1. The Formula for a Hydrate Objectives: 6.0 Solve stoichiometric problems involving relationships among the number of particles, moles, and masses of reactants and products in a chemical reaction. 6.5 Determining the empirical or molecular formula for a compound using percent composition data

2. Naming Hydrates Definition: a compound with a specific number of water molecules attached to its atoms Use prefixes to indicate the number of water molecules: “compound prefixhydrate” –Na 2 CO 3 10H 2 O = ???? –CaSO 4 2H 2 O = ????

3. Determining the Formula of a Hydrate 1.Heat a sample to drive off all the water. 2.Subtract the ending mass from the beginning mass. 1.The ending mass is the mass of the anhydrous compound. 2.The difference is the mass of the water. 3.Convert both masses to moles. 4.To find the NUMBER of water molecules in the hydrate: x = moles H 2 O/moles anhydrous compound

4. Calculating the Formula for a Hydrate Examples: p.340 (63, 64) Practice Problems: P.349 (151-154)