How will you prepare the following? Give chemical equations also.

Anhydrous ${\mathrm{MgCl}}_2$ from hydrated magnesium chloride.

Complete and balance the following equation:

$\mathrm{Mg}{\left({\mathrm{HCO}}_3\right)}_2+\mathrm{Ca}(\mathrm{OH}{)}_2⟶{\mathrm{MgCO}}_3+\_\_\_\_+{\mathrm{H}}_2\mathrm{O}$

Complete and balance the following equation:

${\mathrm{BaCO}}_3+{\mathrm{H}}_2\mathrm{O}\left(\text{ steam }\right)\stackrel{\text{ Heat }}{⟶}\dots ..+{\mathrm{CO}}_2$

Complete and balance the following equation:

${\mathrm{BeCl}}_2+{\mathrm{LiAlH}}_4⟶\dots +\mathrm{LiCl}+\dots .$

Explain the following:

Anhydrous calcium sulphate is used as drying agent.

Explain the following:

In the manufacture of $\mathrm{Mg}$ by carbon reduction of $\mathrm{MgO}$, the product is cooled in the steam of an inert gas.

Explain the following:

Why gypsum is added to cement?