Chemistry · Metallurgy

JEE Advanced 2021 — Paper 1 — Question 17

The correct statement(s) related to the metal extraction processes is(are)

Option A:
A mixture of PbS and PbO undergoes self-reduction to produce Pb and SO 2 .
Correct
Option B:
In the extraction process of copper from copper pyrites, silica is added to produce copper silicate.
Option C:
Partial oxidation of sulphide ore of copper by roasting, followed by self-reduction produces blister copper.
Correct
Option D:
In cyanide process, zinc powder is utilized to precipitate gold from $\mathrm{Na}\left[\mathrm{Au}(\mathrm{CN})_{2}\right]$ .
Correct

Answer: A, C, D

Step-by-step solution

(A) $\mathrm{PbS}+2 \mathrm{PbO} \xrightarrow{\text { self reduction }} 3 \mathrm{~Pb}+\mathrm{SO}_{2} \uparrow$ So option (A) is correct.

(B) In the extraction Cu from copper pyrite $\mathrm{CuFeS}_{2}$ $\mathrm{SiO}_{2}$ is added to remove FeO as slag $\mathrm{FeSiO}_{3}$ .

So option (B) is wrong. (C) $\mathrm{CuFeS}_{\substack{\text { concentrated } \text { ore }}}^{\text {roasting }} \underbrace{\mathrm{Cu}_{2} \mathrm{~S}+\mathrm{FeS}}_{\text {(matte) }}+\mathrm{SO}_{2}$ $\mathrm{FeS}+\mathrm{O}_{2} \longrightarrow \mathrm{FeO}+\mathrm{SO}_{2}$

$\mathrm{Cu}_{2} \mathrm{~S}+\mathrm{O}_{2} \longrightarrow \mathrm{Cu}_{2} \mathrm{O}+\mathrm{SO}_{2}$

$\mathrm{Cu}_{2} \mathrm{~S}+2 \mathrm{Cu}_{2} \mathrm{O} \longrightarrow \underset{\text { (Bister copper) }}{6 \mathrm{Cu}}+\mathrm{SO}_{2}$

So, option (C) is correct. (D) $\mathrm{Zn}+2 \mathrm{Na}\left[\mathrm{Au}(\mathrm{CN})_{2}\right] \longrightarrow \mathrm{Na}_{2}\left[\mathrm{Zn}(\mathrm{CN})_{4}\right]+2 \mathrm{Au} \downarrow$ So, option (D) is correct.

Answer key and solution verified before publishing.

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Exam: JEE Advanced 2021
Paper: Paper 1
Subject: Chemistry
Chapter: Metallurgy
Topic: Reduction of Ore to Metal - All methods