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What is hydrometallurgy? Explain with an example. |
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Answer» Solution :The process of extraction of metals by dissolving the ore in a suitable chemical reagent and the precipitation of the metal by more electropositive metal is called hydrometallurgy. For example, concentrated argentite, Ag2S is first treated with a dilute solution of NaCN to form the soluble complex, sodium dicyanoargentate (I). `Ag_2S + 4NaCN to underset(("Soluble"))underset("Sodium dicyano argentate (I)")(2Na[Ag(CN)_2]) + Na_2S` The solution is decanted off and made alkaline by adding NaOH and then treated with ZINC or ALUMINIUM to precipitate silver. `2Na[Ag(CN)_2] + Zn to underset("Silver")(2Ag) +underset("Sodium tetracyanozincate (II)")(Na_2[Zn(CN)_4])` `Na_2[Zn(CN)_4]+ 4NaOH to Na_2ZnO_2 + 4NaCN` Gold is ALSO precipitated from its complex salt solution in a similar way. `2K[Au(CN)_2] + Zn to K_2[Zn(CN)_4]+ 2Au` Metals such as Ti, Zr, Ta, etc, are also obtained by reducing their complex salts with alkali metals or Al. `K_2TiF_6 + 4K to 6KF + Ti` `K_2ZrF_6 + 2Al to 2AlF_3 + 2K + Zr` |
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