Saturday, October 13, 2012

Identifying an Unknown Compound

Objective: In this experiment, you will identify an unknown, solid, white compound by
comparing the results of careful observations and tests that you make on the unknown to observations and tests made on a series of standard compounds. You will work with a team to characterize the standards.

When Jason’s great uncle Frederick passed away, his parents asked him to help out by sorting through the items that Uncle Fred had stored away in his attic. In a dusty corner behind an old chair, Jason found an antique apothecary chest with nine stoppered bottles inside. Each bottle contained a white powder, however, all the labels had fallen off of the bottles. Jason found the labels in a small pile at the bottom of the chest. Excited about his find, Jason immediately made plans to take the apothecary chest to “The Antiques Roadshow”, which was due to visit nearby Providence in three weeks, to have it appraised. He felt that it would make a more impressive showing if the labels were actually affixed to the bottles. Being a perfectionist, he wanted to put the correct labels on the correct bottles, but all of the powders looked so similar that their appearance did not provide a clue as to their identities. The names on the labels were relatively common materials that he could find in his own home or easily obtain in a pharmacy, grocery or hardware store: baking soda, aspirin, corn starch, an ingredient found in fertilizer, caffeine, chalk, caustic lime, Epsom salt and borax. He decided to perform some tests to identify each of the nine substances.
The experiment In today's experiment, you and the members of your group will perform the same tests that Jason has to carry out in order to solve his dilemma. The nine "known" compounds, or standards, will be provided for you. Work in a group of three or four people to fully characterize these standard compounds. Each student should characterize two or three standards. In addition, each student will be given a test tube that contains a solid, white compound that is one of the nine substances found in Uncle Fred's chest. You are responsible for identifying and fully characterizing this unknown compound. Record the code number of your test tube in your lab notebook.


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