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.
11
MCQ (Single Correct Answer)
Choose the correct option of temperature at which carbon reduces Fe 0 to iron and produces CO.
A
Below temperature at point $A$
B
Approximately at the temperature corresponding to point $A$
C
Above temperature at point $A$ but below temperature at point $D$
D
Above temperature at point $A$
12
MCQ (Single Correct Answer)
Below point 'A' Fe0 can ............ .
A
be reduced by carbon monoxide only.
B
be reduced by both carbon monoxide and carbon.
C
be reduced by carbon only.
D
not be reduced by both carbon and carbon monoxide.