exp 16 video in pre-lab

[Zellmer, Robert]

There are some changes to the procedure shown in the video.



1)  Thermometer is incorrect. You're using a lollipop thermometer.



2)  You don't weigh out the sample as shown by weighing

    the vial before and after adding sample to the test tube.



    Instead you use a weigh boat.  You tare the balance.

    Put an empty weigh boat on the balance (they weigh

    around 3 g).  Make a mental note of the mass.  Add

    about 0.1 g of sample.  Record this mass (boat + sample).

    Add the sample to the test tube.  Go back and reweigh

    the "empty" weigh boat (after taring the balance).  Some

    sample will likely have remained behind in the weigh boat.

    You get the mass of sample actually added to the test tube

    by difference.



    While adding the sample it's easiest to put the test tube

    in the air jacket.  Remove the thermometer apparatus

    slightly, just enough to pour in your solute.  Try not to get

    the solute on the sides of the tube.  It must all be dissolved

    in the solvent before proceeding.  Do NOT put the thermometer

    apparatus on the desk or in another beaker.  Doing so could cause

    two problems: (1) you pick up something from the desk top or from

    inside the beaker and (2) you lose some of your solvent or solution

    as the apparatus rests on whatever you put it on.



Dr. Zellmer
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