Hon. Chemistry Formula of a Hydrate Lab (Chapter 10) 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 formula mass of these compounds without water is calculated, the masses are ______and ______respectively.
As a result, when the gram formula 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.