Chemistry Reference
In-Depth Information
EXAMPLE 19.10
Calculate the pH of a solution that has a hydronium ion concentration of
10
5
M.
3.5
Solution
log
[H
3
O
]
10
5
)
pH
log
(3.5
4.46
Practice Problem 19.10
Calculate the hydronium ion concentration
of a solution with a pH of 12.014.
EXAMPLE 19.11
Analogously to pH, pOH can be defined as
log
[OH
]
pOH
Show that
pH
pOH
14.00
in all dilute aqueous solutions.
Solution
All we need to do is take the logarithm of the equation for
K
w
.
(The log of a
product is the sum of the logs of the terms.)
[H
3
O
][OH
]
10
14
K
w
1.0
10
14
)
log(1.0
(
pH)
(
pOH)
14.00
Multiplying this last equation by
1
yields
pH
pOH
14.00
This equation is useful to calculate pH from pOH, and vice versa.
EXAMPLE 19.12
Calculate the hydronium ion concentration of a solution with
pH
6.429.
Solution
[H
3
O
]
10
7
M
3.72
Use three significant digits because there are three digits after the decimal point
in the value given for the pH.
Practice Problem 19.12
Calculate the hydronium ion concentration
of a solution with pH
9.44.
