Example Lab Challenge: Analyzing Precipitate Reactions

Objectives:

• Give students an opportunity to watch a precipitation reaction occur.
• Give students an opportunity to predict whether a precipitation reaction will occur.
• Give students a chance to apply chemical stoichiometry to precipitation reactions.

Materials (per lab group):

• \(200\) milliliters \(0.5 \; M AgNO_3\) solution
• \(200\) milliliters \(0.5 \; M KI\) solution
• \(200\) milliliters \(0.3 \; M Ca_3(PO_4)_2\) solution
• Three funnels
• Six beakers
• Scale
• Hot Plates

The challenge presented here is as follows: you, as the teacher, are only to label the molarity of the calcium phosphate solution. The students must determine the molarity of the other two solutions by performing reactions and measuring the masses of the precipitate.

The students may perform reactions in any order, so no fixed lab procedure will be given. Students should write out every possible combination of reactants they use and predict if any reaction will occur. For the writeup, students should write up the order in which they mixed chemicals and how they isolated precipitates and any other products to measure their masses. 

Note: This lab will likely take over an hour so a reservation of two class periods or one double period is recommended. It serves as a great review lab for cumulative exams or even the AP Chemistry exam.