Identifying Tests

Discussion
The purpose of this lab is to acquaint you with qualitative analysis and to improve your ability to record and use observations. Success in this lab exercise is highly dependent on your ability to take good observations and keep your glassware clean.

Procedure: Part I
Mix the eight solutions in groups of two using between 0.5 and 1.0 mL of each solution. Record your observations in a larger version of the table below. Be sure to use the same volume of each of the chemicals for each of the 28 possible combinations as some of the reactions you will observe are concentration dependent.

Turn in eight clean, dry test tubes in your 400 mL beaker to your instructor. All identifying marks should be removed from the beaker and the test tubes.


Procedure: Part II
Pick up a set of eight test tubes each containing about 7 mL of solution. These test tubes contain the same eight chemicals you used in part I above. Making sure the beaker containing the test tubes has a code number on it and that each test tube has a different number on it. Only the numbers 1 through 8 should be used. Record the code number on the beaker and include it in your lab report. (Note. One group may receive a ninth test tube. This means that one of the nine chemicals is one not tested in part I above. It will be your task to identify which of the nine solutions is the unknown.)

Mix the solutions as you did in part I above and record your observations in a second table. By comparing your observations from part I with your observations from this part you will be able to identify each of the chemicals in the eight test tubes.


Data Table
AgNO3 Ba(NO3)2 FeCl3 Na2SO4 K2CrO4 KSCN Pb(C2H3O2)2 K4Fe(CN)6
AgNO3
Ba(NO3)2
FeCl3
Na2SO4
K2CrO4
KSCN
Pb(C2H3O2)2
K4Fe(CN)6


Questions
1. Identify the solutions in each of the eight test tubes in part II. Be sure to include the code number on the beaker.
2. Write balanced equations for each of the chemical combinations in part I that resulted in a chemical reaction.

Teacher Notes:
This page has been enhanced for Netscape v2.0.
I have found that students like this lab, probably because of its "pretty colors". I feel it is a good investigation to emphasize the importance of taking good observations, keeping glassware clean, and enhancing problem solving and organizational skills. The experiment can be easily modified to use smaller amounts of chemicals if desired.

The idea for this lab came from a similar laboratory exercise I read about many years ago. I increased the number of solutions from seven in the original lab, to eight. I regret that I cannot give credit to the original author, because I have long forgotten his/her name.

 
Questions? Comments??
Revised on: 09/15/2003 at 15:33:02