If you are applying the process shown in the diagram to get pure silver from impure silver, then [figure in the original paper] (i) Between A and B, in which part will you put impure silver? [1]…

Since the original question refers to a diagram that is not provided, I will assume the process shown is the cupellation method (or a similar metallurgical process like electrolytic refining) commonly used to purify silver from its ores or impure forms. In such processes, impure silver is typically placed in a crucible (A) and heated in the presence of a flux (C) or an electrolyte to separate impurities.

Below is the model answer with a mermaid flowchart of the assumed process (cupellation/electrolytic refining) and explanations for each part.

Model Answer

(i) Between A and B, in which part will you put impure silver?

In the given process, impure silver is placed in part A (the crucible or anode in electrolytic refining).

• In cupellation, impure silver is heated in a crucible (A) while a blast of air is passed over it. Impurities (like lead, copper, or zinc) oxidize and are removed as slag, leaving behind pure silver.
• In electrolytic refining, impure silver acts as the anode (A), where oxidation occurs, and pure silver deposits at the cathode (B).

Thus, impure silver is always placed in part A.

flowchart TD
    A["Crucible/Anode (A)"] -->|"Impure Silver"| B["Pure Silver (B)"]
    A -->|"Impurities (as slag/gas)"| C["Flux/Air/Oxygen"]
    C -->|"Removes impurities"| B

(ii) What is the role of 'C' in obtaining pure silver?

The role of 'C' depends on the process:

1. In Cupellation:

   • 'C' represents air or oxygen blown over the molten impure silver in the crucible.
   • Oxygen reacts with impurities (e.g., lead, copper) to form oxides or sulfides, which are removed as slag (a molten waste product).
   • The reaction for lead (a common impurity) is: $$2\mathrm{Pb}+\mathrm{O}{}_2\to 2\mathrm{PbO}(\text{Lead oxide slag})$$
   • This leaves behind pure silver in the crucible.

2. In Electrolytic Refining:

   • 'C' could represent the electrolyte (e.g., silver nitrate solution) or flux (e.g., borax).
   • The electrolyte facilitates the electrochemical reaction:
     • At the anode (A, impure silver), oxidation occurs: $$\mathrm{Ag}\to \mathrm{Ag}{}^{+}+\mathrm{e}{}^{-}$$
     • At the cathode (B), pure silver deposits: $$\mathrm{Ag}{}^{+}+\mathrm{e}{}^{-}\to \mathrm{Ag}$$
   • Impurities either dissolve in the electrolyte or settle as anode mud.

Conclusion: In both methods, 'C' plays a crucial role in removing impurities—either by oxidation (cupellation) or electrochemical separation (electrolytic refining)—to yield pure silver.

Key Points for Full Marks

✅ Correct identification of parts (A = impure silver input, B = pure silver output). ✅ Clear explanation of 'C' (oxygen/air in cupellation, electrolyte/flux in refining). ✅ Chemical reactions (if applicable) to support the answer. ✅ Assumption stated (since the original diagram was missing).