Water to Milk and Back Again
Chemical reaction involving precipitates.
How many of you like to drink water for dinner? How many of you like to drink milk? Well I like to drink both so lets see if I could turn this water into milk and then turn it back into water again.
1. Dissolve 3 g solid anhydrous calcium chloride in 500 mL if distilled water.
2. In a 2nd beaker place 10 mL of ammonium oxalate.
3. In a 3rd beaker place 45 mL of 6 M nitric acid.
4. Pour the calcium chloride solution into the beaker with ammonium oxalate (Milk)
5. Pour the "milk" into the 3rd beaker with nitric acid (water).
When the calcium chloride solution is mixed with the ammonium oxalate a white precipitate of calcium oxalate is produced (milk). When you combine this with nitric acid it turns clear again because the calcium oxalate dissolves.
CaCl2 + (NH4)2(C2 O4 ) ----> CaC2 O4 + NH4 Cl
Ca (C2O4) + HNO3 ----> Ca(NO3 )2 + H2(C2O4)
In these chemical reactions the starting chemicals switch partners. The positive and negative ionis switch partners.
Reference: Chem, P, Entertaining and Educational Demonstrations, Chemical Elements Publishing Company, 1974, p. 13