Given the amount of one reactant, students must use stoichiometry to find the ideal amount of the second reagent to use to create purple fireworks. The teacher ignites each groups' fireworks. Ideal mixture create little or no ash. Student assignment sheet with directions (and different initial amounts) plus teacher information and sample answers are included. This is an exciting and engaging activity that can be used as a stoichiometry quiz.
Stoichiometry, limiting reactant, laboratory measures
With one balance per table (two groups), the calculations should take about 10 minutes, the measures another 10 minutes. Ideally, students should be prepared to deliver their mixture to the teacher within 20 minutes. In practice, many students will take longer, particularly if the formula for potassium chlorate is not given and students are not familiar enough with ionic nomenclature.
The teacher will need about one minute per group to announce the group's mixture, ignite it, and wait for student responses. So if there are 15 groups, the teacher should allow about 15 minutes to ignite all the mixtures.
Student materials:
- 1 - 100 mL beaker
- 1 - 250 mL beaker
- Vial of potassium chlorate (KClO3)
- Vial of sugar (C12H22O11)
- Stirring rod
- Wax pencil
- Centigram balance (ideally one for each lab table).
- goggles
Teacher Materials:
- Fireproof board
- Bunsen burner (with long hose)
This experiment is best done in groups of two. Students should have learned how to do stoichiometry problems, be experienced in using a balance, and be able to follow basic directions.
For this lab quiz students are given a specified amount of one reactant (the limiting reactant), and must complete the correct stoichiometry calculation to determine the ideal amount of the other reactant. They are instructed to show all their work.
In a fume hood, the teacher ignites each groups' mixture. Ideally, there are purple flames and sparks and very little white "ash." An excess of sugar results in production of carbon "worms." And excess of potassium chlorate does not burn well and is difficult to ignite.
See the student lab sheet.
See the student lab sheet.
Each table (two groups) needs one balance and one vial of each reagent plus a 100 mL and a 250 mL beaker for each group (two of each beaker). It is convenient to have all the student materials placed in a tub or basket. Each table also should have a centigram balance, if possible. If more than two groups must share a balance, the lab quiz may take more time than is available.
David P. Licata, Pacifica High School, Garden Grove, CA (retired)
