Gravimetric Analysis of a Lead Solution




In lecture we demonstrated that lead (II) acetate is in commercial hair dyes like Grecian Formula.  In that demonstration we precipitated it out as an insoluble sulfide.  


In the virtual lab labeled "Gravimetric Analysis" you will find 6 solutions, (A-F).  Each solution contains various unknown concentrations of lead(II).  Your task is to design and run an experiment to determine the concentration of the lead in your unknown.  This is an inquiry-based activity and you will not be given any procedural instructions.   Hopefully, you have learned enough chemistry to be able to design an experiment to answer this question.  This experiment is identical in principle to experiment 5, in which you determined the concentration of Iron(III) in an unknown solution.  The only difference is in experiment 5 you were graded entirely on your procedural techniques.  In this postlab assignment you are not graded on techniques but your ability to apply the concepts behind experiment 5 to a different unknown.


You may wish to review your solubility rules before designing this experiment.    In addition to your unknowns, the "Gravimetric Analysis Lab" contains 2M potassium chromate and 4M sodium chloride.  Also, the aqueous species viewer has been disabled and the solid species viewer has been enabled, this allows you to determine the mass and identity of any precipitates formed, but prevents you from directly reading the concentrations.


There are 6 unknowns and each student is to identify the concentration of one of them.  You are assigned your unknown based on your lab seat.  Use the following table to identify which unknown you are to report.


Unknown #:                  Seats                            Unknown #:                  Seats

A                                 1,7,13,19                     B                                  2,8,14,20

C                                 3,9,15,21                     D                                 4,10,16,22

E                                  5,11,17,21                   F                                  6,12,18,24



*As in all previous virtual lab assignments, you can access this lab through the "load homework" option of the file menu on your disk. 

Please contact your instructor if you have lost your disk or have technical problems.


Seat#_____                     Unknown:___________     Concentration: _______________M