Test Index

Isolation of Elements

Section: Chemistry

Question : 4 of 22

Marks: +1, -0

A mixture of PbS and PbO undergoes self-reduction to produce $\mathrm{Pb}$ and $\mathrm{SO}_2$ .
In the extraction process of copper from copper pyrites, silica is added to produce copper silicate.
Partial oxidation of sulphide ore of copper by roasting, followed by self-reduction produces blister copper.
In cyanide process, zinc powder is utilized to precipitate gold from $\mathrm{Na}[\mathrm{Au}(\mathrm{CN})_2]$

Solution:

(a)

\mathrm{PbS}+2\mathrm{PbO}\rightarrow 3\mathrm{Pb}+\mathrm{SO}

, (self reduction)

(b) Silica is added to remove impurity of

\mathrm{Fe}

in the form of slag

\mathrm{FeSiO}_3

. Hence, this statement is wrong.

(c) Sulphide ore is partially oxidized first by roasting and then self reduction of Cu takes place to produce blister copper.

\mathrm{Cu}_2\mathrm{S}+\frac{3}{2}\mathrm{O}_2\rightarrow \mathrm{Cu}_2\mathrm{O}+\mathrm{SO}_2\uparrow

\mathrm{Cu}_2\mathrm{S}+2\mathrm{Cu}_2\mathrm{O}\rightarrow 6\mathrm{Cu}+\mathrm{SO}_2\uparrow

(self reduction)

The molten copper obtained is poured in to large container and allowed to coal and during cooling the dissolved

\mathrm{SO}_2

comes upto the surface and forms blisters. It is known as blister copper.

(d)

2\mathrm{Na}\left[\overset{+1}{\mathrm{Au}}(\mathrm{CN})_2\right]+\underset{\text{Reducing Agent}}{\mathrm{Zn}}\rightarrow \mathrm{Na}_2\left[\overset{+2}{\mathrm{Zn}}(\mathrm{CN})_4\right]+\overset{0}{2\mathrm{Au}}

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