COMEDK · Chemistry · 18. Electrochemistry

When \(0.1 \mathrm{~mol} \mathrm{~L}^{-1}\) of KCl was filled in a Conductivity cell the resistance was 80 ohms at 298 K . (Conductivity of 0.1 M KCl at 298 K is \(1.29 \mathrm{~S} \mathrm{~m}^{-1}\). The same cell when filled with an unknown electrolyte of concentration 0.025 M , had a resistance of 92 ohms. What is the Molar conductivity of the electrolyte at the given concentration?

A \(448.7 \mathrm{~S} \mathrm{~cm}^2 \mathrm{~mol}^{-1}\)
B \(220.6 \mathrm{~S} \mathrm{~cm}^2 \mathrm{~mol}^{-1}\)
C \(0.449 \mathrm{~S} \mathrm{~cm}^2 \mathrm{~mol}^{-1}\)
D \(0.2206 \mathrm{~S} \mathrm{~cm}^2 \mathrm{~mol}^{-1}\)

Verified Solution

Answer & Solution

Correct Answer

(A) \(448.7 \mathrm{~S} \mathrm{~cm}^2 \mathrm{~mol}^{-1}\)

Step-by-step Solution

Detailed explanation

The cell constant \(G^{*}\) is given by the product of conductivity \(\kappa\) and resistance \(R\). For the KCl solution, \(\kappa_{KCl} = 1.29 \text{ S m}^{-1} = 1.29 \times 10^{-2} \text{ S cm}^{-1}\).…

Apply the relevant identity from the chapter and substitute the values established in the previous step, keeping the original constraint in view.

Use the simplified expression to isolate the unknown, then plug the result back into the question setup to confirm the working is internally consistent.

Cross-check against a boundary or limiting case. Both the dimensional balance and the qualitative behaviour at the extreme should agree with the candidate answer.

Combine the steps above to identify the correct option. The remaining choices each fail at least one of the consistency, dimensional, or boundary checks.

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