that their degree of dissociation is 100%. Therefore, strong electrolytes of the same type will have the same number of ions at infinite dilution. The statement that "strong electrolytes of the same type will have different numbers of ions due to incomplete dissociation" is incorrect, as they dissociate completely at infinite dilution. Thus, the assertion is correct, but the reason is incorrect.