Q.Describe the role of the following in the process mentioned.

Step 1 -- Silica in copper extraction. In extracting copper from copper pyrites, the concentrated ore is heated with silica added as an ACIDIC flux. The ferrous oxide formed on roasting is basic, so it combines with the acidic silica to form ferrous silicate slag: FeO(s) + SiO2(s) → FeSiO3(s), which is removed separately, leaving the copper-rich matte (Cu2S + FeS) to be processed further.

Step 2 -- Cryolite in aluminium extraction. In the Hall-Heroult process, alumina (from bauxite) is dissolved as a 20% solution in molten cryolite. Cryolite's role is to LOWER THE MELTING POINT of the overall mixture (along with the added CaCl2), so electrolysis can be carried out at a practically achievable temperature (above 1270 K) instead of at pure alumina's much higher melting point.

Step 3 -- Iodine in refining zirconium. In the Van-Arkel method, impure zirconium is heated with iodine at around 550 K, forming the volatile compound zirconium tetraiodide, ZrI4. Because ZrI4 is volatile while the solid impurities do not react with iodine, this step physically separates the zirconium (as a vapour, carried to a hot filament for decomposition) from its impurities. …

Identify the specific role each reagent plays in its named process -- flux/slag formation (silica), melting-point depression (cryolite), volatile-compound formation (iodine), and selective depression of an unwanted mineral ( …

• Confusing sodium cyanide's TWO different textbook roles -- as a LEACHING reagent that dissolves gold (Section 1.2.3) versus as a DEPRESSING agent that keeps ZnS out of the froth during flotation of gale …