5H3AsO3 🔥→ 3H3AsO4 + 2As + 3H2O
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- Decomposition of arsenous acid
Decomposition of arsenous acid yields arsenic acid, , and water (Other reactions are here). This reaction is an oxidation-reduction reaction and is classified as follows:
Table of contents
Reaction data
Chemical equation
- Decomposition of arsenous acid
General equation
- Thermal decomposition with redox
- Thermally decomposable substanceSelf redox agent🔥⟶ ProductOxidation product + ProductReduction product
Oxidation state of each atom
- Decomposition of arsenous acid
Reactants
| Chemical formula | Name | Coefficient | Type | Type in general equation |
|---|---|---|---|---|
| H3AsO3 | Arsenous acid | 5 | – | Thermally decomposable |
Products
| Chemical formula | Name | Coefficient | Type | Type in general equation |
|---|---|---|---|---|
| H3AsO4 | Arsenic acid | 3 | Oxidized | – |
| 2 | Reduced | – | ||
| H2O | Water | 3 | – | – |
Thermodynamic changes
Changes in standard condition (1)
- Decomposition of arsenous acid◆
ΔrG 189.6 kJ/mol K 0.61 × 10−33 pK 33.22
| 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 | 146.0 | 189.6 | −143 | – |
per 1 mol of | 29.20 | 37.92 | −28.6 | – |
per 1 mol of | 48.67 | 63.20 | −47.7 | – |
| 73.00 | 94.80 | −71.5 | – | |
per 1 mol of | 48.67 | 63.20 | −47.7 | – |
Changes in standard condition (2)
- Decomposition of arsenous acid
| 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 | 139.7 | – | – | – |
per 1 mol of | 27.94 | – | – | – |
per 1 mol of | 46.57 | – | – | – |
| 69.85 | – | – | – | |
per 1 mol of | 46.57 | – | – | – |
Changes in standard condition (3)
- Decomposition of arsenous acid
| 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 | 146.0 | – | – | – |
per 1 mol of | 29.20 | – | – | – |
per 1 mol of | 48.67 | – | – | – |
| 73.00 | – | – | – | |
per 1 mol of | 48.67 | – | – | – |
Changes in standard condition (4)
- Decomposition of arsenous acid
| 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 | 139.7 | – | – | – |
per 1 mol of | 27.94 | – | – | – |
per 1 mol of | 46.57 | – | – | – |
| 69.85 | – | – | – | |
per 1 mol of | 46.57 | – | – | – |
Thermodynamic data of reactants
| Chemical formula | Standard 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 |
|---|---|---|---|---|
| H3AsO3 (ao) | -742.2[1] | -639.80[1] | 195.0[1] | – |
| H3AsO3 (aq) | -742.2[1] | – | – | – |
* (ao):Un-ionized aqueous solution, (aq):Aqueous solution
Thermodynamic data of products
| Chemical formula | Standard 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 |
|---|---|---|---|---|
| H3AsO4 (cr) | -906.3[1] | – | – | – |
| H3AsO4 (ao) | -902.5[1] | -766.0[1] | 184[1] | – |
| H3AsO4 (aq) | -904.6[1] | – | – | – |
| (cr) α, gray, metallic | 0[1] | 0[1] | 35.1[1] | 24.64[1] |
| (cr) γ, yellow, cubic | 14.6[1] | – | – | – |
| (am) β | 4.2[1] | – | – | – |
| (g) | 302.5[1] | 261.0[1] | 174.21[1] | 20.786[1] |
| H2O (cr) | – | – | – | – |
| H2O (l) | -285.830[1] | -237.129[1] | 69.91[1] | 75.291[1] |
| H2O (g) | -241.818[1] | -228.572[1] | 188.825[1] | 33.577[1] |
* (cr):Crystalline solid, (ao):Un-ionized aqueous solution, (aq):Aqueous solution, (am):Amorphous solid, (g):Gas, (l):Liquid
References
List of references
- 1Janiel J. Reed (1989)The NBS Tables of Chemical Thermodynamic Properties: Selected Values for Inorganic and C1 and C2 Organic Substances in SI UnitsNational Institute of Standards and Technology (NIST)
- ^ ΔfH°, -742.2 kJ · mol−1
- ^ ΔfG°, -639.80 kJ · mol−1
- ^ S°, 195.0 J · K−1 · mol−1
- ^ ΔfH°, -742.2 kJ · mol−1
- ^ ΔfH°, -906.3 kJ · mol−1
- ^ ΔfH°, -902.5 kJ · mol−1
- ^ ΔfG°, -766.0 kJ · mol−1
- ^ S°, 184. J · K−1 · mol−1
- ^ ΔfH°, -904.6 kJ · mol−1
- ^ ΔfH°, 0 kJ · mol−1
- ^ ΔfG°, 0 kJ · mol−1
- ^ S°, 35.1 J · K−1 · mol−1
- ^ Cp°, 24.64 J · K−1 · mol−1
- ^ ΔfH°, 14.6 kJ · mol−1
- ^ ΔfH°, 4.2 kJ · mol−1
- ^ ΔfH°, 302.5 kJ · mol−1
- ^ ΔfG°, 261.0 kJ · mol−1
- ^ S°, 174.21 J · K−1 · mol−1
- ^ Cp°, 20.786 J · K−1 · mol−1
- ^ ΔfH°, -285.830 kJ · mol−1
- ^ ΔfG°, -237.129 kJ · mol−1
- ^ S°, 69.91 J · K−1 · mol−1
- ^ Cp°, 75.291 J · K−1 · mol−1
- ^ ΔfH°, -241.818 kJ · mol−1
- ^ ΔfG°, -228.572 kJ · mol−1
- ^ S°, 188.825 J · K−1 · mol−1
- ^ Cp°, 33.577 J · K−1 · mol−1