Question

Metallic magnesium (Mg) is prepared by

• A. displacement of Mg by iron from $MgSO_{4}$ solution
• B. electrolysis of an aqueous solution of $Mg\left(\right.NO_{3}\left(\left.\right)_{2}$
• C. electrolysis of molten $MgCl_{2}$
• D. reduction of MgO by coke

Answer 1

Answer: (C)

Metallic magnesium (Mg) is prepared by electrolysis of molten $MgCl_{2}$ . When the molten mixture of $MgCl_{2}$ , NaCl and $CaCl_{2}$ is electrolysed. Mg (s) is obtained at cathode and $Cl_{2}\left(\right.g\left.\right)$ at anode.
A. Iron cannot displace Mg from $MgSO_{4}$ solution, because Mg is more electropositive than iron.
C. In the electrolysis of $MgCl_{2}$ (aq) solution, $Mg^{2 +}$ ions are not reduced at cathode, but $\text{H}^{\oplus}$ is reduced in preference, because the electrode potential of $Mg^{2 +}$ is less than that of $\text{H}^{\oplus}$ .
D. Coke cannot reduce MgO, because Mg is a stronger reducing element than carbon.