Mr. Gibson – Chemistry II – Spring 2011 w/o February 14 th The Formula for a Hydrate

Chemistry II Unit IX(e): Hydrates w/o-Feb. 14, 2011 During your lab exercise LIII-02: Crystal Formation & Crystal Lattices; You learned about the process of drawing compounds out of solution to form crystal lattices.

Chemistry II Unit IX(e): Hydrates w/o-Feb. 14, 2011 And during your lab exercise – aqueous solutions containing those cations and anions (of a given unit formula ) fell out of the solution – as crystalline solids.

Chemistry II Unit IX(e): Hydrates w/o-Feb. 14, 2011 In your Chemistry studies you will see there are times when these crystalline solids – as they form to fall out of a solution will have some of the water molecules adhere (hang on) to the ions.

Chemistry II Unit IX(e): Hydrates w/o-Feb. 14, 2011 In general… Solids, in which water molecules are trapped are called – Hydrates. For Chemists we are more specific when talking about “Hydrates”

Chemistry II Unit X: Hydrates w/o-Feb. 14, 2011 To a Chemist a “Hydrate” is a compound that has a specific number of water molecules bound to [its] atoms.

Chemistry II Unit IX(e): Hydrates w/o-Feb. 14, 2011 For example: the semi-precious gemstone “opal” (shown at the right) is the solid “silicon dioxide” (SiO 2 ) that has water molecules bound to its atoms giving rise to the unique colors in the opal stones.

Chemistry II Unit IX(e): Hydrates w/o-Feb. 14, 2011 And since, the instances of this occurring is regular and specific; Hydrates are named in a certain way and written in a certain way [as to] communicate their structure & composition.

Chemistry II Unit IX(e): Hydrates w/o-Feb. 14, 2011 Formulas for Hydrates The solid’s Unit Formula is written first. Example: the solid -- Calcium Chloride has a unit formula written [as]: CaCl 2

Chemistry II Unit IX(e): Hydrates w/o-Feb. 14, 2011 Formulas for Hydrates The solid’s Unit Formula is written first. Example: the solid -- Calcium Chloride has a unit formula written [as]: CaCl 2

Chemistry II Unit X: Hydrates w/o-Feb. 14, 2011 Formulas for Hydrates This is followed by a raised “dot” CaCl 2

Chemistry II Unit X: Hydrates w/o-Feb. 14, 2011 Formulas for Hydrates This is followed by a raised “dot” CaCl 2

Chemistry II Unit IX(e): Hydrates w/o-Feb. 14, 2011 Formulas for Hydrates The number of associated water molecules is then written after the raised “dot” CaCl 2 2H 2 O

Chemistry II Unit IX(e): Hydrates w/o-Feb. 14, 2011 Formulas for Hydrates The number of associated water molecules is then written after the raised “dot” CaCl 2 2H 2 O

Chemistry II Unit IX(e): Hydrates w/o-Feb. 14, 2011 Naming Hydrates To indicate the number of associated water molecules in a Hydrate --- a set of names has been adopted from the field of mathematics.

Chemistry II Unit IX(e): Hydrates w/o-Feb. 14, 2011 Naming Hydrates The table of names shown at the right is used to indicate the number of water molecules associated with the crystal’s unit formula. Name PrefixMolecules of Water Mono -1 Di-2 Tri-3 Tetra-4 Penta-5 Hexa-6 Hepta-7 Octa-8 Nona-9 Deca-10

Chemistry II Unit X: Hydrates w/o-Feb. 14, 2011 Naming Hydrates Using our previous calcium chloride hydrate example & this table… we can name this particular hydrate. CaCl 2 2H 2 O Name PrefixMolecules of Water Mono -1 Di-2 Tri-3 Tetra-4 Penta-5 Hexa-6 Hepta-7 Octa-8 Nona-9 Deca-10

Chemistry II Unit IX(e): Hydrates w/o-Feb. 14, 2011 Naming Hydrates Remember the “2” in front of water? This means the calcium chloride solid has two water molecules associated with its base formula unit. CaCl 2 2H 2 O Name PrefixMolecules of Water Mono -1 Di-2 Tri-3 Tetra-4 Penta-5 Hexa-6 Hepta-7 Octa-8 Nona-9 Deca-10

Chemistry II Unit IX(e): Hydrates w/o-Feb. 14, 2011 Naming Hydrates Therefore; looking at the table to the right we look for molecules of water = “2” CaCl 2 2H 2 O Name PrefixMolecules of Water Mono -1 Di-2 Tri-3 Tetra-4 Penta-5 Hexa-6 Hepta-7 Octa-8 Nona-9 Deca-10

Chemistry II Unit IX(e): Hydrates w/o-Feb. 14, 2011 Naming Hydrates We then look at the name of the prefix that goes with that number. CaCl 2 2H 2 O Name PrefixMolecules of Water Mono -1 Di-2 Tri-3 Tetra-4 Penta-5 Hexa-6 Hepta-7 Octa-8 Nona-9 Deca-10

Chemistry II Unit IX(e): Hydrates w/o-Feb. 14, 2011 Naming Hydrates And since “prefix” means “before”… The name of this hydrate would be calcium chloride di hydrate. CaCl 2 2H 2 O Name PrefixMolecules of Water Mono -1 Di-2 Tri-3 Tetra-4 Penta-5 Hexa-6 Hepta-7 Octa-8 Nona-9 Deca-10

Chemistry II Unit IX(e): Hydrates w/o-Feb. 14, 2011 Molar Masses of Hydrates And… still using our calcium chloride dihydrate example; Given your previous experience in this unit: CaCl 2 2H 2 O Name PrefixMolecules of Water Mono -1 Di-2 Tri-3 Tetra-4 Penta-5 Hexa-6 Hepta-7 Octa-8 Nona-9 Deca-10

Chemistry II Unit IX(e): Hydrates w/o-Feb. 14, 2011 Molar Masses of Hydrates CP0214: find the molar mass of this compound, and then send your answer via Schoolrack’s message board to me. Just put it in the message text as g/mol. [value = 3 pts] CaCl 2 2H 2 O Name PrefixMolecules of Water Mono -1 Di-2 Tri-3 Tetra-4 Penta-5 Hexa-6 Hepta-7 Octa-8 Nona-9 Deca-10