Question

The value of 'A' in the equation λ_m = λ_m° - A√C is same for the pair:

• A. NaCl and Cacl₂
• B. CaCl₂ and MgSO₄
• C. NaCl and KBr
• D. MgCl₂ and NaCl

Answer 1

The Correct Option is C

The equation given is:

\[ \lambda_m = \lambda_m^0 - A \sqrt{C} \] 

Where:

• \( \lambda_m \) is the molar conductivity.
• \( \lambda_m^0 \) is the limiting molar conductivity.
• A is a constant for the given solution.
• C is the concentration of the solution.

Explanation: 

The constant \(A\) in the equation depends on the properties of the ions in the solution. The values of \(A\) are the same for pairs of salts that have similar ionic structures and behavior. From the given options:

• NaCl and KBr both consist of monovalent ions (Na⁺, Cl⁻, K⁺, Br⁻) and thus have similar ionic conductivities, which means the constant \(A\) will be the same for both.

Thus, the pair that gives the same value of \(A\) is (C) NaCl and KBr.

Conclusion:

The correct answer is (C) NaCl and KBr.

Answer 2

The equation \( \lambda_m = \lambda_m^0 - A\sqrt{C} \) represents the relationship between the molar conductivity at infinite dilution (\( \lambda_m^0 \)) and the molar conductivity \( \lambda_m \) for a given concentration \( C \).  

The value of \( A \) is the same for pairs of electrolytes that have similar ionic sizes and structures. NaCl and KBr have similar ionic structures, making the value of \( A \) the same for both.