When 15.00 grams of Na2CO3 ?H2O are heated to drive off all the water of crystallization, 5.56 grams of residue remain. Find the amount of water for the hydrate.

Need what is special about water as a compound? how does water regulate climate? what drives water evaporation?   why is the water vapor fresh water when it rises from the ocean? why might freshwater in the form of snow take longer to enter the water cycle again than liquid precipitation?   what is an aquifer? what role do people play in the water cycle? plz just answer as many as you can ! thx if you !