TOPIC-ACTIVITY
Formula of a precipitate or stoichiometric relationship in a reaction.
In the experiment you use 0.50 molar solutions of Pb(NO3)2 and NaI to generate the precipitate.
To green this I would like to explore the use of other reagents particularly to avoid the use of a lead compound. Perhaps several options so not all students are working with the same reaction.
Try to find reactions that are more complex than a simple one to one ratio. Perhaps a one to three or two to three ratio would be nice to include along with one to two ratios.
I would also like to modify the quantitative part (Part III) to use a measurement of the precipitate height in some sort of thin tube rather than the test tubes used in step h.
It warns against using height as a precise measurement but I feel that when they graph the height of precipitate vs millimoles of reagents they can still get the proper stoichiometric
Relationship. To get a reasonable measurement with a smaller % error there needs to be a uniform tube where the narrower the I.D. the better. This may mean simply using the smallest diameter
test tube on the market or some substitute.
LEARNING OBJECTIVES
This activity would include objective topics such as stoichiometry, molarity, and types of reactions.
GREEN CHEMISTRY PRINCIPLE(S)
#2 Maximize use of materials-atom economy
#3 Avoid hazardous materials (reagents, starting materials and solvents) and products or by-products
PLAN-TRY 1st
Possibly try some copper or iron compounds.
The more colorful the better.
e-mail bpetre@sau58.org