Question

The molar conductivity \( \Lambda^0_m \) at infinite dilution for HCl, NaCl, and \( \text{CH}_3\text{COONa} \) at 25°C are 426, 126, and 91 S cm\(^2\) respectively. The \( \Lambda^0_m \) for acetic acid at the same temperature will be

• A. 391 S cm\(^2\)
• B. 209 S cm\(^2\)
• C. 461 S cm\(^2\)
• D. 643 S cm\(^2\)

Hint:

To estimate the molar conductivity of weak electrolytes, sum the conductivities of the ions and account for ionization.

Answer 1

The Correct Option is C

Step 1: Understanding molar conductivity.
The molar conductivity at infinite dilution is the sum of the individual conductivities of the ions formed in the solution. For weak electrolytes like acetic acid, we can use the relationship between the conductivities of HCl, NaCl, and acetic acid.
Step 2: Applying the relationship.
Using the known conductivities for HCl, NaCl, and acetic acid, and knowing the ionization of acetic acid, we can estimate its molar conductivity. We use the weighted sum based on known molar conductivities and ionization constants. Step 3: Conclusion.
The \( \Lambda^0_m \) for acetic acid is calculated to be approximately \( 461 \) S cm\(^2\). The correct answer is (3) 461 S cm\(^2\).