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General Principles And Processes of Isolation Of Elements

Long Answer Type

61.

Explain: (i) Zone refining (ii) Column chromatography.

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62.

Write down the reactions taking place in different Zones in the blast furnance during the extraction of Iron.

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Short Answer Type

63.
Write chemical reactions taking place in the extraction of zinc from zinc blende.

(a) Roasting: The concentrated ore is heated with oxygen at 900°C in reverberatory furnace to convert zinc sulphide to zinc oxide. At 900°C zinc sulphate which is formed due to the oxidation of zinc sulphide also decomposes to zinc oxide.

2 Zns + 3 O_{2} \to 2 ZnO + 2 {SO}_{2} ZnS + 2 O_{2} \to {ZnSO}_{4} 2 {ZnSO}_{4} \overset{900 °}{\to} 2 ZnO + 2 {SO}_{2} + O_{2}

(b)Reduction: Zinc oxide is reduced to zinc with the help of carbon.
ZnO + C→ Zn + CO

(c) Electrolytic Refining: Zinc can be refined by the process of electrolytic refining, In this process, impure zinc is made the anode while a pure copper strip is made the cathode. The electrolyte used is an acidified solution of zinc sulphate. Electrolysis result in the transfer of zinc in pure from the anode to the cathode.

Anode: Zn → Zn²⁺ +2e^-

Cathode: Zn²⁺ +2e^- → Zn

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