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GATE 2021 CY – Question 44

Physical Chemistry · Electrochemistry: Standard electrode potential and electrochemical cells. Nernst Equation and its application, relationship between electrode potential and thermodynamic quantities, Potentiometric and conductometric titrations. Ionic mobility and conductivity. Kohlrausch’s law, Debye-Hückel limiting law. Debye-Hückel- Onsager equation. · 2 marks · Multiple choice

In a cell, $Ag^+$ from $AgNO_3$ is reduced at the cathode and Cu oxidizes to $Cu^{2+}$ at the anode. A 0.7 A current flows for 10 min. The masses of Ag deposited and Cu dissolved, respectively, are ______ g. $F=96485$ C/mol; atomic weights Ag 107.9, Cu 63.55.

  1. 0.469 and 0.138
  2. 0.235 and 0.138
  3. 0.469 and 0.069
  4. 0.235 and 0.069

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Correct answer: (A) 0.469 and 0.138

Explanation

The charge is 0.7×600=420 C, corresponding to 420/96485 mol electrons. Ag+ requires one electron, so mAg=(420/96485)×107.9=0.4697 g. Cu gives two electrons per atom, so mCu=(420/(2×96485))×63.55=0.1383 g. The matching pair is **0.469 and 0.138 g, A**.