exp 16 question - mass added and total mass

[robert zellmer]

I've often receive essentially the same questions regarding exp 16 and 
it's pre-lab.
They deal with the mass of sample added and the total mass of sample. This
will also apply during the exp, the report and the post-lab. Also, I get 
questions
about sig. fig.  I'll send that in a follow-up e-mail.

If you look at the procedure you'll see you first determine the f.p. of 
the pure
cyclohexane (solvent).  Then you start adding solute, which lowers the 
f.p.  How
much the f.p. drops depends on the amount of solute present.  For each 
of the
trials in part B you will add some solute.  First you add about 0.3 g in 
trial 1 and
take the f.p. of this solution.  Then you ADD ~ 0.2 g more of solute.  
Thus, the
TOTAL mass of solute will be ~ 0.5 g.  Then in trial 3 you add another 
~0.1 g of
solute.  You will then have a total of ~0.6 g of solute in trial three.  
In each of the
trials you need to calculate the molality of the solute in the 
solution.  To do this you
need the TOTAL mass in each trial in order to calculate the TOTAL moles 
of solute
in each trial.

Dr. Zellmer