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We did a new exp 17 last week. Here's a few things which might
help.<br>
<br>
1) My on-line example<b> </b>is for the old exp. You can still
look at it to<br>
see what a zero-order plot should look like. If you scroll down<br>
to the bottom you'll find what you might find for the first and
second<br>
order plots might look like. See item #6 below for more
explanation<br>
and links.<br>
<br>
2) Your initial concs. for each solution are different. You need to
do a<br>
dilution calc (M2*V2=M1*V1) to get the initial Dye conc.,
[Dye]o,<br>
for each solution at the moment of mixing. The M1 is the conc.
on<br>
the bottle. The V1 are the volumes you were told to use in lab,
they<br>
may be different than what was in the manual since we made some<br>
changes as we went through the week and you didn't have to have<br>
volumes which exactly matched those in the manual for the Dye
and<br>
the water. Use your recorded volumes from lab. The V2 should
be<br>
the total volume of Dye, H2O and bleach at the moment of mixing.<br>
This should be close to 40 mL.<br>
<br>
3) The new manual gives an idea of what the report sheet should look
like<br>
and what the tables should look like. Use Excel to make your
data<br>
tables and the report sheet. The tables in the manual pages
won't<br>
work well in that you can't program equations into them. Make
sure<br>
you have the proper headings, units, s.f., etc. Import your
tables from<br>
Excel into the report. Do NOT scan tables or graphs and include
a scan.<br>
<br>
My suggestion is to use a different worksheet in Excel for the
data for<br>
each solution for Part A data. That means you'll have 4
worksheets in<br>
Excel, one for each solution and each table would be on a single
page<br>
in the report. I'm referring to the table at the bottom of page
2 of the<br>
report sheet in the manual pages on Carmen for Part A time,
absorbance<br>
and conc. data.<br>
<br>
Make a worksheet for solution 1 (i.e. get everything set up
correctly in<br>
this table, labels, units, s.f., equations) and then copy the
worksheet for<br>
soln 1 to three other worksheets for solutions 2, 3 and 4. Then
all you<br>
have to do is change your times and absorbance values in the
tables for<br>
solutions 2, 3 and 4. If you do this before making your graphs
the s.f.<br>
set in your tables should transfer over to the graphs. The
graphs also need<br>
to have the correct s.f. and units. <br>
<br>
Since you'll have multiple s.f. for the Abs values (ranging from
1 to 3,<br>
mostly 2) just use 2 s.f. for the y-axis (conc. related data)
you derive from<br>
the Abs using the Beer's law eqn. Go ahead and use 3 s.f. for
the slopes<br>
and rate constants.<br>
<br>
If you have any negative Abs readings you can't use that data.
<br>
<br>
4) Sample calculations:<br>
<br>
[Dye]o and [Bleach]o (at the moment of mixing)<br>
Beer’s law constant (slope calc.)<br>
[Dye]t<br>
ln [Dye]t<br>
1 / [Dye]t<br>
Rate constant from any slope (graph 3 or 4)<br>
Average of the rate constants<br>
Average deviation for rate constants<br>
<br>
5) You are suppose to report the Average value of the rate constants
and<br>
the average deviation of the rate constants. See the link at
the "Laboratory"<br>
link which discusses the treatment of numerical data (Appendix F
in your<br>
manual),<br>
<br>
<a
href="https://www.asc.ohio-state.edu/zellmer.1/chem1250/lab/App_F_1250_lab_manual.pdf"><b>Treatment
of Numerical Data (Error Analysis, sig. fig., graphing)</b></a><br>
<br>
6) Graphs<br>
<br>
A) Beer's law graph<br>
<br>
This graph should have <font color="#ff0000">6 </font>data
points (5 solutions and the origin (0,0))<br>
and be forced through the origin (an option when you do the
trend<br>
line). You will know if you didn't do this if your eqn. has an
intercept.<br>
The slope of this graph should be over 20,000.<br>
<br>
B) Zero-order graph<br>
<br>
I have an example of a good zero-order graph for the old exp 17.<br>
Your graph won't look exactly the same but should be similar.<br>
<br>
<a
href="https://www.asc.ohio-state.edu/zellmer.1/chem1250/lab/exp17/exp17_web_graph2_ex.pdf"
moz-do-not-send="true">Zero-Order graph</a> - Examples of a good
graph<br>
<br>
These examples are for the zero-order plot. This is actual data<br>
and graphs from a previous year that I cleaned up. You can use<br>
an exponential or parabola for the zero-order plot (which ever<br>
seems to give a better fit, usually exponential). Do <b>NOT </b>use
a<br>
<b>linear </b>fit for the zero-order plot.<br>
<br>
Note two lines cross toward the end. They shouldn't cross. There<br>
was something wrong with the data toward the end of the run<br>
for one of the solutions. A zero order graph should eventually<br>
approach zero so the lines for all 4 solutions will likely
converge<br>
toward the end of the lines. If they cross well before near the
end<br>
that's a problem. When this happens you will notice in graphs<br>
3 or 4 for the 1st and 2nd order graphs (which ever produces the<br>
most parallel lines) the slope for the line which crosses the
others isn't<br>
as similar to the slopes for the other lines (not as closely
parallel).<br>
In this case you should report all four rate constants on the
report<br>
sheet but might consider not including the "bad" rate constant
in<br>
your average. It depends on how different it is from the other
three<br>
You should discuss this in the Discussion section of the report.<br>
<br>
C) 1st and 2nd order graphs<br>
<br>
For the first and second-order graphs (graphs 3 and 4) you
should use<br>
<b>LINEAR</b> fits (trend lines) for both graphs. Do NOT go
back and fit either<br>
to something other than linear. You are looking to see which
graph has lines<br>
that are more closely parallel. Generally speaking, if you have
good data<br>
you will see a distinct difference between the two graphs.
Also, which ever<br>
graph has lines which are more closely parallel will often
produce a better<br>
straight line fit to the points.<br>
<br>
See the following link for examples using data from the old exp
17 of what<br>
you might see,<br>
<br>
<a
href="https://www.asc.ohio-state.edu/zellmer.1/chem1250/lab/exp17/exp17_web_graphs_3_4_exs.pdf"
moz-do-not-send="true">Graphs 3 & 4</a> - Exs of what Graphs 3
& 4 might look like<br>
<br>
What you should see is one of these two graphs will give
parallel lines and<br>
the other won't. So if the first-order graph has parallel
straight lines the 2nd<br>
order graph will have lines which clearly aren't parallel and
the data clearly<br>
doesn't fit a linear trend line. If the 2nd-order graph has
parallel straight lines <br>
the 1st-order graph will have lines which clearly aren't
parallel and the data<br>
clearly doesn't fit a linear trend line. <br>
<br>
D) Misc.<br>
<br>
For graph 3 (1st-order) the label for the x-axis will likely be
at the <br>
top of the graph. You can move it to the bottom. You actually <br>
have to right-click on the Y-axis, choose "Format Axis" and then
<br>
choose "Value (X) axis crosses at:" or "Horizontal axis
crosses:" <br>
and set this to the minimum value on the Y-axis. It should move
<br>
to the bottom of the graph. <br>
<br>
Set all the graphs to be printed in <b>LANDSCAPE </b>mode
(normally the<br>
default for Excel). This gives better looking graphs. Set
margins to<br>
zero.<br>
<br>
7) What if one of your solutions gives "bad" data? How will you
know?<br>
Lets say for your zero-order graph one of the lines crosses the
other<br>
lines well before 4 minutes. What should you do? Do your
zero-order<br>
graph twice, once with all four solutions and once with only the
three<br>
good ones. Then do the first and second-order graphs with only
the<br>
three good ones.<br>
<br>
8) Don't forget to discuss how you chose the order based on graphs 3
and 4.<br>
Also, discuss <b>WHY </b>one of the graphs should have lines
which are parallel.<br>
Compare the rates for the four solutions and do they make sense.
Don't<br>
forget your rate constants and the rate law. Look at the "<b>Points
to Consider</b>".<br>
<br>
Please <b>remember</b>, <b>my Excel example </b>is just that,
an <b>example </b>of what<br>
to do and how to do it. <b>It is not a complete example and
it's for the older<br>
exp 17.<br>
</b> <br>
I hope this helps.<br>
<br>
<br>
Dr. Zellmer <br>
<br>
<b></b>
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