Chemical Concepts Demonstrated

• Effects of concentration changes
• Temperature changes
• Catalysts on the rate of reaction

Demonstration

0.005M MnO4- solution is poured in a 250-mL beaker containing a magnetic stirrer. A 0.5M solution of oxalic acid and sulfuric acid is poured into the beaker.

Observations

The solution turns burgandy in about 2.5 minutes, then changes from red to orange to amber to yellow over a period of four minutes.  The solution is colorless in 12 minutes total.

Explanation (including important chemical equations)

In order to utilize this reaction effectively, one must run two or more trials simultaneously.  There should be one that remains unaltered, and one or more that are modified with any of the following: a concentration change (more or less MnO₄^-in solution), a temperature change, or an additional catalyst (MnCl₂).   This reaction is useful for reaction rate changes because of the copious color changes and the length of time needed for the solution to become colorless without any procedural modifications.

Contributors

• Dr. George Bodner (Perdue University)