A reaction between two white solids occurs when lead nitrate and potassium iodide are shaken forcefully producing a mixture of yellow and white solid products. The reaction occurs almost instantaneously when aqueous solutions of these compounds are mixed, precipitating yellow lead iodide.
Pb(NO3)2 + 2KI → PbI2 + 2KNO3
This demonstration makes a white precipitate by mixing equal amounts of silver nitrate and potassium chloride.
AgNO3 (aq) + KCl (aq) → KNO3 (aq) + AgCl (s)
The reaction of sodium thiosulfate and hydrochloric acid produces colloidal sulfur which clouds the solution. As the sulfur concentration increases, shorter wavelengths are scattered and longer ones pass through, this causes an increase of reddish color to appear on the overhead.
Na2S2O3 + HCl → 2NaCl + SO2 + S + H2O
This demo shows how a precipitation reaction works. The precipitate formed is a common ingredient in chalk.
CaCl2 (aq) + Na2CO3 (aq) → NaCl (aq) + CaCO3 (s)