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Halogenous acid and its salt
Halogenous acid HXO 2 , halogen as the central atom adopts sp 3 hybridization, and the molecular configuration is V-shaped
.
1.
Preparation
HCIO 2 can be prepared by reacting halide with acid
.
Ba(ClO 2 ) 2 +H 2 SO 4 =2HCIO 2 +BaSO 4
Use of the CIO 2 reaction with peroxide may also be prepared chlorite
2C1O 2 +BaO 2 =Ba(ClO 2 ) 2 +O 2
2.
Nature
Among the haloacids , only chlorous acid HCIO 2 can exist in the form of a dilute solution, but it is also extremely unstable and decomposes quickly to produce ClO 2 , which makes the solution yellow
.
8HCIO 2 =6ClO 2 +Cl 2 +4H 2 O
Chlorite Although Shakespeare acid stable, but easy disproportionation reaction when exposed to heat or collision
.
3NaClO 2 = 2NaClO 3 +NaCl
The aqueous solution of chlorite has strong oxidizing properties and is mainly used for bleaching fabrics
.
Halogen acids and their salts
Halogen acid HXO 3 , halogen as the central atom adopts sp 3 hybridization, and the molecular configuration is triangular cone
.
1.
Preparation
Halogen element disproportionation in alkaline aqueous solution can produce halide salt
.
3X 2 + 6OH - = 5X - + the XO .
3 - + 3H 2 O
The disadvantage of this method is that the utilization rate of the reactants is too low
.
Bromate and iodate can be prepared by oxidation of elemental substances with strong oxidants
.
Br 2 + 3Cl 2 + 6OH - = BrO .
3 - + 6Cl - + 3H 2 O
I 2 +10HNO (concentrated) = 2HIO 3 + 10NO 2 +4H 2 O
In the laboratory, the aqueous solution of halogen acid is prepared by the action of halogen acid salt and sulfuric acid.
The concentration of sulfuric acid in the reaction should not be too high, otherwise the product HXO 3 concentration is too high and explosive decomposition may occur
.
Ba(XO 3 ) 2 +H 2 SO 4 =2HXO 3 +BaSO 4
2.
Nature
Halogen acids are strong acids, and the acidity is weaker in order of HCIO 3 , HBrO 3 , and HIO 3
.
The stability of halogen acid is higher than that of hypohalous acid, and HIO 3 has the highest stability and exists in solid form
.
However, HCIO 3 and HBrO 3 only exist in the aqueous solution.
8HC1O 3 =4HCIO 4 +2Cl 2 +3O 2 +2H 2 O
4HBrO 3 =2Br 2 +5O 2 +2H 2 O
The thermal stability of halogen acid salt is higher than that of the corresponding acid, but it also decomposes when heated
.
Common halide salts have KCIO 3 , Nalo 3 and so on
4KCIO 3 =3KCIO 4 +KCI
Under the action of the catalyst, KCIO 3 is heated and decomposed to generate KCl and O 2
.
2KCIO 3 =2KCl+3O 2
The thermal stability of oxyacids and their salts can be explained by the theory of ion polarization
.
Due to the extremely strong polarizing ability of H+, oxygen-containing acids have lower thermal stability than their salts
Both halogen acids and their salts have strong oxidizing properties
.
5HCIO 3 +6 P+9H 2 O=6H 3 PO 4 +5HCl
HCIO 3 +S+H 2 O=H 2 SO 4 +HCI
5HCIO 3 +3I 2 +3H 2 O=6HIO 3 +5HCI
If HCIO 3 is excessive, Cl 2 will be formed in the product
.
KCIO 3 solid is mixed with concentrated hydrochloric acid, and the characteristic yellow CIO 2 is produced
.
8KCIO 3 +24HCI (concentrated)=9Cl 2 +8KCl+6ClO 2 +12H 2 O
Among the three halogen acids, the most oxidizing is HBrO 3 , and the weakest is HIO 3
.
The oxidizability of halogen oxyacids is related to the stability.
HCIO>HCIO 3 >HCIO 4
Under alkaline conditions, KCIO can oxidize Kl, while KCIO 3 can oxidize KI under acidic conditions
