Chemistry
Formula of a Hydrate Laboratory
Mr. Fedell
Name __________________
Some chemicals have molecules of water incorporated into their chemical structure. Two
examples of this are Magnesium chlorate and Magnesium perchlorate. Each of these molecules
has 6 waters attached. The resulting formulas are:
Mg(ClO3)2.6H2O
and
Mg(ClO4)2.6H2O ( please note – the “dot” in between the
chemical and the water is not the sign for multiplication)
As a result, when the gram molecular mass of these compounds without water is calculated, the
masses are ______________and _______________ respectively.
As a result, when the gram molecular mass of these compounds with water is calculated, the
masses are ______________and _______________ respectively.
As a result, the % by mass of water for these compounds is ____________and
_______________respectively.
The purpose of this lab is for you to determine the empirical formula of a hydrated
compound – that is, you need to determine how many waters are attached to a chemical
compound.
Procedure:
1. Obtain a clean, dry crucible and cover.
2. Heat the crucible with cover on a clay triangle supported by an iron ring with a
Bunsen burner for two to three minutes. Start by heating gently. That means starting
the Bunsen burner in the closed position, opening it until you get a blue flame, and
then gently running it under the crucible to slowly warm it. After a minute of gentle
heating, you may move the burner so that the blue flame within the flame has its edge
touching the bottom of the crucible. When finished, use tongs to carefully remove
the crucible from the clay triangle on to an asbestos pad and transport the crucible
and cover to the cooling plate in front of the fan. Make sure to note what letter and
number correspond to your section on the cooling plate. Also make sure that you do
not touch the hot crucible and lid with the tape on the cooling plate.
3. When the crucible is cool (wait 5 minutes), carefully transfer to a balance and obtain
the mass. Record the mass in a data table of your own creation.
4. While the crucible and cover are still on the balance, fill the crucible one fourth to
one third full with a hydrated compound. Replace the cover and remass.
5. Place the crucible back on the clay triangle. Replace the lid, but leave it slightly ajar
and heat gently for one minute, then increase the heat until the crucible bottom is a
dull red color. Heat at this temperature for three or four minutes.
6. Allow the crucible to cool on the cooling tray for five minutes. Remass and record in
your data table.
7. Repeat steps five and six. If your results for mass do not agree within 0.02 grams,
check with your teacher.
Lab Report Requirements: On the back of this paper:
Show a data table, show the calculations that you performed in order to find the empirical
formula of the hydrate, and circle your final answer for the empirical formula of the hydrate.