1. Determination of a Chemical Formula
Gravimetric Analysis and Percentage Composition

2. The Big Picture For example…
Hydrates are compounds that have water molecules as part of the crystal structure.
CuSO4 . 5 H2O
Copper(II) sulfate pentahydrate
For example…
Often, it is easy to remove the bound water molecules by simply heating. D
CuSO4 . 5 H2O
Copper(II) sulfate pentahydrate
CuSO H2O
Copper(II) sulfate
(anhydrous)

3. Overview Gravimetric Analysis = Analysis by Mass Part 1
Compound under study is MgSO4 . xH2O (a hydrate)
Your assignment: Determine x
Indirect determination
Part 2
Substance under study is a mixture of NaCl and MgSO4 . xH2O
Now you know x
Your assignment: Determine percentage MgSO4 . xH2O
NaCl unaffected by heat

4. List of Materials
Include Unknown Mixture ID
READ pages 21-22
If you heat something, it gets hot!!
Do not place hot crucibles on notebooks or bench top
Please, reread the previous sentence
Calculations
You must show in detail how you will treat your data for formula determination and unknown mixture—suggest selecting sample data and working through a calculation
Never ever weigh a hot crucible!
Each group member must sign and print name

5. Author Assignments This investigation, Author
2: Introduction and Conclusion
3: Discussion
1: Data/Results and Experimental
A: Introduction, Conclusion, Data/Results
B: Discussion and Experimental