The Formula for a Hydrate

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
• Na2CO310H2O ????
• CaSO42H2O ????

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.
   
3. The ending mass is the mass of the anhydrous
   compound.
4. The difference is the mass of the water.
5. Convert both masses to moles. ?
6. To find the NUMBER of water molecules in the
   hydrate
   x moles
   H2O/moles anhydrous compound

4
Calculating the Formula for a Hydrate

• Examples p.340 (63, 64)
• Practice Problems P.349 (151-154)