Metallurgy and Isolation of ElementshardMCQ SINGLE⭐ Must-Do

Magnesium is commercially extracted from sea water via Dow's process, which concludes with the electMetallurgy and Isolation of Elements Chemistry Question

Question

Magnesium is commercially extracted from sea water via Dow's process, which concludes with the electrolysis of fused Carnallite. Dehydrating hydrated Carnallite ($KCl \cdot MgCl_2 \cdot 6H_2O$) in normal air leads to the formation of an unwanted basic compound ($MgO \cdot MgCl_2$) due to hydrolysis. How is this prevented industrially?

Answer: A

💡 Solution & Explanation

Heating hydrated magnesium chloride in air causes it to hydrolyze with its own water of crystallization, yielding $MgO$. To obtain pure anhydrous $MgCl_2$ suitable for fused salt electrolysis, the crystals must be heated (calcined) in an atmosphere of dry $HCl$ gas, which suppresses the hydrolysis equilibrium.

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