3
MCQ (Single Correct Answer)
Which of the following reactions is an example of autoreduction?
A
$\mathrm{Fe}_3 \mathrm{O}_4+4 \mathrm{CO} \longrightarrow 3 \mathrm{Fe}+4 \mathrm{CO}_2$
B
$\mathrm{Cu}_2 \mathrm{O}+\mathrm{C} \longrightarrow 2 \mathrm{Cu}+\mathrm{CO}$
C
$\mathrm{Cu}^{2+}(\mathrm{aq})+\mathrm{Fe}(\mathrm{s}) \longrightarrow \mathrm{Cu}(\mathrm{s})+\mathrm{Fe}^{2+}(\mathrm{aq})$
D
$\mathrm{Cu}_2 \mathrm{O}+\frac{1}{2} \mathrm{Cu}_2 \mathrm{~S} \longrightarrow 3 \mathrm{Cu}+\frac{1}{2} \mathrm{SO}_2$
4
MCQ (Single Correct Answer)
A number of elements are available in earth's crust but most abundant elements are ............. .
A
Al and Fe
B
Al and Cu
C
Fe and Cu
D
Cu and Ag
5
MCQ (Single Correct Answer)
Zone refining is based on the principle that ............ .
A
impurities of low boiling metals can be separated by distillation.
B
impurities are more soluble in molten metal than in solid metal.
C
different components of a mixture are differently adsorbed on an adsorbent.
D
vapours of volatile compound can be decomposed in pure metal.
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
$\mathrm{H}^{+}(\mathrm{aq})+\mathrm{e}^{-} \rightarrow \frac{1}{2} \mathrm{H}_2(\mathrm{~g})$; $\qquad E_{\text {Cell }}^{\mathrm{S}}=0.00 \mathrm{~V}$