hydrates lecture
TRANSCRIPT
Hydrate definition
A hydrate is a compound that has a specific number of water molecules bound to its atoms
Opals
Naming Hydrates
• Write the compound and the hydrate connected by a dot
Sodium carbonate decahydrate
Naming Hydrates
Analyzing a Hydrate
• The hydrate can be removed from the compound through heat
• Cobalt (II) Chloride is a pink solid that turns deep blue when heated and water is removed (anhydrous form)
Formula for a Hydrate
• 1. Determine the number of moles of water associated with one mole of hydrate– 5 g sample of Barium Chloride Hydrate (BaCl2•xH20)
– After heating, the weight of the anhydrous sample is 4.26 g
– 5 g – 4.26 g = 0.74 g H20
– Determine moles of H20 and BaCl2 ratio
Hydrate Example
• A mass of 2.50 g of blue, hydrated copper sulfate (CuS04•xH20) is placed in a crucible and heated. After heating, 1.59 g white anhydrous copper sulfate remains. What is the formula for the hydrate? Name the hydrate.
Hydrate Example Cont’d• 1. Hydrous copper sulfate is 2.50 g
• 2. Anhydrous copper sulfate is 1.59 g
• 3. 2.5 g – 1.59 g = 0.91 g of hydrate
• 4. 0.91 g water lost, 1.59 g copper sulfate
Hydrate Example Cont’d
• 5. Calculate the moles of Copper sulfate and the moles of water lost
• 6. Determine the molar ratio
• 7. Setup the formula and name it
Practice Problems-Appendix D
• A hydrate is found to have the following percent composition
– 48.18% MgS04 and 51.2% H20
– What is the formula and name for this hydrate?
MgS04•7H20 Magnesium Sulfate heptahydrate
Practice Problems-Appendix D
• If 11.75 g of the common hydrate cobalt (II) chloride is heated, 9.25 g of anhydrous cobalt chloride remains. What is the formula and name for this hydrate?
CoCl2•2H20 Cobalt (II) Chloride dihydrate
Uses of Hydrates
• Drying agents due to hygroscopic nature (absorb water from environment)
• Solar energy (Na2S04•10H20)
Questions
Thank You!
References
• http://geology.com/gemstones/opal/#precious
• Chemistry textbook