Consider two chemical reactions (A) and (B) that take place during metallurgical process: (a) $\mathrm{ZnCO}_{3(\mathrm{~s})} \xrightarrow{\Delta} \mathrm{ZnO}_{(\mathrm{s})}+\mathrm{CO}_{2(\mathrm{~g})}$ (b) $2 \mathrm{ZnS}_{(\mathrm{~s})}+3 \mathrm{O}_{2(\mathrm{~g})} \xrightarrow{\Delta} 2 \mathrm{ZnO}_{(\mathrm{s})}+2 \mathrm{SO}_{2(\mathrm{~g})}$ The correct option of names given to them respectively is :

(A) (a) is calcination and (b) is roasting

(B) Both (a) and (b) are producing same product so both are calcination

(C) Both (a) and (b) are producing same product so both are roasting

(D) (a) is roasting and (b) is calcination

JEE Main · 2021 · 20 Jul 2021 · Shift 2 · General Principles and Processes of Isolation of Metals

Consider two chemical reactions (A) and (B) that take place during metallurgical process:
(a)

ZnCO_{3 (s)} Δ ZnO_{(s)} + CO_{2 (g)}

(b)

2 ZnS_{(s)} + 3 O_{2 (g)} Δ 2 ZnO_{(s)} + 2 SO_{2 (g)}

The correct option of names given to them respectively is :

(A)(a) is calcination and (b) is roasting✓ Correct
(B)Both (a) and (b) are producing same product so both are calcination
(C)Both (a) and (b) are producing same product so both are roasting
(D)(a) is roasting and (b) is calcination

Answer: (A)

Solution

Calcination is heating an ore below its melting point in a limited supply of air, which drives off moisture and carbon dioxide and leaves the oxide; zinc carbonate decomposing to zinc oxide and carbon dioxide needs no oxygen from outside and is of this kind. Roasting is heating an ore in a free supply of air so that the ore is itself oxidised; zinc sulphide takes up oxygen to give zinc oxide and sulphur dioxide and so is roasted. The decomposition of the zinc carbonate is calcination and the oxidation of the zinc sulphide in air is roasting.

JEE Main · 2021 · 20 Jul 2021 · Shift 2 · Single correct option

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JEE Main · 2021 · 20 Jul 2021 · Shift 2 · General Principles and Processes of Isolation of Metals

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