How is dihydrogen prepared in laboratory and what conditions favours the synthesis of dihydrogen by this method.

Although ${\mathrm{D}}_2\mathrm{O}$ resembles with ${\mathrm{H}}_2\mathrm{O}$ chemically yet it is a toxic substance. Explain 

How does heavy water react with ${\mathrm{Al}}_4{\mathrm{C}}_3$?

Although ${\mathrm{D}}_2\mathrm{O}$ resembles with ${\mathrm{H}}_2\mathrm{O}$ chemically yet it is a toxic substance. Explain

Can sodium bicarbonate make water hard?

Account for the following:

Ionic hydrides are non-conductor of electricity in solid state.

Account for the following:

Electron rich hydrides behaves as Lewis bases.

Account for the following: