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<div class="moz-text-html" lang="x-unicode"> <big><font size="2"><big>The
following is based on reports I've seen in the past for
exp 14.<br>
There are always some good reports but many people have
problems.<br>
<br>
</big></font></big><big><font size="2"><big>There seemed to
be some problems with sig. fig. in the table (especially<br>
for Ps or ln(Ps)) and s.f. on the axes of the graphs. See
my on-line discussion<br>
of s.f. for Ps and for logarithms (and appendix A of the
textbook). This was<br>
sent out before the pre-lab but people still made
mistakes.<br>
</big></font></big><br>
<big><font size="2"><big><a
href="https://www.asc.ohio-state.edu/zellmer.1/chem1250/faq/exp14.txt"><b>Exp
14 - Help for Exp 14</b></a><br>
<br>
</big></font></big><big><font size="2"><big><a
href="https://www.asc.ohio-state.edu/zellmer.1/chem1220/faq/sig_fig_logs.txt"><b>Manipulating
Logs and Sig. Figs.</b></a><br>
<br>
</big></font></big><br>
<big><font size="2"><big>Also, many people didn't include what
should have been included in the<br>
Results/Discussion and Conclusion sections. I point out in
class some of<br>
what you should be discussing for exp 14 in terms of the
delta(Hv) values for<br>
the compounds and attractive forces. I go over this while
discussing the<br>
Clausius-Clapeyron Eqn and the graph in the notes. I also
explain in some<br>
detail what you should be doing with the graphs,
significant figures (especially<br>
for Ps and ln(Ps)) and what should be in the
Results/Discussion and Conclusion<br>
sections for this exp. <br>
<br>
</big></font></big><big><font size="2"><big><big><font
size="2"><big>In the Discussion section you should
include the delta(Hv) values for the<br>
compounds. You should discuss if you got the
correct order for the </big></font></big><big><font
size="2"><big><big><font size="2"><big>delta(Hv)<br>
values </big></font></big>for the cmpds and
how you know based on the attractive forces present<br>
between the molecules and what those AF forces are.
If you get the wrong order<br>
you should explain what the order should be and how
you know based on the<br>
AF present. You can use the b.p. from the CRC to
back up your discussion.<br>
However, the b.p. data should not be used as your
primary line of reasoning.<br>
You can find the on-line CRC link on Carmen
("Content" tab) or my web<br>
pages,<br>
</big></font></big><br>
<big><font size="2"><big><a
href="http://hbcpnetbase.com.proxy.lib.ohio-state.edu"><b>CRC
Handbook of Chemistry and Physics</b></a><br>
</big></font></big> <br>
</big></font></big>You don't need to formally source this
data if it comes from the CRC (just mention<br>
it's from the CRC). If you use any other source you will need
to have <br>
a more extensive reference in your report. <br>
<br>
<big><font size="2"><big>For the graph, do a "scatter" graph
with points only (no connecting lines). Then<br>
do a trend </big></font></big><big><font size="2"><big>line
(linear). You don't want to play "connect the dots" with
the data.<br>
Print the equation for each line (and R^2). See my
example for exp 14 and the<br>
what the graph should look like (it should have 7 data
points).<br>
</big></font></big><br>
<big><font size="2"><big><a
href="https://www.asc.ohio-state.edu/zellmer.1/chem1250/lab/exp14.pdf"
moz-do-not-send="true"><b>Using MS EXCEL for Chem Lab -
exp. 14 example (Vapor Pressure exp. - old exp 13)</b></a>
<br>
<br>
</big></font></big><big><font size="2"><big><a
href="https://www.asc.ohio-state.edu/zellmer.1/chem1250/lab/exp14_final_graphA.pdf"
moz-do-not-send="true"><b>Exp 14 (dHv) - Example Graph
for Compounds</b></a><br>
<br>
</big></font></big><big><font size="2"><big>Many of the
graphs had problems with spacing. The graphs did not take
up<br>
the whole page or the points didn't occupy most of the
space on the page.<br>
Some didn't have the boiling points included on the graphs
or labeled. The<br>
boiling points should be included in the data set and
labeled on the graph.<br>
</big></font></big><big><font size="2"><big><big><font
size="2"><big><big><font size="2"><big>Some did have
the b.p. but did not include them in the
best-fit line and did not<br>
label them. The boiling points are your best
data points, particularly the normal<br>
b.p. from the CRC manual (that's your best
point). Don't include your exp.<br>
b.p. in the fit if it's way off from where it
should be but still include it on the<br>
graph.<br>
</big></font></big> </big></font></big><br>
Many people did not include inherent errors. I believe I
explained in lecture<br>
at some point and my web page and e-mails what this
means. These are errors<br>
due to the way the experiment is being carried out which
you have minimal to<br>
no control over. For instance, for exp 6 (coffee-cup
calorimeter) the most<br>
obvious inherent error would be, it was a simple coffee
cup. While it really<br>
didn't do a terrible job, it wasn't a "perfect"
calorimeter and heat could get in<br>
or out, especially via the lid. Another one would be the
fact the thermometer<br>
could only be read to the first decimal place. For most
parts that limited the<br>
delta T to 2 (maybe 3) s.f. That ultimately limited the
sig. figs. in the heat<br>
capacity for the calorimeter and the enthalpies for the
reactions. Not swirling<br>
the solution in the cup to equilibrate the temperature
throughout the solution<br>
would not be an inherent error. That's your mistake.
Splashing water out of<br>
the cup when you dropped in the copper cylinders is not an
inherent error<br>
(again this is your error). This doesn't mean "human"
error can not be<br>
considered inherent error. It depends on the experiment.
Matching colors<br>
for a result has a human element to it but it could be
considered an inherent<br>
error depending on how it's done and what it's used for.<br>
<br>
Make sure you look at the "<b>Points to Consider</b>"
section in the manual (at the<br>
end of the write-up for the experiment in the manual).
These give some idea of<br>
things to consider and discuss. </big></font></big><big><font
size="2"><big>It is not all inclusive and there may be other
things<br>
you need to address. You should </big></font></big><big><font
size="2"><big>ALWAYS address whether your results are<br>
correct or reasonable (since you don't always know if
they're correct) and support<br>
your analysis with data, your results and information from
the book, lab manual<br>
and lecture.<br>
<br>
This is not all inclusive of the problems I saw but some
of the main<br>
ones (many of the same errors repeated by multiple
students over<br>
multiple years).<br>
<br>
Dr. Zellmer</big></font></big> </div>
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