Oxy-acid Salts
Table of some oxy-acid salts containing chlorine
Oxidation
State
Formula
Name
Structure
Remarks
+1
ClO
-
Hypochlorite
(monooxochlorate)
Good oxidising agent.
+3
ClO2
-
Chlorite
(dioxoxchlorate)
Strong oxidising agent
disproportionates.
+5
ClO3
-
Chlorate
(trioxochlorate)
Oxidising agent.
+7
ClO4
-
Perchlorate
(tetraoxochlorate)
Oxidising agent and
weak acid.
Fluorine containing example rare, no HFO
2
, HOF
F
2
+ H
2
O
HF + O
2
oxidation
Cl, Br, I more complex
X
2
+ H
2
O
H
+
+ X
-
+ HOX
D
G
o
>0, unfavourable for all X
So free X
2
in acid.
However, 2H
2
O
2H
+
+ 2OH
-
D
G
o
>0
X
2
+ 2OH
-
X
-
+ XO
-
+ H
2
O
D
G
o
<0, favourable for all X.
So
no
free X2 in alkali.
In OH
-
, reaction driven by neutralisation of H
+
on the Right Hand Side of the reaction in acid.
This is the common effect of the pH dependence of reaction.
In Bleach at alkaline/neutral pH ClO
-
is active ingredient, in equilibrium with Cl
2
O, give yellow colour of bleach.
A problem: further disproportionation.
2XO
-
+ 2OH
-
2X
-
+ XO
3
-
+ H
2
O
Very favourable for Cl, Br, I
BrO
-
and IO
-
which are very unstable with respect to disproportionaltion.
But ClO
-
is slow, but fast on heating to 70
o
C.
Stability of intermediate oxidation states (+3, +5) complexes, but positive
oxidation state common down the group.
HOEO
n
: acidity increases with n
HF + O2 oxidation
H+ + X- + HOX DGo>0,
unfavourable for all X
2H+ + 2OH- DGo>0
X- + XO- + H2O DGo<0,
favourable for all X.
BrO-
and IO- which are very unstable with respect to disproportionaltion.