Objectives:
In this lab you are trying to see (literally, since the effects you are looking for are visible color changes), how a system at equilibrium responds to change. This is a qualitative lab. Look for general changes, rather than measureable amounts.
Warning!Long term exposure to chromium(VI) compounds is known to cause cancer in humans. While the quantities required for this lab are very small and would be very unlikely to harm you, you will not be carrying out the actual procedure. The use of chromium (VI) compounds is not allowed in most high schools, because of concerns about its carcinogenicity (Read the MSDS for potassium chromate). Because of the small amount used by students to carry out this lab, the risk to them is small; however, disposal of waste materials may pose a problem. For this reason, teachers should not allow students to carry out this procedure. |
Procedure: A set of photographs showing the various results at each step are included for reference, so that you need not actually physically handle the chemicals.