<![CDATA[
<body bgcolor="#ffffff" text="#000000" link="#FF0000" vlink="#000099" alink="#000099"><!--mstheme-->
<script language="JAVASCRIPT">
<!--
if (navigator.onLine){
document.write("<!-- Spidersoft WebZIP Ad Banner Insert -->");
document.write("<TABLE width=100% border=0 cellpadding=0 cellspacing=0>");
document.write("<TR>");
document.write("<TD>");
document.write("<ILAYER id=ad1 visibility=hidden height=60></ILAYER>");
document.write("<NOLAYER>");
document.write("<IFRAME SRC='http://www.spidersoft.com/ads/bwz468_60.htm' width=100% height=60 marginwidth=0 marginheight=0 hspace=0 vspace=0 frameborder=0 scrolling=no></IFRAME>");
document.write("</NOLAYER>");
document.write("</TD>");
document.write("</TR>");
document.write("</TABLE>");
document.write("<!-- End of Spidersoft WebZIP Ad Banner Insert-->");
}
//-->
</script>
<a name="top"></a>
<center>
<h1><!--mstheme--><font color="#000099">
<img src="../../media/acidbase/acidbasetitle.gif" alt="acidbasetitle.gif" width="313" height="41">
<!--mstheme--></font></h1>
</center>
<p>Typically, we recognize acids and bases by their simple properties,
such
as taste. We know that a lemon is sour, so it is acidic. Bases tend to
taste bitter. Acids and bases also change the color of certain dyes, such
as phenolphthalein and litmus. Acids change litmus treated paper from
blue to red. Acids
change basic phenolpthalein from red to colorless. Bases change litmus
treated paper from
from red to blue and phenolphthalein from colorless to pink. Acids
and bases neutralize the action of each other. This is why we take
antacids for
stomachaches, because the antacid is a base, and neutralizes the acid in
the stomach.</p>
<!--mstheme--></font><!--msthemelist--><table border="0" cellpadding="0" cellspacing="0" width="100%">
<!--msthemelist--><tr><td valign="baseline" width="42"><img src="../../../../_themes/education/blbull1.gif" width="15" height="15" hspace="13"></td><td valign="top" width="100%"><!--mstheme--><a href="#arr">Arrhenius Concept of Acids and Bases</a>
<!--msthemelist--><tr><td valign="baseline" width="42"><img src="../../../../_themes/education/blbull1.gif" width="15" height="15" hspace="13"></td><td valign="top" width="100%"><!--mstheme--><a href="#bl">Bronsted-Lowery Concept of Acids and Bases</a>
<!--msthemelist--><tr><td valign="baseline" width="42"><img src="../../../../_themes/education/blbull1.gif" width="15" height="15" hspace="13"></td><td valign="top" width="100%"><!--mstheme--><a href="#lewis">Lewis Concept of Acids and Bases</a>
<!--msthemelist--><tr><td valign="baseline" width="42"><img src="../../../../_themes/education/blbull1.gif" width="15" height="15" hspace="13"></td><td valign="top" width="100%"><!--mstheme--><a href="#equil">Equilibrium with Acids and Bases</a>
<!--msthemelist--></table><!--mstheme-->
<!--msthemeseparator--><p align="center"><img src="../../../../_themes/education/blrule.gif" width="600" height="10"></p>
<a name="arr"></a>
<center>
<h2><!--mstheme--><font color="#0033CC">Arrhenius Concept of Acids and Bases<!--mstheme--></font></h2>
</center>
<p>This guy named Arrhenius concocted the first successful concept of
acids and bases. He did this by defining acids and bases according to the
effect these substances have on water. The Arrhenius concept of acids and
bases
is as follows: an acid is a
substance that when dissolved in water increases the concentration of the
hydrogen ion, H<sup>+</sup>. A base is a substance that when dissolved
in water increases the concentration of the hydroxide ion, OH<sup>-</sup>.
<br>
<p>The hydrogen ion, is not just a bare proton, it is a proton bonded to a
water molecule, H<sub>2</sub>O. This results in a hydronium ion,
H<sub>3</sub>O<sup>+</sup>.<p>
<br>
<p>In Arrhenius's thoery, something that is a strong acid is a substance
that completely ionizes in aqueous solution to give a hydronium ion,
H<sub>3</sub>O<sup>+</sup>, and an anion. An anion is a negatively
charged
ion. An example of a strong acid is perchloric acid:</p>
<br>
<center>
HClO<sub>4</sub>(aq) + H<sub>2</sub>O(l) ->
H<sub>3</sub>O<sup>+</sup>(aq) + ClO<sub>4</sub><sup>-</sup>(aq)
</center>
<br>
<p>What is going on above is that we have perchloric acid in an aqueous
soluion. This perchloric acid ionizes entirely and results in an
hydronium
ion and a perchlorate anion. Some other examples of strong acids would be:
HI, HBr, HCl, HNO<sub>3</sub>, and H<sub>2</sub>SO<sub>4</sub>.<p>
<br>
<p>Now on to bases...A strong base is something that completely ionizes in
aqueous solution to give a hydroxide ion and a cation. A cation is a
positively charged ion. Strong bases are most of the hydroxides of Group
IA
elements and Group IIA elements including LiOH, NaOH, KOH,
Ca(OH)<sub>2</sub>,
Sr(OH)<sub>2</sub> and Ba(OH)<sub>2</sub>.</p>
<br>
<p>Many of the acids and bases that we encounter in our everyday lives
are
not strong acids, they are considered weak. Weak acids do not completely
ionize in solution, but exist in equilibrium. Let's look at the reaction
for acetic acid:</p>
<br>
<br>
<center>
<IMG src="../../media/acidbase/equation1.gif" alt="base equation" width="276" height="13" >
</center>
<br>
<!--msthemeseparator--><p align="center"><img src="../../../../_themes/education/blrule.gif" width="600" height="10"></p>
<center>
<a href="#arr">Arrhenius Concept of Acids and Bases</a> |
<a href="#bl">Bronsted-Lowery Concept of Acids and Bases</a> |
<a href="#lewis">Lewis Concept of Acids and Bases</a> |
<a href="#equil">Equilibrium with Acids and Bases</a> |
<a href="#top">Top of Page</a>
</center>
<!--msthemeseparator--><p align="center"><img src="../../../../_themes/education/blrule.gif" width="600" height="10"></p>
<a name="bl"></a>
<center>
<h2><!--mstheme--><font color="#0033CC">Bronsted-Lowery Concept of Acids and Bases<!--mstheme--></font></h2>
</center>
<br>
<p>The Bronsted-Lowery concept of acids and bases is that acid-base
reactions can be seen as proton-transfer reactions. This results in acids
and
bases being able to be defined in terms of this proton (H<sup>+</sup>)
transfer. According to the Bronsted-Lowery concept, acids donate a proton
in
a proton-transfer reactions. Bases accept the proton in a proton-transfer
equation. As an example, lets look at the reaction of hydrochloric acid
with ammonia. When we write it as an ionic equation we get:</p>
<br>
<br>
<center>
H<sub>3</sub>O<sup>+</sup>(aq) + Cl<sup>-</sup>(aq) + NH<sub>3</sub>(aq) ->
H<sub>2</sub>O(l) + NH<sub>4</sub><sup>+</sup>(aq) + Cl<sup>-</sup>(aq)
</center>
<br>
<br>
<br>
which reduces to:
<br>
<center>
H<sub>3</sub>O<sup>+</sup>(aq) + NH<sub>3</sub>(aq) ->
H<sub>2</sub>O(l) + NH<sub>4</sub><sup>+</sup>(aq)
</center>
<br>
<br>
because there is two Cl<sup>-</sup>(aq) one each side. We now have the
net ionic equation after we cancel out the "spectator
ions"(Cl<sup>-</sup>).
<br>
<br>
<p>What happens in this reaction in aqueous solution is a proton
transfer. According to the Bronsted-Lowery concept, acids donate a proton
in
a proton-transfer reactions. Bases accept the proton in a proton-transfer
equation. As an example, lets look at the reaction of hydrochloric acid
with ammonia shown above. What happens in this reaction in aquesous
solution is that a poton is transferred from H<sub>3</sub>O<sup>+</sup>
to
NH<sub>3</sub>. This results in H<sub>3</sub>O<sup>+</sup> losing a
(H<sup>+</sup>), resulting in H<sub>2</sub>O. The NH<sub>3</sub> gains
the transferred proton, resulting in NH<sub>4</sub><sup>+</sup>.
We call H<sub>3</sub>O<sup>+</sup> the proton donor, or acid. We call
NH<sub>3</sub> the proton acceptor, or base.</p>
<br>
The Bronsted-Lowery concept defines something as either an acid or base
depending on its function in the acid-base (proton transfer) reaction.
Some
things can act as either an acid or a base. These are called amphiprotic
species, they can either lose or gain a proton, depending on the other
reactant.
An example of an amphiprotic species would be
HCO<sub>3</sub><sup>-</sup>. In the presence of OH<sup>-</sup>, it acts
as
an acid. In the presence of HF it acts as a base. Water is also
amphiprotic, as are most anions with ionizable hydrogens and certain
solvents. Water as an amphiprotic species is very important to the
acid-base reactions.</p>
<br>
<p>In the Bronsted-Lowery concept we have found that:</p>
<br>
<p>1. A base is a species that accepts protons, while an acid is a species
that dontates protons.</p>
<p>2. Acids and bases can be ions as well as molecular substances.</p>
<p>3. Some species can act as either acids or bases, depending on what the
other reactant is.</p>
<br>
<!--msthemeseparator--><p align="center"><img src="../../../../_themes/education/blrule.gif" width="600" height="10"></p>
<center>
<a href="#arr">Arrhenius Concept of Acids and Bases</a> |
<a href="#bl">Bronsted-Lowery Concept of Acids and Bases</a> |
<a href="#lewis">Lewis Concept of Acids and Bases</a> |
<a href="#equil">Equilibrium with Acids and Bases</a> |
<a href="#top">Top of Page</a>
</center>
<!--msthemeseparator--><p align="center"><img src="../../../../_themes/education/blrule.gif" width="600" height="10"></p>
<a name="lewis"></a>
<center>
<h2><!--mstheme--><font color="#0033CC">Lewis Concept of Acids and Bases<!--mstheme--></font></h2>
</center>
<p>The Lewis concept of acids is generalized to include reactions of
acidic
and basic oxides and many other reactions. A Lewis acid is something that
can form a covalent bond by accepting an electron air from another
species. A Lewis base is something that can form a covalent bond by
donating an electron pair to something else. The Lewis and
Bronsted-Lowery
concepts are different ways of looking at the same chemical reactions.
Here is a reaction in which an electron pair is transferred. The proton
(H<sup>+</sup>) is electron pair acceptor, alewis acid. NH<sub>3</sub>
has a lone pair of electrons and is a Lewis Base.
<br>
<center>
<IMG src="../../media/acidbase/lewis.gif" alt="base equation" width="309" height="103" >
</center>
<br>
<br>
<center>
The pH of a solution
</center>
<br>
<p>Whether or not an aqueous solution is neutral, acidic or basic
depends on the hydrogen-ion concentration. We give the acidity of an
aqueous solution in terms of the pH. pH is defined as the negative
logarithm of the molar hydrogen-ion concentration. A pH of 7 means that a
solution is neutral. A pH of below 7 means that a solution is acidic; a pH
of above 7 means that a solution is basic.
<br>
<center>
pH = -log[H<sup>+</sup>]
</center>
<br>
<p>For example, let's say that we have a glass of frosty orange juice.
This orange juice has a hydrogen-ion concentration of 2.9 x
10<sup>-4</sup> M. What is the orange juice's pH?</p>
<br>
<br>
<center>
pH = -log[H<sup>+</sup>]
= -log[2.9 x 10<sup>-4</sup>]
=3.54
</center>
<br>
<p>The pH of this solution is less than 7 so this orange juice is acidic.
<br>
<p>We can also find pH by solving for the hydroxide-ion concentration of a
solution. The measure of the hydroxide-ion concentration is called pOH.
<br>
<center>
pOH = -log[OH<sup>-</sup>]
</center>
<br>
<p>Since we know that the pH scale goes from 0 to 14, we find that:
<br>
pH + pOH = 14
<br>
<p>Let's say that we want to find the pH of an ammonia solution that has a
hydroxide-ion concentration of 1.9 x 10<sup>-3</sup> M. We start by
finding
the pOH.
<center>
pOH = -log[1.9 x 10<sup>-3</sup>]
= 2.72
<br>
</center>
<p>Now we want to find the pH by subtracting:
<center>
<br>
pH = 14.00 - pOH
= 14.00 - 2.72
= 11.28
</center>
<!--msthemeseparator--><p align="center"><img src="../../../../_themes/education/blrule.gif" width="600" height="10"></p>
<center>
<a href="#arr">Arrhenius Concept of Acids and Bases</a> |
<a href="#bl">Bronsted-Lowery Concept of Acids and Bases</a> |
<a href="#lewis">Lewis Concept of Acids and Bases</a> |
<a href="#equil">Equilibrium with Acids and Bases</a> |
<a href="#top">Top of Page</a>
</center>
<!--msthemeseparator--><p align="center"><img src="../../../../_themes/education/blrule.gif" width="600" height="10"></p>
<a name="equil"></a>
<center>
<h2><!--mstheme--><font color="#0033CC">Equilibrium with Acids and Bases<!--mstheme--></font></h2>
</center>
<p>Have you read the section about equilibrium yet? If you haven't this
most likely won't make any sense to you. If you have, lets join in on the
fun of acid-base equilibrium.
<p>Remember K<sub>c</sub> from the equilibrium section? It's back, and
more useful than ever. Now to distinguish between the K<sub>c</sub> of
acids and bases we use K<sub>a</sub> and K<sub>b</sub>. (a for acids and
b for bases) The equilibrium that is calculated in acids is usually the
disaccociation of the H<sup>+</sup> ions and the rest of the molecule.
The
weak acids and bases are the only ones that have K<sub>a</sub>'s and
K<sub>b</sub>'s because in the strong acids dissociation is very close to
100%.
<p>
<!--mstheme--></font><table border=1 bordercolordark="#000000" bordercolorlight="#000000">
<caption>Table of K<sub>a</sub>'s</caption>
<tr>
<th><!--mstheme-->Substance<!--mstheme--></font></th>
<th><!--mstheme-->Formula<!--mstheme--></font></th>
<th><!--mstheme-->K<sub>a</sub><!--mstheme--></font></th>
</tr>
<tr>
<td><!--mstheme-->Acetic Acid<!--mstheme--></font></td>
<td><!--mstheme-->HC<sub>2</sub>H<sub>3</sub>O<sub>2</sub><!--mstheme--></font></td>
<td><!--mstheme-->1.7 x 10<sup>-5</sub><!--mstheme--></font></td>
</tr>
<tr>
<td><!--mstheme-->Benzoic Acid<!--mstheme--></font></td>
<td><!--mstheme-->HC<sub>7</sub>H<sub>5</sub>O<sub>2</sub><!--mstheme--></font></td>
<td><!--mstheme-->6.3 x 10<sup>-5</sup><!--mstheme--></font></td>
</tr>
<tr>
<td><!--mstheme-->Boric Acid<!--mstheme--></font></td>
<td><!--mstheme-->H<sub>3</sub>BO<sub>3</sub><!--mstheme--></font></td>
<td><!--mstheme-->5.9 x 10<sup>-10</sup><!--mstheme--></font></td>
</tr>
<tr>
<td><!--mstheme-->Carbonic Acid<!--mstheme--></font></td>
<td><!--mstheme-->H<sub>2</sub>CO<sub>3</sub><!--mstheme--></font></td>
<td><!--mstheme-->4.3 x 10<sup>-7</sup>
</tr>
<tr>
<td><!--mstheme--><!--mstheme--></font></td>
<td><!--mstheme-->HCO<sub>3</sub><sup>-</sup><!--mstheme--></font></td>
<td><!--mstheme-->4.8 x 10<sup>-11</sup><!--mstheme--></font></td>
</tr>
<tr>
<td><!--mstheme-->Cyanic Acid<!--mstheme--></font></td>
<td><!--mstheme-->HCNO<!--mstheme--></font></td>
<td><!--mstheme-->3.5 x 10<sup>-4</sup>
</tr>
<tr>
<td><!--mstheme-->Formic Acid<!--mstheme--></font></td>
<td><!--mstheme-->HCNO<sub>2</sub><!--mstheme--></font></td>
<td><!--mstheme-->1.7 x 10<sup>-4</sup><!--mstheme--></font></td>
</tr>
<tr>
<td><!--mstheme-->Hydrocyanic Acid<!--mstheme--></font></td>
<td><!--mstheme-->HCN<!--mstheme--></font></td>
<td><!--mstheme-->4.9 x 10<sup>-10</sup><!--mstheme--></font></td>
</tr>
<tr>
<td><!--mstheme-->Hydrofluric Acid<!--mstheme--></font></td>
<td><!--mstheme-->HF<!--mstheme--></font></td>
<td><!--mstheme-->6.8 x 10<up>-4</sup><!--mstheme--></font></td>
</tr>
<tr>
<td><!--mstheme-->Hydrogen Sulfate ion<!--mstheme--></font></td>
<td><!--mstheme-->HSO<sub>4</sub><sup>-</sup><!--mstheme--></font></td>
<td><!--mstheme-->1.1 x 10<sup>-2</sup><!--mstheme--></font></td>
</tr>
<tr>
<td><!--mstheme-->Hydrogen Sulfide<!--mstheme--></font></td>
<td><!--mstheme-->H<sub>2</sub>S<!--mstheme--></font></td>
<td><!--mstheme-->8.9 x 10<sup>-8</sup><!--mstheme--></font></td>
</tr>
<tr>
<td><!--mstheme--><!--mstheme--></font></td>
<td><!--mstheme-->HS<sup>-</sup><!--mstheme--></font></td>
<td><!--mstheme-->1.2 x 10<sup>-13</sup><!--mstheme--></font></td>
</tr>
<tr>
<td><!--mstheme-->Hypochlorous acid<!--mstheme--></font></td>
<td><!--mstheme-->HClO<!--mstheme--></font></td>
<td><!--mstheme-->3.5 x 10<sup>-8</sup><!--mstheme--></font></td>
</tr>
<tr>
<td><!--mstheme-->Nitrous Acid<!--mstheme--></font></td>
<td><!--mstheme-->HNO<sub>2</sub><!--mstheme--></font></td>
<td><!--mstheme-->4.5 x 10<sup>-4</sup><!--mstheme--></font></td>
</tr>
<tr>
<td><!--mstheme-->Oxalic Acid<!--mstheme--></font></td>
<td><!--mstheme-->H<sub>2</sub>C<sub>2</sub>O<sub>4</sub><!--mstheme--></font></td>
<td><!--mstheme-->5.6 x 10<sup>-2</sup>
</tr>
<tr>
<td><!--mstheme--><!--mstheme--></font></td>
<td><!--mstheme-->HC<sub>2</sub>O<sub>4</sub><sup>-</sup><!--mstheme--></font></td>
<td><!--mstheme-->5.1 x 10<sup>-5</sup><!--mstheme--></font></td>
</tr>
<tr>
<td><!--mstheme-->Phosphoric Acid<!--mstheme--></font></td>
<td><!--mstheme-->H<sub>3</sub>PO<sub>4</sub><!--mstheme--></font></td>
<td><!--mstheme-->6.9 x 10<sup>-3</sup><!--mstheme--></font></td>
</tr>
<tr>
<td><!--mstheme--><!--mstheme--></font></td>
<td><!--mstheme-->H<sub>2</sub>PO<sub>4</sub><sup>-</sup><!--mstheme--></font></td>
<td><!--mstheme-->6.2 x 10<sup>-8</sup><!--mstheme--></font></td>
</tr>
<tr>
<td><!--mstheme--><!--mstheme--></font></td>
<td><!--mstheme-->HPO<sub>4</sub><sup>-2</sup><!--mstheme--></font></td>
<td><!--mstheme-->4.8 x 10<sup>-13</sup><!--mstheme--></font></td>
</tr>
<tr>
<td><!--mstheme-->Phosphorous Acid<!--mstheme--></font></td>
<td><!--mstheme-->H<sub>2</sub>PHO<sub>3</sub><!--mstheme--></font></td>
<td><!--mstheme-->1.6 x 10<sup>-2</sup><!--mstheme--></font></td>
</tr>
<tr>
<td><!--mstheme--><!--mstheme--></font></td>
<td><!--mstheme-->HPHO<sub>3</sub><sup>-</sup><!--mstheme--></font></td>
<td><!--mstheme-->7 x 10<sup>-7</sup><!--mstheme--></font></td>
</tr>
<tr>
<td><!--mstheme-->Propionic Acid<!--mstheme--></font></td>
<td><!--mstheme-->HC<sub>3</sub>H<sub>5</sub>O<sub>2</sub><!--mstheme--></font></td>
<td><!--mstheme-->1.3 x 10<sup>-5</sup><!--mstheme--></font></td>
</tr>
<tr>
<td><!--mstheme-->Pyruvic Acid<!--mstheme--></font></td>
<td><!--mstheme-->HC<sub>3</sub>H<sub>3</sub>O<sub>3</sub><!--mstheme--></font></td>
<td><!--mstheme-->1.4 x 10<sup>-4</sup><!--mstheme--></font></td>
</tr>
<tr>
<td><!--mstheme-->Sulfurous Acid<!--mstheme--></font></td>
<td><!--mstheme-->H<sub>2</sub>SO<sub>3</sub><!--mstheme--></font></td>
<td><!--mstheme-->1.3 x 10<sup>-2</sup><!--mstheme--></font></td>
</tr>
<tr>
<td><!--mstheme--><!--mstheme--></font></td>
<td><!--mstheme-->HSO<sub>3</sub><sup>-</sup><!--mstheme--></font></td>
<td><!--mstheme-->6.3 x 10<sup>-8</sup><!--mstheme--></font></td>
</tr>
</table><!--mstheme-->
<p>The base K<sub>b</sub>'s are as follows:
<!--mstheme--></font><table border=1 bordercolordark="#000000" bordercolorlight="#000000">
<tr>
<th><!--mstheme-->Substance<!--mstheme--></font></th>
<th><!--mstheme-->Formula<!--mstheme--></font></th>
<th><!--mstheme-->K<sub>b</sub><!--mstheme--></font></th>
</tr>
<tr>
<td><!--mstheme-->Ammonia<!--mstheme--></font></td>
<td><!--mstheme-->NH<sub>3</sub><!--mstheme--></font></td>
<td><!--mstheme-->1.8 x 10<sup>-5</sup><!--mstheme--></font></td>
</tr>
<tr>
<td><!--mstheme-->Aniline<!--mstheme--></font></td>
<td><!--mstheme-->C<sub>6</sub>H<sub>5</sub>NH<sub>2</sub><!--mstheme--></font></td>
<td><!--mstheme-->4.2 x 10<sup>-10</sup><!--mstheme--></font></td>
</tr>
<tr>
<td><!--mstheme-->Dimethylamine<!--mstheme--></font></td>
<td><!--mstheme-->(CH<sub>3</sub>)<sub>3</sub>NH<!--mstheme--></font></td>
<td><!--mstheme-->5.1 x 10<sup>-4</sup><!--mstheme--></font></td>
</tr>
<tr>
<td><!--mstheme-->Ethylamine<!--mstheme--></font></td>
<td><!--mstheme-->C<sub>2</sub>H<sub>5</sub>NH<sub>2</sub><!--mstheme--></font></td>
<td><!--mstheme-->4.7 x 10<sup>-4</sup><!--mstheme--></font></td>
</tr>
<tr>
<td><!--mstheme-->Hydrazine<!--mstheme--></font></td>
<td><!--mstheme-->N<sub>2</sub>H<sub>4</sub><!--mstheme--></font></td>
<td><!--mstheme-->1.7 x 10<sup>-6</sup><!--mstheme--></font></td>
</tr>
<tr>
<td><!--mstheme-->Hydroxylamine<!--mstheme--></font></td>
<td><!--mstheme-->NH<sub>2</sub>OH<!--mstheme--></font></td>
<td><!--mstheme-->1.1 x 10<sup>-8</sup><!--mstheme--></font></td>
</tr>
<tr>
<td><!--mstheme-->Methylamine<!--mstheme--></font></td>
<td><!--mstheme-->CH<sub>3</sub>NH<sub>2</sub><!--mstheme--></font></td>
<td><!--mstheme-->4.4 x 10<sup>-4</sup><!--mstheme--></font></td>
</tr>
<tr>
<td><!--mstheme-->Pyridine<!--mstheme--></font></td>
<td><!--mstheme-->C<sub>5</sub>H<sub>5</sub>N<!--mstheme--></font></td>
<td><!--mstheme-->1.4 x 10<sup>-9</sup><!--mstheme--></font></td>
</tr>
<tr>
<td><!--mstheme-->Urea<!--mstheme--></font></td>
<td><!--mstheme-->NH<sub>2</sub>CONH<sub>2</sub><!--mstheme--></font></td>
<td><!--mstheme-->1.5 x 10<sup>-14</sup><!--mstheme--></font></td>
</tr>
</table><!--mstheme-->
<h3><!--mstheme--><font color="#6666CC">Examples<!--mstheme--></font></h3>
<p><h3><!--mstheme--><font color="#6666CC">Weak Acid Example:<!--mstheme--></font></h3>
<p>Calculate the pH of a 0.100 M solution of HClO
<center>
<!--mstheme--></font><table border=0>
<tr>
<td><!--mstheme-->HClO<!--mstheme--></font></td> <td><!--mstheme--><--><!--mstheme--></font></td> <td><!--mstheme-->H<sup>+</sup><!--mstheme--></font></td> <td><!--mstheme-->+<!--mstheme--></font></td>
<td><!--mstheme-->ClO<sup>-</sup><!--mstheme--></font></td>
</tr>
<tr>
<td align=center><!--mstheme-->.100 - x<!--mstheme--></font></td>
<td><!--mstheme--><!--mstheme--></font></td>
<td align=center><!--mstheme-->x<!--mstheme--></font></td>
<td><!--mstheme--><!--mstheme--></font></td>
<td align=center><!--mstheme-->x<!--mstheme--></font></td>
</tr>
</table><!--mstheme-->
</center>
<!--mstheme--></font><table border=0>
<tr>
<td rowspan=2><!--mstheme-->K<sub>a</sub> = <!--mstheme--></font></td><td
align=center><!--mstheme-->__<u>x<sup>2</sup></u>__<!--mstheme--></font></td>
</tr>
<tr>
<td><!--mstheme-->.100 - x<!--mstheme--></font></td>
</tr>
</table><!--mstheme-->
<p>The x in the denominator can be dropped because K<sub>a</sub>/M is
less than
10<sup>-3</sup>. If K<sub>a</sub>/M is greater than 10<sup>-3</sup> you
have to use the
quadratic formula to solve the equation.
<p>Therefore:
<!--mstheme--></font><table border=0>
<tr>
<td rowspan=2><!--mstheme-->3.5 x 10<sup>-8</sup> = <!--mstheme--></font></td><td
align=center><!--mstheme-->__<u>x<sup>2</sup></u>__<!--mstheme--></font></td>
</tr>
<tr>
<td><!--mstheme-->.100<!--mstheme--></font></td>
</tr>
</table><!--mstheme-->
<p>3.5 x 10<sup>-9</sup> = x<sup>2</sup>
<p>x = 5.9 x 10<sup>-5</sup>
<p>
[H<sup>+</sup>] = 5.9 x 10<sup>-5</sup> M<br>
[ClO<sup>-</sup>] = 5.9 x 10<sup>-5</sup> M<br>
[HClO] = .100 M - 5.9 x 10<sup>-5</sup> ~= .100 M
<p>pH = -log(5.9 x 10<sup>-5</sup>) = 4.2
<h3><!--mstheme--><font color="#6666CC"><p>Weak Base Example:<!--mstheme--></font></h3>
<p>What is the concentration of OH<sup>-</sup> of a .20 molar solution
of aniline?
<!--mstheme--></font><table border=0>
<tr>
<td><!--mstheme-->C<sub>6</sub>H<sub>5</sub>NH<sub>2</sub><!--mstheme--></font></td> <td><!--mstheme--><--> <!--mstheme--></font></td>
<td><!--mstheme-->C<sub>6</sub>H<sub>5</sub>NH<sub>3</sub><sup>+</sup><!--mstheme--></font></td> <td><!--mstheme-->+<!--mstheme--></font></td>
<td><!--mstheme-->OH<sup>-</sup><!--mstheme--></font></td>
</tr>
<tr>
<td align=center><!--mstheme-->.20 - x<!--mstheme--></font></td>
<td><!--mstheme--><!--mstheme--></font></td>
<td align=center><!--mstheme-->x<!--mstheme--></font></td>
<td><!--mstheme--><!--mstheme--></font></td>
<td align=center><!--mstheme-->x<!--mstheme--></font></td>
</tr>
</table><!--mstheme-->
<!--mstheme--></font><table border=0>
<tr>
<td rowspan=2><!--mstheme-->K<sub>b</sub> = <!--mstheme--></font></td>
<td align=center><!--mstheme-->__<u>x<sup>2</sup></u>__<!--mstheme--></font></td>
</tr>
<tr>
<td><!--mstheme-->.20 - x<!--mstheme--></font></td>
</tr>
</table><!--mstheme-->
<p>The x in the denominator can be dropped because K<sub>b</sub>/M is less
than
10<sup>-3</sup>. If K<sub>b</sub>/M is greater than 10<sup>-3</sup> you
have to use the
quadratic formula to solve the equation.
<p>Therefore:
<!--mstheme--></font><table border=0>
<tr>
<td rowspan=2><!--mstheme-->K<sub>b</sub> = <!--mstheme--></font></td>
<td align=center><!--mstheme-->__<u>x<sup>2</sup></u>__<!--mstheme--></font></td>
</tr>
<tr>
<td><!--mstheme-->.20<!--mstheme--></font></td>
</tr>
</table><!--mstheme-->
<p>x<sup>2</sup> = 8.4 x 10<sup>-11</sup>
<p>x = 9.2 x 10<sup>-6</sup>
<p>[OH<sup>-</sup>] = 9.2 x 10<sup>-6</sup>
<!--msthemeseparator--><p align="center"><img src="../../../../_themes/education/blrule.gif" width="600" height="10"></p>
<center>
<a href="#arr">Arrhenius Concept of Acids and Bases</a> |
<a href="#bl">Bronsted-Lowery Concept of Acids and Bases</a> |
<a href="#lewis">Lewis Concept of Acids and Bases</a> |
<a href="#equil">Equilibrium with Acids and Bases</a> |
<a href="#top">Top of Page</a> | <a href="../../index.html">Home</a> | <a href="../search.htm">Search</a> |
<a href="../../glossary.htm">Main Glossary</a>
</center>
<!--msthemeseparator--><p align="center"><img src="../../../../_themes/education/blrule.gif" width="600" height="10"></p>
<!--mstheme--></font></body>
]]>