6
MCQ (Single Correct Answer)
In the extraction of copper from its sulphide ore, the metal is formed by the reduction of $\mathrm{Cu}_2 \mathrm{O}$ with
A
FeS
B
CO
C
$\mathrm{Cu}_2 \mathrm{S}$
D
$\mathrm{SO}_2$
7
MCQ (Single Correct Answer)
Brine is electrolysed by using inert electrodes. The reaction at anode is ............... .
A
$\mathrm{Cl}^{-}(a q) \rightarrow \frac{1}{2} \mathrm{Cl}_2(g)+e^{-}$; $\qquad E_{\text {Cell }}^{\mathrm{s}}=1.36 \mathrm{~V}$
B
$2 \mathrm{H}_2 \mathrm{O}(l) \rightarrow \mathrm{O}_2(g)+4 \mathrm{H}^{+}+4 e^{-}$; $\qquad E_{\text {Cell }}^{\mathrm{s}}=1.23 \mathrm{~V}$
C
$\mathrm{Na}^{+}(a q)+e^{-} \rightarrow \mathrm{Na}(\mathrm{s})$; $\qquad E_{\text {Cell }}^{\mathrm{s}}=2.71 \mathrm{~V}$
D
$\mathrm{H}^{+}(\mathrm{aq})+\mathrm{e}^{-} \rightarrow \frac{1}{2} \mathrm{H}_2(\mathrm{~g})$; $\qquad E_{\text {Cell }}^{\mathrm{S}}=0.00 \mathrm{~V}$
8
MCQ (Single Correct Answer)
In the metallurgy of aluminium ............. .
A
$\mathrm{Al}^{3+}$ is oxidised to $\mathrm{Al}(\mathrm{s})$.
B
graphide anode is oxidised to carbon monoxide and carbon dioxide.
C
oxidation state of oxygen changes in the reaction at anode.
D
oxidation state of oxygen changes in the overall reaction involved in the process.
9
MCQ (Single Correct Answer)
Electrolytic refining is used to purify which of the following metals?
A
Cu and Zn
B
Ge and Si
C
Zr and Ti
D
Zn and Hg
10
MCQ (Single Correct Answer)
Extraction of gold and silver involves leaching the metal with $\mathrm{CN}^{-}$ion The metal is recovered by ........... .
A
displacement of metal by some other metal from the complex ion.
B
roasting of metal complex.
C
calcination followed by roasting.
D
thermal decomposition of metal complex.