Lecture 59 Formulas of Hydrates Ozgur Unal 1
What is the difference between the two fruits? 2 Can you find how much water was removed from the fruit?
A hydrate is a compound that has a specific number of water molecules bound to its atoms. Example: Epsom salt MgSO4.7H2O One epsom salt molecule has 7 water molecules and 1 MgSO4 formula unit. 3 In order to name hydrates we use prefixes Table 10.1 Examples: MgSO4.7H2O magnesium sulfate heptahydrate CaCl2.2H2O Calcium chloride dihydrate CuSO4.5H2O copper (II) sulfate pentahydrate Ba(OH)2.8H2O ?? Na2CO3.10H2O ??
When a hydrate is heated, water molecules are driven off leaving an anhydrous compound (without water). Check out Figure 10.17!! How can we determine the formula of a hydrate? 4 Example: A mass of 2.5 g of blue, hydrated copper sulfate (CuSO4.xH2O) is placed in a crucible and heated. After heating, 1.58 g of white anhydrous copper sulfate (CuSO4) remains. What is the formula for the hydrate? Name the hydrate. Example: An g sample of a common hydrate of cobalt (II) chloride is heated. After heating, mol of anhydrous cobalt chloride remains. What is the formula and the name of this hydrate?