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

[Zellmer, Robert]

You are doing exp 14 this week.  We completed the material associated with this
experiment last week.  You can find all the info you need for the questions in the
pre-lab and the calculations in the manual.

I have help files for exp 14 for both pre-lab and post-lab for the graphs and report.
Don't attempt the pre-lab until you've read the manual, the e-mails I'm sending and
the information at the following links,

Laboratory<https://www.asc.ohio-state.edu/zellmer.1/chem1250/lab/lab_1250.htm>

Exp 14 - Help for Exp 14<https://www.asc.ohio-state.edu/zellmer.1/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 30-60 seconds by
adjusting the flame) and then read the volume and temperature. You don't have to
be exactly on the temp.  If you try it will take all day to get the exp done.

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.   LOOK at
this LINK.

For the calculations you need to calculate the pressure of your sample in the
syringe.  You will use eqn 6 on page 95 for the Ps values from the V & T data.
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 an on-line data input prelab at the following link,

https://uglabs.cbc.osu.edu/1250/pre-postlabs.php

This is the SAME site as for the other pre-labs and post-labs.  You can get to it via
the module for exp 14 on Carmen (it takes you to the same site).  You need read the
discussion and data analysis section carefully.  Watch the exp 14 video (there's a
link on my web pages for videos).  You can watch the video in the pre-lab and then
get out.  As long as you don't submit you can restart it.  Read my help files (see the
"Laboratory" link on my class web page).  Then write the procedure and do the pre-lab.

Read the instructions on the landing page before clicking on the "Prelab" link.
Once you get to the prelab click on the Policies and Procedures link at the
very bottom,

    https://uglabs.cbc.osu.edu/1250/pre-postlabs.php

Also, click on the "Instructions" box near the upper-left hand corner of the
page.  This will give some general instructions and ones more specific to this
exp.

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 5 temp/vol data points, just like you'll
get in the exp.   You use eqn 6 for this date to calculate the Ps.  There are two
boiling points, one determined at the barometric pressure for the day (as given
in the data) and the other is the normal b.p.  You do NOT use eqn 6 for these.
Boiling occurs when the vapor pressure (VP) of the liquid equals the prevailing
atmospheric (barometric) pressure.  The normal b.p. is when the VP equals the
prevailing barometric pressure when it is 1 atm.  Both of these are given for the
pre-lab.  For the exp, the b.p. is obtained the day of lab at the barometric pressure
for that day.  You'll get this in the provided data tables with the other data for the
lab.  You'll need to look up the normal b.p. in the CRC (see my web page).

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
to use Excel for this while doing the pre-lab.  You will have two b.p. data points
on the graph, the literature value and exp value, as explained above.  Your graphs
for the report will have 7 data points.  You'll see the same for 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.<https://www.asc.ohio-state.edu/zellmer.1/chem1250/faq/sig_fig_logs.txt>


Dr. Zellmer
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