JEE Advanced · Chemistry · 17. Electrochemistry

In an electrochemicalcell, dichromate ions in aqueous acidic medium are reduced to \(\mathrm{Cr}^{3+}\). The current (in amperes) that flows through the cell for 48.25 minutes to produce 1 mole of \(\mathrm{Cr}^{3+}\) is _____ .
Use: 1 Faraday \(=96500 \mathrm{C} \mathrm{mol}^{-1}\)

A 100
B 200
C 300
D 400

Verified Solution

Answer & Solution

Correct Answer

(A) 100

Step-by-step Solution

Detailed explanation

For reduction of dichromate, balanced reaction is :
\(\mathrm{Cr}_2 \mathrm{O}_7^{-2}(\mathrm{aq})+6 \mathrm{e}^{-}+14 \mathrm{H}^{+}(\mathrm{aq}) \rightarrow 2 \mathrm{Cr}^{3+}(\mathrm{aq})\) \(+~7 \mathrm{H}_2 \mathrm{O}(\mathrm{l})\)
\(\qquad \qquad \qquad3 Mole\) \(\qquad \qquad \qquad \qquad 1 Mole\)
Number of Farads required \(=3 \mathrm{~mol}\)
Let current \(=\mathrm{I}\) amperes
\(\begin{aligned}
& \Rightarrow \frac{I \times 48.25 \times 60}{96500}=3 \\
& I=100 \mathrm{~A}
\end{aligned}\)

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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In an electrochemicalcell, dichromate ions in aqueous acidic medium are reduced to \(\mathrm{Cr}^{3+}\). The current (in amperes) that flows through the cell for 48.25 minutes to produce 1 mole of \(\mathrm{Cr}^{3+}\) is _____ .Use: 1 Faraday \(=96500 \mathrm{C} \mathrm{mol}^{-1}\)

Step-by-step Solution

In an electrochemicalcell, dichromate ions in aqueous acidic medium are reduced to \(\mathrm{Cr}^{3+}\). The current (in amperes) that flows through the cell for 48.25 minutes to produce 1 mole of \(\mathrm{Cr}^{3+}\) is _____ .
Use: 1 Faraday \(=96500 \mathrm{C} \mathrm{mol}^{-1}\)