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प्रश्न
Write the chemical reactions involved in the extraction of gold by cyanide process. Also give the role of zinc in the extraction.
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उत्तर
\[\ce{4Au(s) + 8CN^{-} (aq) + 2H2O (aq) + O2(g) -> 4[Au(CN)2]^{-} (aq) + 4OH^{-} (aq)}\]
\[\ce{2[Au(CN)2]^{-} (aq) + Zn(s) -> 2Au(s) + [Zn(CN)4]^{2-} (aq)}\]
Zinc places the role of a reducing agent. It reduces \[\ce{Au+}\] to pure \[\ce{Au}\].
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| List - I | List - II | ||
| (One) | (Composition) | ||
| (A) | Siderite | (I) | FeCO3 |
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| (C) | Sphalerite | (III) | ZnS |
| (D) | Calamine | (IV) | ZnCO3 |
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