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I sent out an e-mail about this previously but a couple of people<br>
have asked me about it concerning the upcoming midterm.<br>
<br>
Section 17.7 and questions pertaining to the flow chart and<br>
qualitative analysis was only very briefly covered in class and<br>
won't be directly covered on the quiz and exam. <big><font
size="2"><big>However, you<br>
should read this section and there were a couple of questions
included<br>
in </big></font></big>homework. <font size="2">T</font><big><font
size="2"><big>here's a sample integrative exercise at the end<br>
of this section you should be able to do w/o reading the
material<br>
in this section.</big></font></big><br>
<br>
I told people to look at Section 17.7 because it gives you some<br>
some idea and a physical application of the precipitation (Ksp)<br>
stuff you were learning in sections 17.4-17.6. <br>
<big><font size="2"><big><br>
</big></font></big>For instance, Figure 17.23 (flow chart) you
can see<br>
Ag+, Pb^2+, and Hg2^2+ precipitate easily with the addition of<br>
HCl (they form the associated chlorides). This makes sense<br>
since we saw the corresponding chlorides have small Ksp values,<br>
meaning they aren't very soluble. By the way, you learned this in<br>
1210 when you went over the solubility rules.<br>
<br>
If you look all the way at the bottom of the flowchart you will see<br>
group 2A cations. They don't form insoluble compounds with<br>
chloride so they don't react. However, they do form phosphates<br>
which are insoluble (actually most phosphates are insoluble except<br>
those of group 1A cations and NH4^+).<br>
<br>
The flowchart is effectively using selective precipitation to
separate<br>
the cations so it might help for you to read through it even though
there<br>
won't be specific questions over the qualitative analysis or
flowchart.<br>
<br>
You may also find it useful to review section 4.2, particularly the
info<br>
in Table 4.1. This is the general solubility guidelines you learned
before<br>
you knew about Ksp.<br>
<br>
<br>
Dr. Zellmer<font size="2"><br>
</font>
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