S130 Prep Notes

Introduction

A simple demonstration of how a precipitate is evidence of a chemical reaction taking place is performed by mixing solutions of calcium chloride and sodium carbonate to form the precipitate calcium carbonate (CaCO₃).

CaCl₂(aq) + Na₂CO₃(aq) → CaCO₃(s) + 2NaCl(aq)

Short List

•   Two 500mL Florence flasks
•   1000mL tall beaker
•   Stirring rod
•   Goggle and gloves

Chemicals

•   Calcium Chloride dihydrate   CaCl₂ • 2H₂O
•   Sodium Carbonate monohydrate   Na₂CO₃ • H₂O

Prior to Lecture  (prep time ~ ? min.)

1. Dissolve 36.78g of CaCl₂ • 2H₂O in 500mL of H₂O (0.500M) [may already be prepared in carboy in M148]
2. Dissolve 31.00g of Na₂CO₃ • H₂O in 500mL of H₂O (0.500M)

To Conduct Demonstration

1. Combine solutions in the beaker or petri dish and stir.

Demo Time: ~5 minute

Safety and Disposal

Calcium Chloride is a skin irritant.  Wash your hands thoroughly after demonstration.  Waste is non-toxic and can be disposed in trash/down sink.

Edited May 2017 for new precipitation reaction - Kristin Boles