Experiment 3 - Percent Composition

Procedure:

Part A - Decomposition of Potassium Chlorate Reaction

1. Obtain a clean crucible and lid from your instructor. Inspect the crucible for cracks.
2. Use an analytical balance and determine the mass of the empty crucible.
   
   

   Record the mass of the empty crucible to four decimal places on the data sheet.

   
   
3. Record the mass of the crucible and the KClO₃ to four decimal places on the data sheet.
   
   

   Use an analytical balance and weigh approximately 2.5 +/- 0.1 grams of solid potassium chlorate (KClO3) into the crucible.

   
   
4. Place the crucible on the clay triangle and heat gently for about 8 minutes followed by strong heating for 10 minutes.
   
   

   The ring clamp should sit approximately 8 cm above the fisher burner.

   The bottom of the crucible should be red hot.

   
   
   
5. Allow the crucible to cool to room temperature inside the desicooler and weigh the crucible and the residue. Record the mass of the crucible and the residue (after 1st heating) to four decimal places on the data sheet.
   
   

   After heating, the crucible should be stored in the dessicooler to cool.

   
   
6. After weighing, place the crucible back on the clay triangle and heat strongly for about 5 minutes. Allow to cool and reweigh. Record the mass of the crucible and the residue (after re-heating) to four decimal places on the data sheet. If you have done a good job in heating, the mass of the crucible and residue after the 1st heating and the 2nd heating should not differ by more than 0.05 gram.