Mole Ratios

Ken Karp Photography

• 12 × 75 mm test tubes (10)

• test-tube rack

• marker (to label test tubes)

• 2 dropper bottles with 0.10 M solutions of calcium chloride, CaCl₂, and sodium carbonate, Na₂CO₃

1. Number five small test tubes from 1 to 5.

2. Add drops of 0.10 M CaCl₂(aq) and 0.10 M Na₂CO₃ to the test tubes as indicated in the table below.

3. Swirl each test tube gently to mix the reactants. Allow the solids to settle for about ten minutes while you complete the table and continue the analysis.

   

1. Write the balanced chemical equation for the exchange reaction of aqueous calcium chloride with aqueous sodium carbonate. Predict the ratio of moles of CaCl₂(aq) to Na₂CO₃(aq) that will produce the maximum amount of CaCO₃(s).

2. After the solids have settled, determine which tube has the most CaCO₃(s). Identify the ratio in the table that resulted in the largest volume of solid.

3. Making Sense How do the balanced chemical equations compare to your observations?

4. If You Finish Early Suppose that you mix calcium chloride, CaCl₂(aq), with sodium oleate, NaC₁₈H₃₃O₂(aq). What products do you expect? What ratio of drops would give you the largest amount of precipitate? (Note: One product is calcium oleate, commonly referred to as soap scum.)