Introduction:
This lab allows students to heat
an unknown hydrate, BaCl2 • X H2O, and use the data collected to calculate the empirical formula
of the hydrate. The students can either use the percent composition of the water and the barium chloride or they can use the
gram quantities of each to obtain the empirical formula.
Estimated time to complete lab:
50-60 minutes should be
plenty of time to complete the lab, clean up, and perform the necessary calculations.
Equipment Required:
For each group:
- Crucible
- Scoopula
- Bunsen burner
- Iron ring and stand
- Clay triangle
- Balance
- Crucible tongs
Safety Concerns:
- Wear safety glasses at ALL times during the lab.
- Students will be working with Bunsen burners, so all of the usual precautions for working with
Bunsen burners should be followed.
- Students can not leave an operating Bunsen burner unattended.
- Remind the students that the crucible, iron ring, and clay triangle will be HOT for a long time after the burner is
shut off. Burnt fingers are common among impatient students.
- Be sure to wash hands after using.
Clean Up Concerns:
Be sure that all equipment
is cool before putting it away. The barium chloride produced can safety be placed in a garbage can or washed down the sink
with running water.
What Can Go Wrong:
- If the students heat the crucible and contents too strongly initially, some of the salt can ‘spit’ out
of the crucible and land on the lab bench or the students’ hands – they don’t like this.
- In the calculations, the students often get confused
as to which mass belongs to the water and which belongs to the barium chloride.
Student Lab Sheet as a Word Document:
click here to download file
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