a PLAYCHEM experiment
Determining the  Empirical Formula of a HYDRATE,  XAR·YH2O
There is a.... TUTORIAL
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You will be assigned a solid UNKNOWN Hydrate and be given the Formula Weight of the anhydrous material.
You are to determine quantitatively...........
A. Per cent water in the HYDRATE
per cent water = [(weight of water)/(weight of hydrate)] 100

Mole Ratio (water:anhydrous residue)
mole ratio = moles of water/mole of anhydrous residue

  • Use a 15 cm sample tube.
  • Weigh it empty and after adding all of the  hydrate.
  • Heat both the bottom of the tube to drive the water out of the solid hydrate and the top to make sure the released water is driven completely out of the tube.
  • The tube you weigh after heating must not contain any droplets of condensed water.
  • Weigh the tube AFTER COOLING.

Did you drive off all the water from the hydrate?

Don't ask Prof. Kluiber. What does he know? Find out for yourself!
To find out.....

  • Reheat the the tube. Watch for any water being given off. There should not be any!
  • Cool and reweigh.
  • If the two weights are the same,  ± 1-2 mg, and no water was given off, you probably dehydrated the hydrate properly.

 © R.W. Kluiber  1/23/2000