Moles and Formulas 3
http://commons.wikimedia.org/wiki/File:Hydrating-copper(II)-sulfate.jpg
Formulas of Hydrated Compounds
Thursday, 10 October, 13
Hydrated Compounds
Many ionic compounds occur as “hydrates”:
copper sulfate pentahydrate
CuSO4•5H2O
http://commons.wikimedia.org/wiki/File:Copper%28II%29-sulfate-pentahydrate-sample.jpg
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Hydrated Compounds
Molecules of water are incorporated into the crystal lattice
structure of a hydrated compound.
non-hydrated ionic compound
http://www.bbc.co.uk/schools/gcsebitesize/science/add_ocr/chemicals/ioniccompoundsrev2.shtml
hydrated ionic compound
http://www.chem1.com/acad/webtext/chemeq/Eq-04.html
Forces of attraction between the ions and water molecule hold the
water molecules in position.
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Naming Hydrated Compounds
ionic compound name + prefix-hydrate
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1
6
2
7
3
8
4
12
5
1/2
Naming Hydrated Compounds
ionic compound name + prefix-hydrate
1
Thursday, 10 October, 13
mono
6
2
7
3
8
4
12
5
1/2
Naming Hydrated Compounds
ionic compound name + prefix-hydrate
Thursday, 10 October, 13
1
mono
6
2
di
7
3
8
4
12
5
1/2
Naming Hydrated Compounds
ionic compound name + prefix-hydrate
Thursday, 10 October, 13
1
mono
6
2
di
7
3
tri
8
4
12
5
1/2
Naming Hydrated Compounds
ionic compound name + prefix-hydrate
1
mono
6
2
di
7
3
tri
8
4
tetra
12
5
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1/2
Naming Hydrated Compounds
ionic compound name + prefix-hydrate
Thursday, 10 October, 13
1
mono
6
2
di
7
3
tri
8
4
tetra
12
5
penta
1/2
Naming Hydrated Compounds
ionic compound name + prefix-hydrate
Thursday, 10 October, 13
1
mono
6
2
di
7
3
tri
8
4
tetra
12
5
penta
1/2
hexa
Naming Hydrated Compounds
ionic compound name + prefix-hydrate
Thursday, 10 October, 13
1
mono
6
hexa
2
di
7
hepta
3
tri
8
4
tetra
12
5
penta
1/2
Naming Hydrated Compounds
ionic compound name + prefix-hydrate
Thursday, 10 October, 13
1
mono
6
hexa
2
di
7
hepta
3
tri
8
octa
4
tetra
12
5
penta
1/2
Naming Hydrated Compounds
ionic compound name + prefix-hydrate
Thursday, 10 October, 13
#
prefix
#
prefix
1
mono
6
hexa
2
di
7
hepta
3
tri
8
octa
4
tetra
12
dodeca
5
penta
1/2
hemi
Hydrated Compounds
There are a fixed number of water molecules
per “formula unit”.
chemical formula
name
ratio of water to
formula unit
CuSO4•5H2O
copper (II) sulfate pentahydrate
5:1
MgSO4•7H2O
magnesium sulfate heptahydrate
7:1
CaCl2•2H2O
calcium chloride dihydrate
2:1
Ba(OH)2•8H2O
barium hydroxide octahydrate
8:1
MgSO4
anhydrous magnesium sulfate
n/a
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Experimental Determination
http://www.sciencephoto.com/media/4740/enlarge
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Experimental Determination
http://group.chem.iastate.edu/Greenbowe/sections/projectfolder/empiricalformulatutorial2.htm
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Experimental Determination
Data
initial mass of hydrate before heating =
final mass of anhydrous compound after heating =
Calculations
1. mass of H2O released =
2. moles of H2O released =
3. moles of anhydrous compound =
4. find ratio of moles of water to moles of anhydrous compound
ratio = moles H2O / moles anhydrous compound =
5. formula and name:
Thursday, 10 October, 13