Class 12th

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35. Option (i) and (ii)

In the extraction of alumina by Hall-Heroult's process, alumina is mixed with cryolite with the mixture of fluorspar \& fluoride that increases the conductivity of electrical and lowers the melting point of Al₂O₃ .

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14. Higher enthalpy of hydration provides extra stability to Cu²⁺  oxidation state than  +1 oxidation state. 

Enthalpy of hydration is described as the amount of energy released on dilution of one mole of gaseous ions.

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34. Option (i) and (iv)

Pig iron is the iron obtained from the blast that has many impurities (Mn, P, Si, etc.) and approximately 4% carbon content. When it is re-melted or cast with the help of scrap iron, then it has less carbon content i.e. 3% as compared to pig iron.

The Zr andTi are purified by the help of Arkel Method that contain the following reaction: 

Zr (s) + 2I₂   ZrI₄ ( g)  Zr Pure  (s) + 2I₂

Ti + 2I₂  TiI₄  Ti + 2I₂

Here we obtain Zr and Ti as a pure form of solid when purified using the Arkel method.

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13. 2Cu²⁺  +    4I^-  → Cu₂I₂ + I₂

When Cu²⁺  reacts with potassium iodide white precipitate of Cu₂I₂ is formed.

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12. Transition elements have the ability to involve their d-electrons along with their s-electrons in the process of bond formation. This results in formation of strong metal-metal bonds which makes their melting point high.