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4KNO3 🔥→ 2K2O + 4NO2↑ + O2

Decomposition of potassium nitrate yields potassium oxide, nitrogen dioxide, and oxygen (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

General equation

Thermal decomposition with redox
Thermally decomposable substanceSelf redox agent
🔥
ProductOxidation product + ProductReduction product
Thermal decomposition of oxoacid salt with redox
Oxoacid saltSelf redox agent
🔥
ProductOxidation product + ProductReduction product

Oxidation state of each atom

Decomposition of potassium nitrate

Reactants

Chemical formulaNameCoefficientTypeType in general
equation
KNO3Potassium nitrate4
Self redox agent
Thermally decomposable
Oxoacid salt

Products

Chemical formulaNameCoefficientTypeType in general
equation
K2OPotassium oxide2
NO2Nitrogen dioxide4
Reduced
O2Oxygen1
Oxidized

Thermodynamic changes

Changes in standard condition

Decomposition of potassium nitrate
ΔrG1140.5 kJ/mol
K0.16 × 10−199
pK199.81
4KNO3Crystalline solid
🔥
2K2OCrystalline solid + 4NO2Gas + O2Gas
Standard enthalpy
of reaction
ΔrH°
kJ · mol−1
Standard
Gibbs energy
of reaction
ΔrG°
kJ · mol−1
Standard entropy
of reaction
ΔrS°
J · K−1 · mol−1
Standard heat
capacity of reaction
at constant pressure
ΔrCp°
J · K−1 · mol−1
per 1 mol of
Equation
1388.21140.5821.4−40.0
per 1 mol of
347.05285.13205.3−10.0
per 1 mol of
694.10570.25410.7−20.0
per 1 mol of
347.05285.13205.3−10.0
per 1 mol of
1388.21140.5821.4−40.0

Changes in aqueous solution (1)

Decomposition of potassium nitrate
ΔrG1139.2 kJ/mol
K0.26 × 10−199
pK199.58
4KNO3Ionized aqueous solution
🔥
2K2OCrystalline solid + 4NO2Gas + O2Gas
Standard enthalpy
of reaction
ΔrH°
kJ · mol−1
Standard
Gibbs energy
of reaction
ΔrG°
kJ · mol−1
Standard entropy
of reaction
ΔrS°
J · K−1 · mol−1
Standard heat
capacity of reaction
at constant pressure
ΔrCp°
J · K−1 · mol−1
per 1 mol of
Equation
1248.71139.2358.0605.2
per 1 mol of
312.18284.8089.50151.3
per 1 mol of
624.35569.60179.0302.6
per 1 mol of
312.18284.8089.50151.3
per 1 mol of
1248.71139.2358.0605.2

Changes in aqueous solution (2)

Decomposition of potassium nitrate
ΔrG1155.6 kJ/mol
K0.35 × 10−202
pK202.45
4KNO3Ionized aqueous solution
🔥
2K2OCrystalline solid + 4NO2Gas + O2Un-ionized aqueous solution
Standard enthalpy
of reaction
ΔrH°
kJ · mol−1
Standard
Gibbs energy
of reaction
ΔrG°
kJ · mol−1
Standard entropy
of reaction
ΔrS°
J · K−1 · mol−1
Standard heat
capacity of reaction
at constant pressure
ΔrCp°
J · K−1 · mol−1
per 1 mol of
Equation
1237.01155.6263.7
per 1 mol of
309.25288.9065.92
per 1 mol of
618.50577.80131.8
per 1 mol of
309.25288.9065.92
per 1 mol of
1237.01155.6263.7

Thermodynamic data of reactants

Chemical formulaStandard enthalpy
of formation
ΔfH°
kJ · mol−1
Standard Gibbs
energy of
formation
ΔfG°
kJ · mol−1
Standard
molar entropy
S°
J · K−1 · mol−1
Standard molar
heat capacity at
constant pressure
Cp°
J · K−1 · mol−1
KNO3 (cr)-494.63[1]-394.86[1]133.05[1]96.40[1]
KNO3 (ai)-459.74[1]-394.53[1]248.9[1]-64.9[1]
* (cr):Crystalline solid, (ai):Ionized aqueous solution

Thermodynamic data of products

Chemical formulaStandard enthalpy
of formation
ΔfH°
kJ · mol−1
Standard Gibbs
energy of
formation
ΔfG°
kJ · mol−1
Standard
molar entropy
S°
J · K−1 · mol−1
Standard molar
heat capacity at
constant pressure
Cp°
J · K−1 · mol−1
K2O (cr)-361.5[1]-322.1[2]94.1[2]83.7[2]
K2O (g)-63[1]
NO2 (g)33.18[1]51.31[1]240.06[1]37.20[1]
O2 (g)0[1]0[1]205.138[1]29.355[1]
O2 (ao)-11.7[1]16.4[1]110.9[1]
* (cr):Crystalline solid, (g):Gas, (ao):Un-ionized aqueous solution

References

List of references

  1. 1
  2. 2
    James G. Speight (2017)
    Lange's Handbook of Chemistry, 17th edition
    McGraw Hill Education