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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.

Answer:

A secondary cell after use can be recharged by passing current through it in the opposite direction so that it can be used again.

Recharging: During charging process, hydrogen ions moves to cathode and sulphate ions to anode and the following reactions take place
At cathode:
PbSO₄ + H₂ → Pb + H₂SO₄At anode:
PbSO₄ + SO₄ + 2H₂O → PbO₂ + 2H₂SO₄
Thus, during charging active materials namely Pb cut the cathode and PbO₂ at the anode are formed. Sulphuric acid is formed and water is iconsumed. Due to this, the specific gravity of sulphuric acid increases and emf of the cell goes up to 2.2 volt.