<html xmlns:v="urn:schemas-microsoft-com:vml" xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:w="urn:schemas-microsoft-com:office:word" xmlns:m="http://schemas.microsoft.com/office/2004/12/omml" xmlns="http://www.w3.org/TR/REC-html40">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=us-ascii">
<meta name="Generator" content="Microsoft Word 15 (filtered medium)">
<style><!--
/* Font Definitions */
@font-face
{font-family:"Cambria Math";
panose-1:2 4 5 3 5 4 6 3 2 4;}
@font-face
{font-family:Calibri;
panose-1:2 15 5 2 2 2 4 3 2 4;}
/* Style Definitions */
p.MsoNormal, li.MsoNormal, div.MsoNormal
{margin:0in;
font-size:11.0pt;
font-family:"Calibri",sans-serif;}
a:link, span.MsoHyperlink
{mso-style-priority:99;
color:#0563C1;
text-decoration:underline;}
span.EmailStyle17
{mso-style-type:personal-compose;
font-family:"Arial",sans-serif;
color:windowtext;}
.MsoChpDefault
{mso-style-type:export-only;
font-family:"Calibri",sans-serif;}
.MsoPapDefault
{mso-style-type:export-only;
mso-margin-top-alt:auto;
mso-margin-bottom-alt:auto;}
@page WordSection1
{size:8.5in 11.0in;
margin:1.0in 1.0in 1.0in 1.0in;}
div.WordSection1
{page:WordSection1;}
--></style><!--[if gte mso 9]><xml>
<o:shapedefaults v:ext="edit" spidmax="1026" />
</xml><![endif]--><!--[if gte mso 9]><xml>
<o:shapelayout v:ext="edit">
<o:idmap v:ext="edit" data="1" />
</o:shapelayout></xml><![endif]-->
</head>
<body lang="EN-US" link="#0563C1" vlink="#954F72" style="word-wrap:break-word">
<div class="WordSection1">
<p class="MsoNormal"><span style="font-family:"Arial",sans-serif">I mentioned this in class last Thursday. The textbook states
<br>
NH<sub>3</sub> is an Arrhenius base. Someone had a question about this.<br>
<br>
The book is technically incorrect. The original definition stated<br>
that OH- was part of the compound and that compound when put<br>
in water released the OH-, making the solution basic (inc. the conc.<br>
of OH-). This theory wasn't able to correctly explain why NH<sub>3</sub> was<br>
a base. Instead people came up with the nonexistent substance<br>
ammonium hydroxide, NH<sub>4</sub>OH, which has an OH- in the formula.<br>
This really doesn't exist. If you put NH<sub>3</sub> in H<sub>2</sub>O you get NH<sub>4</sub><sup>+</sup> ions<br>
and OH- ions, which we can see using Bronsted-Lowry Theory.<br>
However, if you allow the water to evaporate you don't get a compound<br>
of ammonium hydroxide. Instead what happens as the water<br>
vaporizes is the NH3 slowly comes out of soln as a gas (which it is<br>
to begin with) and you will eventually be left with nothing but air.<br>
<br>
A looser definition, which the book uses, is an Arrhenius base is<br>
any substance that increases the conc. of OH- in an aqueous soln.<br>
NH3 does inc. the conc. of OH-. But again, this does not strictly<br>
fit the definition of an Arrhenius base. Using this criteria any<br>
anion that acts as a base would be considered an Arrhenius base<br>
(such as F- and books don’t state this is so).<br>
<br>
By the way, you will often see on a bottle of aqueous NH<sub>3</sub> the name<br>
ammonium hydroxide. This is a misnomer (as I explained above) but<br>
has kind of stuck for the name of an aqueous solution of NH<sub>3</sub> .<br>
<br>
Here's a link which also describe this,<br>
<br>
<a href="http://www.chemteam.info/AcidBase/Arrhenius-AcidBase.html">http://www.chemteam.info/AcidBase/Arrhenius-AcidBase.html</a><br>
<br>
Below are some more interesting links dealing with this and<br>
Arrhenius (quite a prolific scientist). I don't necessarily like using<br>
Wikipedia as a direct reference but you can find other links there<br>
to check on things.<br>
<br>
<a href="https://h2g2.com/edited_entry/A708257">https://h2g2.com/edited_entry/A708257</a><br>
<br>
<a href="https://h2g2.com/edited_entry/A692796">https://h2g2.com/edited_entry/A692796</a><br>
<br>
<a href="https://en.wikipedia.org/wiki/Svante_Arrhenius">https://en.wikipedia.org/wiki/Svante_Arrhenius</a><br>
<br>
<a href="https://en.wikipedia.org/wiki/Base_%28chemistry%29">https://en.wikipedia.org/wiki/Base_(chemistry)</a><br>
<br>
This technically applies to other substances as well. According to his<br>
original theory the base had to have an OH (technically, hydroxide ion,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Arial",sans-serif">OH-) in the formula. This means the answer in the solutions manual on<br>
Carmen to 16.14(b) (13th, 12th & 10th ed.) is technically not correct.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Arial",sans-serif"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Arial",sans-serif">Finally, one last thing. If there’s a midterm question about whether<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Arial",sans-serif">NH3 is an Arrhenius base you should say it is since the textbook states<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Arial",sans-serif">this.<br>
<br>
Dr. Zellmer <o:p></o:p></span></p>
</div>
</body>
</html>