Hydrates Chemistry

Hydrates  A class of compounds containing chemically combined water. Usually, the water is loosely held and easily lost on heating. Since the water is loosely held, it will evaporate or be pulled from the air depending on the vapor pressure of the chemical. To write hydrates, use a dot: CuSO4∙5H20

Efforescent hydrates – high vapor pressure, easily evaporate Hygroscopic hydrates – low vapor pressure, take water from the air (dessicants) Deliquescent substances will actually remove enough water from the air to dissolve themselves and form a solution.

Calculate the percent by mass of water in sodium carbonate decahydrate.

Na2CO3∙10H20 2Na = 46 C = 12 180 X 100 = 62.9% 3O = 48 286 20H = 20 10O = 160 286 g Calculate % water in copper (II) sulfate pentahydrate

CuSO4∙5H2O Cu 64 90 X 100 = 36% S 32 250 4O 64 5H20 90 250 Calculate % water in calcium chloride hexahydrate

CaCl2∙6H20 Ca 40 108 X 100 = 49.5% 2Cl 70 218 6H20 108 218