<html>
<head>
<meta content="text/html; charset=windows-1252"
http-equiv="Content-Type">
</head>
<body bgcolor="#FFFFFF" text="#000000">
<div class="moz-cite-prefix">On 03/29/2015 12:25 PM, wrote:<br>
</div>
<blockquote
cite="mid:C40B2F181831EF44A88CD73525827803130F1778B4@MERCERMAIL.MercerU.local"
type="cite">
<meta http-equiv="Content-Type" content="text/html;
charset=windows-1252">
<style type="text/css" style="display:none"><!-- p {margin-top:0;margin-bottom:0;} --></style>
<div class="" role="textbox" useinlinestyle="true" dir="ltr"
style="outline: none; font-size: 12pt; color: rgb(0, 0, 0);
font-family: Calibri, Arial, Helvetica, sans-serif, 'Apple Color
Emoji', 'Segoe UI Emoji', NotoColorEmoji, 'Segoe UI Symbol',
'Android Emoji', EmojiSymbols; background-color: rgb(255, 255,
255);">
<p>Hi Dr. Pounds,</p>
<p>This is from CHM 112. I have a question about the buffers lab
that's due Tuesday. I wondering how you wanted us to calculate
the pKa of the buffer and the Ka of the acid. I was thinking I
would need to use the concentration of the acid, but I see
that we were only given the grams of the unknown acid, without
its molar mass. Please help. Thanks!</p>
</div>
</blockquote>
<font face="serif"><br>
So at the midpoint of titration (halfway to the endpoint) the pH
is equal to the pKa. In the experiment you split your uknown in
two and titrated it to the endpoint. You then recombined the two
solutions. By definition the recombined solution was at the
halfway to then endpoint. You measured the pH then -- and that
should also be the pKa.<br>
<br>
</font><br>
<pre class="moz-signature" cols="72">--
Andrew J. Pounds, Ph.D. (<a class="moz-txt-link-abbreviated" href="mailto:pounds_aj@mercer.edu">pounds_aj@mercer.edu</a>)
Professor of Chemistry and Computer Science
Mercer University, Macon, GA 31207 (478) 301-5627
<a class="moz-txt-link-freetext" href="http://faculty.mercer.edu/pounds_aj">http://faculty.mercer.edu/pounds_aj</a>
</pre>
</body>
</html>