Class 12th

37. Option (ii) and (iii)

It is possible to separate two sulfide ores using the froth floatation process by adjusting the proportion of oil to water or by using 'depressants.' In the case of an ore containing ZnS and PbS, for example, the depressant used is NaCN.

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16. Fluorine - 1s²2s²2p⁵

Oxygen  -  1s² 2s² 2p⁶ 3s² 3p⁶ 

As we can infer from the electronic configuration, fluorine only has one unpaired electron in its 2p-orbital which can be involved in formation of only one bond and fluorine lacks d-orbital. 

While oxygen has d-orbitals in its configuration which allow the oxygen to form multiple bonds. Therefore, oxygen has greater stability to stabilise its oxidation states than fluorine. 

36. Option (i) and (iii)

A suspension of powdered ore is made with water during the froth floatation process. Collectors and froth stabilizers are added to it. Collectors (e.g., pine oils, fatty acids, xanthates, etc.) improve the non wettability of the mineral particles, while froth stabilizers (e.g., cresols, aniline) keep the froth stable 

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15. The reactions are explained as:

MnO₂ +  4HCl → MnCl₂ +  Cl₂ +  2H₂O

  (A)                                       (B)

3Cl₂ +     2NH₃ → NCl₃ +  3HCl

(excess)                          (C) 

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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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