Question

Consider the following metallurgical processes :

$\left(I\right)$ Heating impure metal with $CO$ and distilling the resulting volatile carbonyl (b.p. ${43}^0$C) and finally decomposition at ${150}^0$-${200}^0$C to get the pure metal.
$\left(II\right)$ Heating the sulphide ore in air until a part is converted to oxide and then further heating in the absence of air to let the oxide react with unchanged metal sulphide.
$\left(III\right)$ Electrolysisof the molten electrolyte containing approximately equal amounts of the metal chloride and $NaCl$ to obtain the metal.

The processes used for obtaining magnesium, nickel and copper are respectively :

• A. $\left(I\right)$, $\left(II\right)$ and $\left(III\right)$
• B. $\left(II\right)$, $\left(III\right)$ and $\left(I\right)$
• C. $\left(III\right)$, $\left(I\right)$ and $\left(II\right)$
• D. $\left(II\right)$, $\left(I\right)$ and $\left(III\right)$

Answer 1

The correct option is C $\left(III\right)$, $\left(I\right)$ and $\left(II\right)$

(i) Impure nickel is heated with CO to obtain volatile $\left[Ni\right(CO{)}_4]$. The volatile carbonate is distilled and decomposed at ${150}^0$to ${200}^{0}C$ to obtain pure metal.

$Ni+4CO\stackrel{{50}^0}{\to }\left[Ni\right(C{O}_4]\stackrel{{230}^0}{\to }Ni+4CO\uparrow .$

(ii) The sulphide ore of copper is heated in air until a part is converted to oxide. It is then further heated in the absence of air to let the oxide react with unchanged metal sulphide.

$C{u}_{2}S+\frac{3}{2}{O}_2⟶C{u}_{2}O+S{O}_2$
$C{u}_{2}S+2C{u}_{2}O\stackrel{hightemp}{\to }6Cu+S{O}_2$

(iii) Electrolysis of the molten electrolyte containing approximately equal amounts of the magnesium chloride and NaCl gives magnesium.

$MgC{l}_2\left(s\right)\stackrel{electrolysis}{\to }M{g}^{2+}\left(l\right)+2C{l}^{-}\left(l\right)$

At cathode : $M{g}^{2+}+2e^{-}\to Mg\left(s\right)$

At anode : $2C{l}^{-}\left(l\right)\to C{l}_2\left(g\right)+2e^{-}$