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Unformatted text preview: be separated by their insoluble salts. Group IV
includes Ba +2 and Ca+2 (and many qualitative analysis schemes include Sr+2 in this group
as well). They are precipitated out as carbonates.
Separation of Group IV from group V:
Verify that the decantate from the separation step of group III is still alkaline; if it
is not, add concentrated ammonium hydroxide until it is. Once alkaline, add 1 mL of
ammonium carbonate; barium and calcium will precipitate out as carbonates. Centrifuge
and decant. Once separated, dissolve the solid in hot dilute acetic acid. Split the solution
into two parts.
Verification for Ba +2 :
To one portion from the above step, add a few drops of potassium chromate. A
precipitate, barium chromate, confirms the presence of barium.
Verification of Calcium:
To the other solution, add a few drops of sodium oxalate. The presence of a
precipitate verifies calcium.
Group V ions can be thought of as “everything left over.” We will assume this
“group” contains only K+, although many qualitative analysis schemes include Na+, Mg+2
and NH4 + as well.
Flame test for K+ :
Take an iron loop and “clean” it by putting it into a hot flame until the loop glows
red hot (be careful not to burn yourself). Allow the loop to cool, and dip it in the
remaining decantate from the group IV separation step. Be sure a drop is on the wire.
Put the drop into the flame; a red flame verifies potassium.
Calculations: Dakota State University page 199 of 232 Experiment 19: Qualitative Analysis General Chemistry I and II Lab Manual None. Dakota State University page 200 of 232 Experiment 19: Qualitative Analysis General Chemistry I and II Lab Manual Observations:
Design your own observation page. Dakota State University page 201 of 232 Experiment 19: Qualitative Analysis General Chemistry I and II Lab Manual Pre-Lab Questions:
Make an outline of each procedure before you perform the steps. Dakota State University page 202 of 232 Experiment 19: Qualitative Analysis General Chemistry I and II Lab Manual Post-Lab Questions:
Discuss your results, which you trust, which you do not and why. Discuss possible
sources of error. Dakota State University page 203 of 232 Experiment 20: Beer’s Law General Chemistry I and II Lab Manual Experiment 20: Beer’s Law
Purpose: To gain an understanding of basic spectroscopy
Pfffft: Cartoon sound made whe n a character passes wind Background:
See “Using the Pasco System” and “using HyperChem”
It is far too easy to fall into the trap of expecting information to be given in a
classroom setting. When working to resolve a problem, scientists often do not have
anybody to simply give them the answer, and are usually lucky if they can find some
body of work that is at least close enough to the type of problem they have to give them
an idea of where to begin with their work. A big part of what we are trying to accomplish
in this course is to get our students to stop expecting answers to be given, and start
thinking about how to approach problems to solve them by themselves without the help
of an “expert.” This is not an easy thing to do, since it does involve a new way of
thinking, but we are c...
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