1
See Sparks, 2003; Evangelou,
1998; or Essington, 2004 or
http://www.khanacademy.org
Assorted videos on acidbase,
buffers, pKa, and Henderson
Hasselbalch eqn
pKa concepts
Ionization = the process in which ions are formed
from neutral compounds;
Dissociation = the separation of the ions of an
electrovalent compound as a result of the action
of a solvent (usually water)
For a weak acid, which dissociates as follows:
HA
↔
H
+
+ A

An interesting and extremely useful relationship between
pH and pK
a
can be obtained simply by taking logarithms
(to the base 10) of the previous equation:
log
10
K
a
= log
10
[H
+
] + log
10
[A

]  log
10
[HA]
Rearranging:
log
10
[H
+
] = log
10
K
a
+ log
10
[A

]  log
10
[HA]
Note: log a
–
log b = log (a/b); px = log[x]
giving the
HendersonHasselbalch
equation
:
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