Apologia Chemistry: Empirical Formulas lab

Before I do the Can You Make 2 Grams Lab, I plan to to the Chemical Formulas lab to reinforce empirical formulas, writing formulas, solubility, and precipitates.  Here is the student worksheet for the lab.  Here is the same lab—but described as Stoichiometry and Solubility.  Here is a data chart for the lab with more questions.

This lab addresses several topics: reaction prediction, mole ratios, solubility, and precipitates.  Allow one class for the lab and another to walk the kids through all of the questions regarding their results.  The idea is for the kids to compare different ratios of drops of two reactants or reagents with the amounts of precipitates which form.  Here is how I teach this lab.

1. The reaction between ferric nitrate (iron III nitrate) and sodium hydroxide produces sodium nitrate and iron III hydroxide.
2.  Have the kids write the formulas and balance the equation.
3.  Use the Solubility Rules to determine which product is the insoluble precipitate.
4.  The reaction between cupric chloride (copper II chloride) and sodium phosphate produces sodium chloride and copper II phosphate.
5.  Have the kids write and balance this equation.
6. Use the Solubility Rules to determine the insoluble precipitate for this reaction.
7.  Now explain how to set up the test tubes and dispense the correct number of drops.
8.  After the solutions have rested for ten minutes, use rulers and measure the ratio of solid to solution in each test tube in mm.
9. Use the equations and solution: precipitate ratios to determine the chemical formula.
*****10.  Gravimetric Analysis could be performed, too.  We are NOT!!!  We are looking at ratios.  Period.