Zinc is extracted from its ore, zinc blende (ZnS), through the following processes:
Concentration of Ore: Zinc blende is first concentrated by the process of frost flotation. In this method, the ore is crushed and mixed with water and frothing agents. The lighter impurities are separated from the heavier zinc ore.
Roasting: The concentrated zinc ore (ZnS) is heated in the presence of oxygen. This process is called roasting, and it converts zinc sulfide into zinc oxide, releasing sulfur dioxide: \[ 2{ZnS} + 3{O}_2 \rightarrow 2{ZnO} + 2{SO}_2 \]
Reduction of Zinc Oxide: The zinc oxide obtained from roasting is then reduced to zinc metal by heating it with carbon in a furnace: \[ {ZnO} + {C} \rightarrow {Zn} + {CO} \] This reduction process takes place at a high temperature, and zinc metal is extracted.
| Case No. | Lens | Focal Length | Object Distance |
|---|---|---|---|
| 1 | \(A\) | 50 cm | 25 cm |
| 2 | B | 20 cm | 60 cm |
| 3 | C | 15 cm | 30 cm |
Samples of four metals A, B, C, and D were added one by one to the following solutions. The results obtained were tabulated as follows:
Use the table above to answer the following questions about metals A, B, C, and D:
(i) Which is the least reactive metal?
(ii) What would be observed if C is added to a solution of copper sulphate?
(iii) Arrange the metals A, B, C, and D in the order of their decreasing reactivity.
| Case No. | Lens | Focal Length | Object Distance |
|---|---|---|---|
| 1 | \(A\) | 50 cm | 25 cm |
| 2 | B | 20 cm | 60 cm |
| 3 | C | 15 cm | 30 cm |