LAB - PERCENT WATER IN A HYDRATE
NAME_______________________
Purpose: to find the percent water in a hydrate crystal
Equipment: evaporating dish, ring stand, iron ring, wire gauze, bunsen burner, balance, microspatula, crucible tongs
Materials: copper sulfate hydrate ( CuSO4
 xH2O )
Procedure:
1. Heat the empty dish strongly for 3 minutes to drive off any residual water. Let the dish cool on the base of the
ring stand for 5 minutes. Record the mass of the dish.
2. Measure out approximately 2 g of crystals into the dish. Record the mass of the dish and the crystals.
What is the appearance of the crystals?
3. Place the dish on the gauze, and begin heating the dish GENTLY with the bunsen burner. Gradually increase
the intensity of the heating process. What do you see happening?
4. Continue heating strongly until the reaction is complete. If necessary, use the microspatula to break up the
larger crystals. Make sure no solid sticks to the spatula.
5. Once the reaction is complete, remove the heat and let the dish cool on the base of the ring stand for about
1-2 minutes. Why is the cooling time so short here?
6. Record the mass of the dish and residue. Has a chemical change occurred?
Data:
a. mass of the evaporating dish
___________ g
b. mass of the dish + crystals (copper sulfate hydrate)
___________ g
c. mass of the dish + residue (anhydrous copper sulfate)
___________ g
Calculations:
1. Find the mass of hydrate crystals (b - a).
2. Find the mass of water lost (b - c).
3. Find the percent water in the hydrate:
Percent Wa ter 
#2 x100%
(#1)
4. Find the percent error of your value. The expected value is 36.0%.
Percent Error 
observed value - expected value  x100%
(expected value )
LAB - PERCENT WATER IN A HYDRATE
NAME_______________________
Conclusion:
1. List any possible error sources which would account for your error finding.
2. Why is it important to get the mass of the dish + anhydrous copper sulfate so soon after the heating?
3. Does this violate the Law of Conservation of mass? Explain your answer.
Extra Credit. Knowing the formula for this hydrate is
CuSO4  xH2O , what is x?