Chemistry Reference
In-Depth Information
[BH
]
[OH
]
K
b
———-------
[B]
where
K
b
is termed the base dissociation constant or basicity constant.
a
2
c
K
b
——--
(1
a
)
As before
a
is very small and can be neglected, so (1
a
) is approximately
1.
K
b
a
2
—
c
(
—
)
K
b
a
c
From above,
[OH
]
ca
Therefore,
(
—
)
(
K
b
c
)
K
b
[OH
]
c
c
However,
K
w
[H
]
[OH
]
Therefore,
K
w
—--
(
K
b
c
)
[H
]
and
K
w
[H
]
—---
(
K
b
c
)
Taking logarithms,
log
K
w
4
log
K
b
4
log[H
]
log
c
or
p
K
w
5
p
K
b
5
pH
log
c
(1.3)
