JEE Advanced 2023 — Paper 1 — CHEM-I solution

JEE Advanced2023Paper 1CHEM-I

The correct statement(s) related to processes involved in the extraction of metals is(are)

A
Roasting of Malachite produces Cuprite.
B
Calcination of Calamine produces Zincite.
C
Copper pyrites is heated with silica in a reverberatory furnace to remove iron.
D
Impure silver is treated with aqueous KCN in the presence of oxygen followed by reduction with zinc metal.

Solution

(A) Roasting of Malachite. Malachite is $CuCO_{3} \cdot Cu(OH)_{2}$ . On roasting it decomposes to cupric oxide (CuO), not cuprite ( $Cu_{2} O$ ): $CuCO_{3} \cdot Cu(OH)_{2} ⟶ 2 CuO + CO_{2} + H_{2} O .$ Hence (A) is incorrect.

(B) Calcination of Calamine. Calamine is $ZnCO_{3}$ ; on calcination it gives zincite (ZnO): $ZnCO_{3} ⟶ ZnO + CO_{2} .$ Statement (B) is correct.

(C) Removal of iron from copper pyrites. Copper pyrites ( $CuFeS_{2}$ ) is roasted and then smelted in a reverberatory furnace with silica. The iron(II) oxide reacts with silica to form fusible iron silicate slag: $FeO + SiO_{2} ⟶ FeSiO_{3} .$ Statement (C) is correct.

(D) Silver refining via cyanide. In the Mac Arthur-Forrest process, silver is leached as the soluble complex $[Ag(CN)_{2}]^{-}$ in the presence of $O_{2}$ , then precipitated by reduction with zinc: $4 Ag + 8 KCN + O_{2} + 2 H_{2} O ⟶ 4 K [Ag(CN)_{2}] + 4 KOH,$ $2 [Ag(CN)_{2}]^{-} + Zn ⟶ [Zn(CN)_{4}]^{2 -} + 2 Ag .$ Statement (D) is correct.

Correct options: (B), (C), (D).

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