Give two requirements for vapour phase refining.
Two requirements for vapour phase refining are
(i) The metal should form a volatile compound with an available reagent.
(ii) The volatile compound should be easily recovered by decomposition.
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 |