Exp 14 help (including Ps values from eqn 6 and s.f. for logs)

[robert zellmer]

We are doing exp 14 next week.

I have help files for exp 14 for both pre-lab and post-lab for the graphs
and report.  Please take a look at the following links,

*Laboratory* 
<http://chemistry.osu.edu/%7Erzellmer/chem1250/lab/lab_1250.htm>

*Exp 14 - Help for Exp 14* 
<http://chemistry.osu.edu/%7Erzellmer/chem1250/faq/exp14.txt>


For the first link pay close attention to the volumes you should be 
using depending
on what compound you have.  You won't know which known compound until
lab.  There are 5 volumes for each compound.  These are approx.  You are 
supposed
to get close to one of these and then hold it there for awhile (about 30 
seconds by
adjusting the flame) and then read the temperature.

At the help link I've been quite specific about s.f. (especially for 
logarithms),
what should be in your discussion section, sample calculations, etc.

For the calculations you need to calculate the pressure of your sample 
in the
syringe.  You will use eqn 6 on page on page 97.  Often people will get 
negative
Ps values.  They can NOT be negative.  I've discussed this at the help 
link.  It's
because you used Celsius and not kelvin.  Remember,

KELVIN, KELVIN, KELVIN


There is no pre-lab quiz on Carmen.

*HOWEVER, there is an on-line data input prelab at the following link,*

*http://undergrad-ed.chemistry.ohio-state.edu/genchem/REPORT/*

This is a DIFFERENT site than for exp 5.  You need read the discussion and
data analysis section carefully.  Watch the exp 14 video (there's a link 
on my
web pages) and then write the procedure.  Read my help files (see the
"Laboratory" link on my class web page).  Then do the pre-lab.

For the pre-lab the data given is supposed to be similar to what you 
will obtain
in the lab for your unknown.  You are given just 3 temp, vol data 
(instead of the
five you will get in lab).   You use eqn 6 for this to calculate the 
Ps.  For the
fourth point that is the boiling pt.  You don't use eqn 6 for this. The 
vapor pressure
of the sample equals the barometric pressure given in the data (boiling 
occurs
when the VP of the liquid equals the prevailing atmospheric, barometric, 
pressure).

You will need to graph the points for the pre-lab and determine the 
slope of the
resulting best-fit line (linear fit must be used).  The easiest thing to 
do would be
use Excel for this while doing the pre-lab.

The sig. fig. for ln(P) are tricky.  It's explained in my help file
for exp 14 (see above link) and another help file I have specifically
about logs and s.f.   I've sent both links out before but here they are
again.  Sig. fig. for logarithms is also explained in Appendix A
of the textbook.

*Manipulating Logs and Sig. Figs.* 
<http://chemistry.osu.edu/%7Erzellmer/chem1250/faq/sig_fig_logs.txt>


Dr. Zellmer
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