Write the chemical reactions involved in the extraction of gold by cyanide process. Also give the role of zinc in the extraction.
(i) $4 \mathrm{Au}(\mathrm{s})+8 \mathrm{CN}^{-}(a q)+2 \mathrm{H}_2 \mathrm{O}(a q)+\mathrm{O}_2(g) \longrightarrow 4\left[\mathrm{Au}(\mathrm{CN})_2\right]^{-}(a q)+4 \mathrm{OH}^{-}(a q)$
(ii) $2\left[\mathrm{Au}(\mathrm{CN})_2\right]^{-}(a q)+\mathrm{Zn}(\mathrm{s}) \longrightarrow 2 \mathrm{Au}(\mathrm{s})+\left[\mathrm{Zn}(\mathrm{CN})_4\right]^{2-}(a q)$
Zinc acts as a reducing agent in this reaction.
Match the items of Column I with items of Column II and assign the correct code.
| Column I | Column II | ||
|---|---|---|---|
| A. | Pendulum | 1. | Chrome steel |
| B. | Malachite | 2. | Nickel steel |
| C. | Calamine | 3. | $\mathrm{Na_3AlF_6}$ |
| D. | Cryolite | 4. | $\mathrm{CuCO_3.Cu(OH)_2}$ |
| 5. | $\mathrm{ZnCO_3}$ |
Match the items of Column I with the items of Column II and assign the correct code.
| Column I | Column II | ||
|---|---|---|---|
| A. | Coloured bands | 1. | Zone refining |
| B. | Impure metal to volatile complex | 2. | Fractional distillation |
| C. | Purification of Ge and Si | 3. | Mond's process |
| D. | Purification of mercury | 4. | Chromatography |
| 5. | Liquation |
Match items of Column I with the items of Column II and assign the correct code.
| Column I | Column II | ||
|---|---|---|---|
| A. | Cyanide process | 1. | Ultrapure Ge |
| B. | Froth floatation process | 2. | Dressing of ZnS |
| C. | Electrolytic reduction | 3. | Extraction of Al |
| D. | Zone refining | 4. | Extraction of Au |
| 5. | Purification of Ni |
Match the items of Column I with the items of Column II nd assign the correct code.
| Column I | Column II | ||
|---|---|---|---|
| A. | Sapphire | 1. | $\mathrm{Al_2O_3}$ |
| B. | Sphalerite | 2. | $\mathrm{NaCN}$ |
| C. | Depressant | 3. | $\mathrm{Co}$ |
| D. | Corundum | 4. | $\mathrm{ZnS}$ |
| 5. | $\mathrm{Fe_2O_3}$ |