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<div class="moz-text-html" lang="x-unicode"> <big><font
size="2"><big>I mentioned this in class last week. The
textbook states NH3<br>
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 NH3 was<br>
a base. Instead people came up with the nonexistent
substance<br>
ammonium hydroxide, NH4OH, which has an OH- in the
formula.<br>
This really doesn't exist. If you put NH3 in H2O you
get NH4+ 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<br>
compound of ammonium hydroxide. Instead what happens as
the<br>
water vaporizes is the NH3 slowly comes out of soln as a
gas (which<br>
it is to begin with) and you will eventually be left
with nothing but air.<br>
<br>
A looser definition, what 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 no books I've seen state this is so and
Arrhenius<br>
did not do so).<br>
<br>
By the way, you will often see on a bottle of aqueous
NH3 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
NH3.<br>
<br>
Here's a link which also describe this,<br>
<br>
<a class="moz-txt-link-freetext"
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>
</big></font></big><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>
<big><font size="2"><big><br>
This technically applies to other substances as well.
According to his<br>
original theory the base had to have an OH (technically,
OH-) in<br>
the formula. This means the answer in the solutions
manual on<br>
Carmen to 16.14(b) (13th, 12th & 10th ed.)
technically not correct.<br>
<br>
Dr. Zellmer</big></font></big> </div>
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