Kg is the abbreviation for an SI unit of mass, which is kilogram
The term hydrate would mean that the compound contains water molecules. When this compound is heated, the water molecules are lost first which means that what remains would be the dried compound. Therefore, the H2O lost from the hydrate would be 6.00g - 3.27g = 2.73 g.
I believe it's alkali metals and alkaline earth metals.
First convert the kg to g ----- 0.03kg = 30g
Then divide the mass by the volume ----- 30g ÷ 25mL = 1.2
The density is 1.2g/mL<span />