# experiemtn 5 hydrate salt

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Experiment 5 – Percent Water in a Hydrated Salt

Pre-Lab Hints

1. Note definition of deliquescent in the introduction.
2. See side notes for part A, as well as part 1 of Technique 15C (pg 27).
3. Mass of water in sample is the mass lost by heating (initial minus final).
Water % is 100 times the g of water divided by the initial g of hydrate sample.
4. a. See step A1 in the procedure.
b. A hot sample on the balance creates air currents and causes thermal expansion, both of which decrease the accuracy of the measurement.
5. Water mass is the difference between the hydrate mass and anhydrous mass.
Be sure to subtract mass of crucible and lid to obtain mass of salt samples.
Water % is 100 times the g of water divided by the g of hydrate sample.
Skip standard deviations.
6. Find mass of 7 moles of water. Then, find the formula weight of anhydrous FeSO4.
Formula weight of hydrate is the anhydrous FeSO4 mass plus the water mass.
Water % is 100% times the mass of water divided by the formula weight of hydrate.
Multiply this % times the sample mass in part b.

Procedure Notes

Do not forget to record the anhydrous salt’s name on your report sheet.
Use three different samples of the same salt for the experiment.
Be sure to clean crucible with HCl and HNO3 (~1 ml each) before firing!
Use gloves when handling the acids, and dispose of the acids in the sink.
Do not handle fired crucible with your hands at any time.
You can burn yourself and contaminate the crucible at the same time.
Use a pair of tongs for the crucible, and a pair of forceps for the lid.
Review techniques 15B and 15C (pp 27-8).
Note figures T.15c and T.15e on page 28 for firing and for heating sample.
Cool crucible only in dessicator provided. See figure T.15b on page 27.
Dispose of all solid residues in the appropriately labeled waste jar.
Skip portions involving standard deviation.
Determine n (rounded to an integer), using the equation in the calculation notes.

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