5H2SO4 + 2e− → SO2↑ + 4HSO4− + 2H3O+
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- Reduction of sulfuric acid
- 5H2SO4Sulfuric acid + 2e−ElectronSO2↑Sulfur dioxide + 4HSO4−Hydrogensulfate ion + 2H3O+Hydronium ion⟶
Reduction of sulfuric acid yields sulfur dioxide, hydrogensulfate ion, and hydronium ion (Other reactions are here). This reaction is an oxidation-reduction reaction and is classified as follows:
Table of contents
Reaction data
Chemical equation
- Reduction of sulfuric acid
- 5H2SO4Sulfuric acid + 2e−ElectronSO2↑Sulfur dioxide + 4HSO4−Hydrogensulfate ion + 2H3O+Hydronium ion⟶
General equation
- Reduction of reducible species
- ReactantOxidizing agent + e− ⟶ ProductReduction product
Oxidation state of each atom
- Reduction of sulfuric acid
Reactants
| Chemical formula | Name | Coefficient | Type | Type in general equation |
|---|---|---|---|---|
| H2SO4 | Sulfuric acid | 5 | Oxidizing | – |
| e− | Electron | 2 | – | Electron |
Products
| Chemical formula | Name | Coefficient | Type | Type in general equation |
|---|---|---|---|---|
| SO2 | Sulfur dioxide | 1 | Reduced | – |
| HSO4− | Hydrogensulfate ion | 4 | – | – |
| H3O+ | Hydronium ion | 2 | – | – |
Thermodynamic changes
Changes in standard condition (1)
- Reduction of sulfuric acid◆
ΔrG −75.44 kJ/mol K 1.65 × 1013 pK −13.22
| 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 | 128.50 | −75.44 | 814.7 | 1319 |
per 1 mol of | 25.700 | −15.09 | 162.9 | 263.8 |
per 1 mol of Electron | 64.250 | −37.72 | 407.4 | 659.5 |
per 1 mol of | 128.50 | −75.44 | 814.7 | 1319 |
per 1 mol of Hydrogensulfate ion | 32.125 | −18.86 | 203.7 | 329.8 |
per 1 mol of Hydronium ion | 64.250 | −37.72 | 407.4 | 659.5 |
Changes in standard condition (2)
- Reduction of sulfuric acid◆
ΔrG −75.92 kJ/mol K 2.00 × 1013 pK −13.30
| 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 | 102.35 | −75.92 | 728.4 | – |
per 1 mol of | 20.470 | −15.18 | 145.7 | – |
per 1 mol of Electron | 51.175 | −37.96 | 364.2 | – |
per 1 mol of | 102.35 | −75.92 | 728.4 | – |
per 1 mol of Hydrogensulfate ion | 25.587 | −18.98 | 182.1 | – |
per 1 mol of Hydronium ion | 51.175 | −37.96 | 364.2 | – |
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 |
|---|---|---|---|---|
| H2SO4 (cr) | – | – | – | – |
| H2SO4 (l) | -813.989[1] | -690.003[1] | 156.904[1] | 138.91[1] |
| H2SO4 (ai) | -909.27[1] | -744.53[1] | 20.1[1] | -293[1] |
| H2SO4 (l) 1 hydrate | -1127.621[1] | -950.383[1] | 211.54[1] | 214.85[1] |
| H2SO4 (l) 2 hydrate | -1427.100[1] | -1199.650[1] | 276.40[1] | 260.83[1] |
| H2SO4 (l) 3 hydrate | -1720.402[1] | -1443.980[1] | 345.39[1] | 318.95[1] |
| H2SO4 (l) 4 hydrate | -2011.199[1] | -1685.863[1] | 414.59[1] | 382.21[1] |
| H2SO4 (l) 6.5 hydrate | -2733.256[1] | -2285.734[1] | 587.89[1] | 570.28[1] |
| e− | – | – | – | – |
* (cr):Crystalline solid, (l):Liquid, (ai):Ionized 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 |
|---|---|---|---|---|
| SO2 (l) | -320.5[1] | – | – | – |
| SO2 (g) | -296.830[1] | -300.194[1] | 248.22[1] | 39.87[1] |
| SO2 (ao) | -322.980[1] | -300.676[1] | 161.9[1] | – |
| HSO4− (ao) | -887.34[1] | -755.91[1] | 131.8[1] | -84[1] |
| H3O+ (ao) | -285.830[1] | -237.129[1] | 69.91[1] | 75.291[1] |
* (l):Liquid, (g):Gas, (ao):Un-ionized aqueous solution
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°, -813.989 kJ · mol−1
- ^ ΔfG°, -690.003 kJ · mol−1
- ^ S°, 156.904 J · K−1 · mol−1
- ^ Cp°, 138.91 J · K−1 · mol−1
- ^ ΔfH°, -909.27 kJ · mol−1
- ^ ΔfG°, -744.53 kJ · mol−1
- ^ S°, 20.1 J · K−1 · mol−1
- ^ Cp°, -293. J · K−1 · mol−1
- ^ ΔfH°, -1127.621 kJ · mol−1
- ^ ΔfG°, -950.383 kJ · mol−1
- ^ S°, 211.54 J · K−1 · mol−1
- ^ Cp°, 214.85 J · K−1 · mol−1
- ^ ΔfH°, -1427.100 kJ · mol−1
- ^ ΔfG°, -1199.650 kJ · mol−1
- ^ S°, 276.40 J · K−1 · mol−1
- ^ Cp°, 260.83 J · K−1 · mol−1
- ^ ΔfH°, -1720.402 kJ · mol−1
- ^ ΔfG°, -1443.980 kJ · mol−1
- ^ S°, 345.39 J · K−1 · mol−1
- ^ Cp°, 318.95 J · K−1 · mol−1
- ^ ΔfH°, -2011.199 kJ · mol−1
- ^ ΔfG°, -1685.863 kJ · mol−1
- ^ S°, 414.59 J · K−1 · mol−1
- ^ Cp°, 382.21 J · K−1 · mol−1
- ^ ΔfH°, -2733.256 kJ · mol−1
- ^ ΔfG°, -2285.734 kJ · mol−1
- ^ S°, 587.89 J · K−1 · mol−1
- ^ Cp°, 570.28 J · K−1 · mol−1
- ^ ΔfH°, -320.5 kJ · mol−1
- ^ ΔfH°, -296.830 kJ · mol−1
- ^ ΔfG°, -300.194 kJ · mol−1
- ^ S°, 248.22 J · K−1 · mol−1
- ^ Cp°, 39.87 J · K−1 · mol−1
- ^ ΔfH°, -322.980 kJ · mol−1
- ^ ΔfG°, -300.676 kJ · mol−1
- ^ S°, 161.9 J · K−1 · mol−1
- ^ ΔfH°, -887.34 kJ · mol−1
- ^ ΔfG°, -755.91 kJ · mol−1
- ^ S°, 131.8 J · K−1 · mol−1
- ^ Cp°, -84. 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