Last reminders:
This week (Dead Week) is your last chance at:
SI
Office hours
Most semester exam, homework
and extracredit grade issues
If there are grade issues on Exam 4, I am
willing to address those issues until 2:30 PM on
Monday, April 27.
Last reminders:
Final exam time scheduled by university:
CH101002 (MWF 11:20
–
12:10)
Monday, May 4, 811 AM DAB222
Per university regulation, students must take
their final exam during the section they are
REGISTERED for.
The only reason for an exam
time change is three exams in 24 hours.
pH and pKa
pH:
log
[H
3
O
1+
]
pK
a
:
log
[K
a
]
Section 12.9
Acid Dissociation Constant
HA (aq) + H
2
O (l)
A
1
(aq) + H
3
O
1+
(aq)
K
=
The stronger the acid the more the
product side is favored,
i.e.,
the bigger the K
a
, the larger the [H
3
O
1+
],
and the smaller the pK
a
[A
1
][H
3
O
1+
]
[HA]
a
pH and pKa
pH:
log
[H
3
O
1+
]
pK
a
:
log
[K
a
]
A variable quantity:
HIGHLY dependent upon
both
concentration
and
the
strength of the acid/
base
used.
A fixed quantity:
Inherent
to the
acid/
base
used.
Section 12.9
In base 10, the log is simply the exponent.
pH = log
[H
3
O
1+
]
What is log?
log 10
3
= ___
3
Section 12.9
log(0.0001) = log(1 x 10
4
) = 4
on a TI=83+, type in “(

)” “LOG” “1” “2
nd
” “EE” “(

)” “4”
log(0.0025) = log(2.5 x 10
3
) = 2.60
on a TI=83+, type in “(

)” “LOG” “2.5” “2
nd
” “EE” “(

)” “3”
What is the pH when [H
3
O
1+
] =
0.000001?
1. 6
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 Fall '08
 BIGHAM
 Mole, pH, H3O1+

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