Question

Which of the following processes is used in extractive metallurgy of magnesium?
A) Fused salt electrolysis
B) Self reduction
C) Aqueous salt electrolysis
D) Thermite reduction

Answer 1

We must have to know that magnesium is a highly electropositive element. It belongs to group II i.e. alkaline earth metals and it is an s block element. Electrolysis is performed when an element is highly electropositive. The best way to purify the compounds of ionic bonds is to obtain the metal by electrolysis.

Complete answer:
The process involves reducing molten magnesium oxide slag by ferrosilicon under low gas pressure at a temperature of about $2500F$ ().The metallic magnesium, formed in the process, evaporates and then condensates away from the hot region. The condensed magnesium, having purity of$99.95\%$is then melted and cast. The first stage of the process is a preparation of magnesium chloride feed which is followed by the electrolytic dissociation of magnesium chloride. Industrial cell feeds consist of a mixture of dehydrated magnesium chloride, partly dehydrated magnesium chloride or dehydrated carnallite. Dehydrated magnesium chloride is prepared by one of two methods: Chlorination of magnesium oxide or dehydration of magnesium chloride brine. The electrolytic cell consists of a brick-lined vessel, divided into anode and cathode compartments by a semi-wall. Air- or water-cooled Graphite plate anode and steel cathode are submerged in electrolyte composed of alkaline chlorides with addition of magnesium chloride.

Thus the correct option for this question is option A) i.e. fused salt electrolysis.

Note:
The operating temperature is $1260^\circ F$ to $1380^\circ F$ ($680^\circ C$ to $750^\circ C$).Magnesium chloride decomposes in the electrolytic cell according to the reaction:
$MgC{l_2} \to Mg + C{l_2}_{\left( g \right)}$
Metallic magnesium is formed at the cathode. It floats up (it is lighter than electrolyte) collecting in the cathode compartment. Chlorine, which is a by-product of the process, is collected in the anode compartment.