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Electrochemistry

Short Answer Type

11. Suggest a list of metals that are extracted electrolytically.

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12. Consider the reaction: Cr₂O₇^2– + 14H⁺ + 6e- → 2Cr³⁺ + 8H₂O
What is the quantity of electricity in coulombs needed to reduce 1 mol of Cr₂O₇^2-?

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13.

Write the chemistry of recharging the lead storage battery, highlighting all the materials that are involved during recharging.

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14. Suggest two materials other than hydrogen that can be used as fuels in fuel cells.

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Long Answer Type

15. Explain how rusting of iron is envisaged as setting up of an electrochemical cell.

At a particular spot of an object made of iron oxidation takes place and that spot behaves as an anode.
At anode:

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Electrons released at anode spot moves through the metal and go to another spot on the metal and reduce oxygen in presence of H⁺ (which is believed to be available from H₂CO₃formed due to dissolution of carbondioxide from air into water. Hydrogen ion in water may also be available due to dissolution of other acidic oxides from the atmosphere). This spot behaves as a cathode with the reaction.

The ferrous ions are further oxidized by atmospheric oxygen to ferric ions which come out as rust in the form of hydrated ferric oxide (Fe₂O₃x H₂O).

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