Q.(a)

(a) A mineral is any natural metal compound; only the subset that is economically extractable is an 'ore' — and in copper smelting, silica is added as a flux to remove the iron-oxide gangue as slag. (b) Boric acid has antiseptic/industrial uses, and silicates are the $SiO_4$-tetrahedron-based mineral family.

(a)(i) Minerals vs. ores: A mineral is any naturally occurring inorganic substance, of a fairly definite chemical composition, found in the earth's crust. An ore is specifically that mineral (or mixture of minerals) from which a metal can be extracted conveniently and at a profit, using existing technology and current economics. So every ore is a mineral, but not every mineral is an ore — a mineral only becomes an ore when extraction from it is both technically feasible and commercially worthwhile (e.g. clay is a mineral of aluminium, but not an ore of it, since extraction is currently uneconomical; bauxite, by contrast, is both a mineral and the ore of aluminium).

(a)(ii) Role of silica in copper extraction: During the roasting/smelting of copper ores such as copper pyrites ($CuFeS_2$), the iron present is oxidised to iron(II) oxide ($FeO$) as an unwanted gangue-derived impurity. Silica ($SiO_2$) is deliberately added as a flux; it combines with this FeO to form a low-melting, fusible slag of iron(II) silicate: $FeO + SiO_2 \rightarrow FeSiO_3\ (\text{slag})$ Being less dense and immiscible with the molten copper matte ($Cu_2S$), this slag floats on top and is skimmed off, leaving the copper matte to be processed further (in the Bessemer converter) to blister copper.

OR (b)(i) Uses of boric acid: (1) as a mild antiseptic, in eye lotions/washes and as a mild disinfectant; (2) in the manufacture of borosilicate (heat-resistant) glass and enamels/glazes; (3) as a flux in soldering and metallurgical operations, helping to remove oxide films from metal surfaces; (4) for fireproofing wood and fabrics; (5) as a starting material for preparing other boron compounds (e.g. borax, boron nitride).

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