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4HClO2 ๐Ÿ”ฅ|๐Ÿ•’โ†’ 2ClO2โ†‘ + Cl2โ†‘ + 2H2O2

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Decomposition of chlorous acid
4HClO2Chlorous acid
๐Ÿ”ฅ|๐Ÿ•’
โŸถ
2ClO2โ†‘Chlorine dioxide + Cl2โ†‘Chlorine + 2H2O2Hydrogen peroxide

Decomposition of chlorous acid yields chlorine dioxide, chlorine, and hydrogen peroxide (Other reactions are here). This reaction is an oxidation-reduction reaction and is classified as follows:

Table of contents
  1. 1Reaction data
  2. 2Thermodynamic changes
  3. 3References
  4. 4Related reactions
  5. 5Related categories

Reaction data

Chemical equation

Decomposition of chlorous acid
4HClO2Chlorous acid
๐Ÿ”ฅ|๐Ÿ•’
โŸถ
2ClO2โ†‘Chlorine dioxide + Cl2โ†‘Chlorine + 2H2O2Hydrogen peroxide

General equation

Thermal decomposition with redox
Thermally decomposable substanceSelf redox agent
๐Ÿ”ฅ
โŸถ
ProductOxidation product + ProductReduction product
Spontaneous decomposition with redox
Spontaneously decomposable substanceSelf redox agent
๐Ÿ•’
โŸถ
ProductOxidation product + ProductReduction product

Oxidation state of each atom

Decomposition of chlorous acid

Reactants

Chemical formulaNameCoefficientTypeType in general
equation
HClO2Chlorous acid4
Reducing
Thermally decomposable
Spontaneously decomposable

Products

Chemical formulaNameCoefficientTypeType in general
equation
ClO2Chlorine dioxide2
Oxidized
โ€“
Cl2Chlorine1
Reduced
โ€“
H2O2Hydrogen peroxide2
Oxidized
โ€“

Thermodynamic changes

Changes in standard condition (1)

Decomposition of chlorous acid
โ—†
ฮ”rGโˆ’50.7 kJ/mol
K7.63 ร— 108
pKโˆ’8.88
4HClO2Un-ionized aqueous solution
๐Ÿ”ฅ|๐Ÿ•’
โŸถ
2ClO2โ†‘Gas + Cl2โ†‘Gas + 2H2O2Un-ionized aqueous solution
Standard enthalpy
of reaction
ฮ”rHยฐ
kJ ยท molโˆ’1		Standard
Gibbs energy
of reaction
ฮ”rGยฐ
kJ ยท molโˆ’1		Standard entropy
of reaction
ฮ”rSยฐ
J ยท Kโˆ’1 ยท molโˆ’1		Standard heat
capacity of reaction
at constant pressure
ฮ”rCpยฐ
J ยท Kโˆ’1 ยท molโˆ’1
per 1 mol of
Equation
30.3โˆ’50.7271.3โ€“
per 1 mol of
7.58โˆ’12.767.83โ€“
per 1 mol of
15.2โˆ’25.4135.7โ€“
per 1 mol of
30.3โˆ’50.7271.3โ€“
per 1 mol of
15.2โˆ’25.4135.7โ€“

Changes in standard condition (2)

Decomposition of chlorous acid
โ—†
ฮ”rGโˆ’43.7 kJ/mol
K4.53 ร— 107
pKโˆ’7.66
4HClO2Un-ionized aqueous solution
๐Ÿ”ฅ|๐Ÿ•’
โŸถ
2ClO2โ†‘Gas + Cl2โ†‘Un-ionized aqueous solution + 2H2O2Un-ionized aqueous solution
Standard enthalpy
of reaction
ฮ”rHยฐ
kJ ยท molโˆ’1		Standard
Gibbs energy
of reaction
ฮ”rGยฐ
kJ ยท molโˆ’1		Standard entropy
of reaction
ฮ”rSยฐ
J ยท Kโˆ’1 ยท molโˆ’1		Standard heat
capacity of reaction
at constant pressure
ฮ”rCpยฐ
J ยท Kโˆ’1 ยท molโˆ’1
per 1 mol of
Equation
6.9โˆ’43.7169โ€“
per 1 mol of
1.7โˆ’10.942.3โ€“
per 1 mol of
3.5โˆ’21.984.5โ€“
per 1 mol of
6.9โˆ’43.7169โ€“
per 1 mol of
3.5โˆ’21.984.5โ€“

Changes in standard condition (3)

Decomposition of chlorous acid
โ—†
ฮ”rGโˆ’51.5 kJ/mol
K1.05 ร— 109
pKโˆ’9.02
4HClO2Un-ionized aqueous solution
๐Ÿ”ฅ|๐Ÿ•’
โŸถ
2ClO2โ†‘Un-ionized aqueous solution + Cl2โ†‘Gas + 2H2O2Un-ionized aqueous solution
Standard enthalpy
of reaction
ฮ”rHยฐ
kJ ยท molโˆ’1		Standard
Gibbs energy
of reaction
ฮ”rGยฐ
kJ ยท molโˆ’1		Standard entropy
of reaction
ฮ”rSยฐ
J ยท Kโˆ’1 ยท molโˆ’1		Standard heat
capacity of reaction
at constant pressure
ฮ”rCpยฐ
J ยท Kโˆ’1 ยท molโˆ’1
per 1 mol of
Equation
โˆ’24.9โˆ’51.587.3โ€“
per 1 mol of
โˆ’6.22โˆ’12.921.8โ€“
per 1 mol of
โˆ’12.4โˆ’25.843.6โ€“
per 1 mol of
โˆ’24.9โˆ’51.587.3โ€“
per 1 mol of
โˆ’12.4โˆ’25.843.6โ€“

Changes in standard condition (4)

Decomposition of chlorous acid
โ—†
ฮ”rGโˆ’44.5 kJ/mol
K6.25 ร— 107
pKโˆ’7.80
4HClO2Un-ionized aqueous solution
๐Ÿ”ฅ|๐Ÿ•’
โŸถ
2ClO2โ†‘Un-ionized aqueous solution + Cl2โ†‘Un-ionized aqueous solution + 2H2O2Un-ionized aqueous solution
Standard enthalpy
of reaction
ฮ”rHยฐ
kJ ยท molโˆ’1		Standard
Gibbs energy
of reaction
ฮ”rGยฐ
kJ ยท molโˆ’1		Standard entropy
of reaction
ฮ”rSยฐ
J ยท Kโˆ’1 ยท molโˆ’1		Standard heat
capacity of reaction
at constant pressure
ฮ”rCpยฐ
J ยท Kโˆ’1 ยท molโˆ’1
per 1 mol of
Equation
โˆ’48.3โˆ’44.5โˆ’15โ€“
per 1 mol of
โˆ’12.1โˆ’11.1โˆ’3.8โ€“
per 1 mol of
โˆ’24.1โˆ’22.3โˆ’7.5โ€“
per 1 mol of
โˆ’48.3โˆ’44.5โˆ’15โ€“
per 1 mol of
โˆ’24.1โˆ’22.3โˆ’7.5โ€“

Thermodynamic data of reactants

Chemical formulaStandard enthalpy
of formation
ฮ”fHยฐ
kJ ยท molโˆ’1		Standard Gibbs
energy of
formation
ฮ”fGยฐ
kJ ยท molโˆ’1		Standard
molar entropy
Sยฐ
J ยท Kโˆ’1 ยท molโˆ’1		Standard molar
heat capacity at
constant pressure
Cpยฐ
J ยท Kโˆ’1 ยท molโˆ’1
HClO2 (ao)-51.9[1]5.9[1]188.3[1]โ€“
* (ao):Un-ionized aqueous solution

Thermodynamic data of products

Chemical formulaStandard enthalpy
of formation
ฮ”fHยฐ
kJ ยท molโˆ’1		Standard Gibbs
energy of
formation
ฮ”fGยฐ
kJ ยท molโˆ’1		Standard
molar entropy
Sยฐ
J ยท Kโˆ’1 ยท molโˆ’1		Standard molar
heat capacity at
constant pressure
Cpยฐ
J ยท Kโˆ’1 ยท molโˆ’1
ClO2 (g)102.5[1]120.5[1]256.84[1]41.97[1]
ClO2 (ao)74.9[1]120.1[1]164.8[1]โ€“
Cl2 (g)0[1]0[1]223.066[1]33.907[1]
Cl2 (ao)-23.4[1]6.94[1]121[1]โ€“
H2O2 (l)-187.78[1]-120.35[1]109.6[1]89.1[1]
H2O2 (g)-136.31[1]-105.57[1]232.7[1]43.1[1]
H2O2 (ao)-191.17[1]-134.03[1]143.9[1]โ€“
* (g):Gas, (ao):Un-ionized aqueous solution, (l):Liquid

References

List of references

  1. 1
    Janiel J. Reed (1989)
    The NBS Tables of Chemical Thermodynamic Properties: Selected Values for Inorganic and C1 and C2 Organic Substances in SI Units
    National Institute of Standards and Technology (NIST)