JEE Advanced · 2025 · 18 May 2025 · Paper 1 · Redox Reactions and Electrochemistry

In an electrochemical cell, dichromate ions in aqueous acidic medium are reduced to

Cr^{3 +}

. The current (in amperes) that flows through the cell for 48.25 minutes to produce 1 mole of

Cr^{3 +}

is ____.

Use: 1 Faraday

= 96500 C mol^{- 1}

Answer: 100

Solution

The balanced reduction reaction is:

Cr_{2} O_{7}^{2 -} (a q) + 6 e^{-} + 14 H^{+} (a q) \to 2 Cr^{3 +} (a q) + 7 H_{2} O (l)

For 1 mole of

Cr^{3 +}

, we need 3 moles of electrons (3 Faradays).

Using

Q = I t

\frac{I \times 48.25 \times 60}{96500} = 3

I = \frac{3 \times 96500}{48.25 \times 60} = \frac{289500}{2895} = 100 A

JEE Advanced · 2025 · 18 May 2025 · Paper 1 · Numerical answer

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