<html>
<head>
<meta content="text/html; charset=UTF-8" http-equiv="Content-Type">
</head>
<body bgcolor="#FFFFFF" text="#000000">
<div class="moz-cite-prefix">On 02/13/14 06:29, wrote:<br>
</div>
<blockquote
cite="mid:C40B2F181831EF44A88CD735258278030930D7E4CA@MERCERMAIL.MercerU.local"
type="cite">
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<style type="text/css" style="display:none"><!--P{margin-top:0;margin-bottom:0;} .ms-cui-menu {background-color:#ffffff;border:1px rgb(171, 171, 171) solid;font-family:'Segoe UI WPC', 'Segoe UI', Tahoma, 'Microsoft Sans Serif', Verdana, sans-serif;font-size:11pt;color:rgb(51, 51, 51);} .ms-cui-menusection-title {display:none;} .ms-cui-ctl {vertical-align:text-top;text-decoration:none;color:rgb(51, 51, 51);} .ms-cui-ctl-on {background-color:rgb(223, 237, 250);opacity: 0.8;} .ms-cui-img-cont-float {display:inline-block;margin-top:2px} .ms-cui-smenu-inner {padding-top:0px;} .ms-owa-paste-option-icon {margin: 2px 4px 0px 4px;vertical-align:sub;padding-bottom: 2px;display:inline-block;} .ms-rtePasteFlyout-option:hover {background-color:rgb(223, 237, 250) !important;opacity:1 !important;} .ms-rtePasteFlyout-option {padding:8px 4px 8px 4px;outline:none;} .ms-cui-menusection {float:left; width:85px;height:24px;overflow:hidden}
<!--
p
{margin-top:0;
margin-bottom:0}
.ms-cui-menu
{background-color:#ffffff;
border:1px rgb(171,171,171) solid;
font-family:'Segoe UI WPC','Segoe UI',Tahoma,'Microsoft Sans Serif',Verdana,sans-serif;
font-size:10pt;
color:rgb(51,51,51)}
.ms-cui-ctl
{vertical-align:text-top;
text-decoration:none;
color:rgb(51,51,51)}
.ms-cui-ctl-on
{background-color:rgb(223,237,250)}
.ms-cui-img-cont-float
{display:inline-block;
margin-top:2px}
.ms-cui-smenu-inner
{padding-top:0px}
.ms-owa-paste-option-icon
{margin:2px 4px 0px 4px;
vertical-align:sub;
padding-bottom:2px;
display:inline-block}
.ms-rtePasteFlyout-option
{padding:8px 4px 8px 4px;
outline:none}
.ms-cui-menusection
{float:left;
width:85px;
height:24px;
overflow:hidden}
-->
--></style>
<div
style="font-size:12pt;color:#000000;background-color:#FFFFFF;font-family:Calibri,Arial,Helvetica,sans-serif;">
<p>Dr. Pounds,<br>
</p>
<p><br>
</p>
</div>
</blockquote>
<br>
First -- the cooling curve should have TWO LINES on it; one is for
where the temperature drops rapidly and the other one for where it
levels off. The intersection of these two lines is the freezing
point. If you are still confuses, please look back at the figure at
the end of the lab procedures (which has one cooling curve on it)
and then also at my sample plot on the class web page (which has all
six cooling curves on it). I am not requiring you to put all of the
cooling curves on the same plot.<br>
<br>
<blockquote
cite="mid:C40B2F181831EF44A88CD735258278030930D7E4CA@MERCERMAIL.MercerU.local"
type="cite">
<div
style="font-size:12pt;color:#000000;background-color:#FFFFFF;font-family:Calibri,Arial,Helvetica,sans-serif;">
<p>
</p>
<p>I'm confused as to how I can find the moles of solute since
it's an unknown. I'm also having difficulties with my
graphing. I can graph all of the values but I can't seem to
graph two lines on the same graph in order to figure out where
the two intersect. Thank you for your help.<br>
</p>
<p><br>
</p>
</div>
</blockquote>
Lets call the freezing point of the pure solid <img
style="vertical-align: middle"
src="cid:part1.06060600.05070405@mercer.edu" alt="$T_1$"> and the
freezing point of the solid with an unknown <img
style="vertical-align: middle"
src="cid:part2.03070300.07000500@mercer.edu" alt="$T_2$">. <img
style="vertical-align: middle"
src="cid:part3.05010203.06000403@mercer.edu" alt="$\Delta T = T_1
- T_2$">.<br>
<br>
Also, <img style="vertical-align: middle"
src="cid:part4.01010608.01030007@mercer.edu" alt="$\Delta T = K_f
m$"> where <img style="vertical-align: middle"
src="cid:part5.05020508.05070502@mercer.edu" alt="$m$"> is the
molality. The molality is moles of solute (unknown) over kg of
solution.<br>
<br>
Let's rearrange...<br>
<br>
<img style="vertical-align: middle"
src="cid:part4.01010608.01030007@mercer.edu" alt="$\Delta T = K_f
m$"><br>
<br>
<img style="vertical-align: middle"
src="cid:part7.06090108.05070500@mercer.edu" alt="$\Delta T = K_f
\frac{n}{{\mathrm{kg\ solvent}}}$"><br>
<br>
<img style="vertical-align: middle"
src="cid:part8.08030404.07080608@mercer.edu" alt="$\frac{{(\Delta
T)}{(\mathrm{kg\ solvent}})}{K_f} = n$"><br>
<br>
Since I now have <img style="vertical-align: middle"
src="cid:part9.04050001.05090300@mercer.edu" alt="$n$">, the moles
of unknown, and the mass of the unknown, I can determine its molar
mass.<br>
<br>
<br>
Does that help?<br>
<br>
<br>
<blockquote
cite="mid:C40B2F181831EF44A88CD735258278030930D7E4CA@MERCERMAIL.MercerU.local"
type="cite">
<div
style="font-size:12pt;color:#000000;background-color:#FFFFFF;font-family:Calibri,Arial,Helvetica,sans-serif;">
<p>
</p>
<p>Sincerely,<br>
</p>
<br>
<div style="color: #282828;">
<div>
<br>
<pre class="moz-signature" cols="72">--
Andrew J. Pounds, Ph.D. (<a moz-do-not-send="true" 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 moz-do-not-send="true" class="moz-txt-link-freetext" href="http://faculty.mercer.edu/pounds_aj">http://faculty.mercer.edu/pounds_aj</a>
</pre>
</div>
</div>
</div>
</blockquote>
<br>
<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>