Materials: milk of magnesia, magnetic stirrer, 3 M HCl, universal indicator sol'n, and a large beaker.
Procedure: Place 50 to 100 ml. of the milk of magnesia in the beaker with several drops of univ. ind. and about 200 ml of cold water. Start the stirrer and add the acid in small portions until the magnesium hydroxide dissolves.
Discussion: You can discuss the changes in pH (the pH drops after each addition of acid and then increases as more magnesium hydroxide dissolves).
The shifting equilibrium system (and Ksp factors) can also lead to interesting topics for discussion.
Teacher Notes:
This is an acid base demo presented at an A.P. workshop (I am surprised I had not seen it before). It is quite simple and the discussion can be taken in many directions.
Questions? Comments??
Contributed by Annis Hapkiewicz