Chemistry Reference
In-Depth Information
(a)
14.0
12.0
10.0
8.0
Fe(V)
6.0
Fe
IV
O
2+
4.0
Fe(VI)
2.0
0.0
200
220
240
260
280
300
320
340
λ
(nm)
(b)
1200
Fe(IV)
F
e(VI)
1000
800
F
e(V)
600
400
200
400
450
500
550
600
650
700
λ
(nm)
Figure 6.24.
Spectra of iron(IV), iron(V), and iron(VI) in uV (a) and visible (b) wave-
length regions.
The ferryl ion also reacts with hydrogen peroxide to first form HO
2
, which
in turn reacts with another ferryl ion to produce oxygen [321] (reactions 6.88
and 6.89). The formation of HO
2
by a 1 − e
−
transfer is supported by the agree-
ment between the experimental and the predicted values of the rate constants
from the linear relationship between log
k
versus
E
o
(H
2
O
2
/HO
2
) (Fig. 6.25).
The rate constants for the reactions between FeO
2+
and various inorganic
ions are presented in Table 6.4. The rate constants ranged from 1 × 10
2
/M/s to
1.8 × 10
5
/M/s. A linear relationship between log
k
and the standard 1 − e
−
redox potential,
E
o
, was observed (Fig. 6.25), suggesting electron transfer reac-
tions [321] (e.g., reactions 6.92 and 6.93):
2
+
3
+
−
(6.92)
FeO
+
HNO
→
Fe
+
NO OH
+
2
2
2
+
2
+
+
3
+
3
+
.
(6.93)
FeO Mn
+
+
2
H
→
Fe Mn
+
+
H O
2
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