Question

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

• A. A mixture of $PbS$ and $PbO$ undergoes self-reduction to produce $Pb$ and $SO_2$.
• B. In the extraction process of copper from copper pyrites, silica is added to produce copper silicate.
• C. Partial oxidation of sulphide ore of copper by roasting, followed by self-reduction produces blister copper.
• D. In cyanide process, zine powder is utilized to precipitate gold from $Na \left[ Au ( CN )_{2}\right]$.

Answer 1

Answer: (A), (C), (D)

(A) $PbS +2 PbO \xrightarrow{\text { self reduction }}3 Pb + SO _{2} \uparrow$
So option (A) is correct.
(B) In the extraction $Cu$ from copper pyrite $CuFeS _{2}$
$SiO _{2}$ is added to remove $FeO$ as slag $FeSiO _{3}$.
So option (B) is wrong.
(C) $\underset{\text { concentrated ore }}{ CuF e S _{2}} \xrightarrow{\text { roasting }} \underbrace{ Cu _{2} S + FeS }_{\text {(matte) }}+ SO _{2}$
$FeS + O _{2} \longrightarrow FeO + SO _{2}$
$Cu _{2} S + O _{2} \longrightarrow Cu _{2} O + SO _{2}$
$Cu _{2} S +2 Cu _{2} O \longrightarrow \underset{\text { (Bister copper) }}{6 Cu }+ SO _{2}$
So, option (C) is correct.
(D) $Zn +2 Na \left[ Au ( CN )_{2}\right] \rightarrow Na _{2}\left[ Zn ( CN )_{4}\right]+2 Au \downarrow$
So, option (D) is correct.