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JEE Advanced levelSingle correct optionDifficulty 3 of 3ec133

of is electrolysed between platinum electrodes with a steady current of . Take and neglect volume changes. Which statement is correct?

  1. AAfter the cathode product changes from to and the solution is then in
  2. BAfter the cathode product changes from to and the solution is then in
  3. CAfter oxygen starts to evolve at the cathode
  4. DCopper deposition continues indefinitely because is regenerated at the anode

Answer: A

Moles of , needing of electrons, i.e. , so . Up to this time the anode reaction produces , i.e. in , which is . Once is exhausted, (or water) is reduced at the cathode and evolves. Platinum anode cannot supply , so (D) is false.
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