Names | |
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IUPAC name
Sodium carbonate
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Other names
Soda ash, washing soda, soda crystals, sodium trioxocarbonate
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Identifiers | |
3D model (JSmol)
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ChEBI | |
ChEMBL | |
ChemSpider | |
ECHA InfoCard | 100.007.127 |
EC Number |
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E number | E500(i) (acidity regulators, ...) |
PubChem CID
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RTECS number |
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UNII |
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CompTox Dashboard (EPA)
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Properties | |
Na2CO3 | |
Molar mass | 105.9888 g/mol (anhydrous) 286.1416 g/mol (decahydrate) |
Appearance | White solid, hygroscopic |
Odor | Odorless |
Density | |
Melting point | 851 °C (1,564 °F; 1,124 K) (Anhydrous) 100 °C (212 °F; 373 K) decomposes (monohydrate) 33.5 °C (92.3 °F; 306.6 K) decomposes (heptahydrate) 34 °C (93 °F; 307 K) (decahydrate)[2][6] |
Anhydrous, g/100 mL:
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Solubility | Soluble in aq. alkalis,[3] glycerol Slightly soluble in aq. alcohol Insoluble in CS2, acetone, alkyl acetates, alcohol, benzonitrile, liquid ammonia[4] |
Solubility in glycerine | 98.3 g/100 g (155 °C)[4] |
Solubility in ethanediol | 3.46 g/100 g (20 °C)[5] |
Solubility in dimethylformamide | 0.5 g/kg[5] |
Acidity (pKa) | 10.33 |
−4.1·10−5 cm3/mol[2] | |
Refractive index (nD)
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1.485 (anhydrous) 1.420 (monohydrate)[6] 1.405 (decahydrate) |
Viscosity | 3.4 cP (887 °C)[5] |
Structure | |
Monoclinic (γ-form, β-form, δ-form, anhydrous)[7] Orthorhombic (monohydrate, heptahydrate)[1][8] | |
C2/m, No. 12 (γ-form, anhydrous, 170 K) C2/m, No. 12 (β-form, anhydrous, 628 K) P21/n, No. 14 (δ-form, anhydrous, 110 K)[7] Pca21, No. 29 (monohydrate)[1] Pbca, No. 61 (heptahydrate)[8] | |
2/m (γ-form, β-form, δ-form, anhydrous)[7] mm2 (monohydrate)[1] 2/m 2/m 2/m (heptahydrate)[8] | |
a = 8.920(7) Å, b = 5.245(5) Å, c = 6.050(5) Å (γ-form, anhydrous, 295 K)[7] α = 90°, β = 101.35(8)°, γ = 90°
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Octahedral (Na+, anhydrous) | |
Thermochemistry | |
Heat capacity (C)
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112.3 J/mol·K[2] |
Std molar
entropy (S⦵298) |
135 J/mol·K[2] |
Std enthalpy of
formation (ΔfH⦵298) |
−1130.7 kJ/mol[2][5] |
Gibbs free energy (ΔfG⦵)
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−1044.4 kJ/mol[2] |
Hazards | |
Occupational safety and health (OHS/OSH): | |
Main hazards
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Irritant |
GHS labelling: | |
[9] | |
Warning | |
H313+H333, H319[9] | |
P305+P351+P338[9] | |
NFPA 704 (fire diamond) | |
Lethal dose or concentration (LD, LC): | |
LD50 (median dose)
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4090 mg/kg (rat, oral)[10] |
Safety data sheet (SDS) | MSDS |
Related compounds | |
Other anions
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Sodium bicarbonate |
Other cations
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Lithium carbonate Potassium carbonate Rubidium carbonate Cesium carbonate |
Related compounds
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Sodium sesquicarbonate Sodium percarbonate |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Sodium carbonate (also known as washing soda, soda ash and soda crystals) is the inorganic compound with the formula Na2CO3 and its various hydrates. All forms are white, odourless, water-soluble salts that yield alkaline solutions in water. Historically, it was extracted from the ashes of plants grown in sodium-rich soils, and because the ashes of these sodium-rich plants were noticeably different from ashes of wood (once used to produce potash), sodium carbonate became known as "soda ash".[12] It is produced in large quantities from sodium chloride and limestone by the Solvay process, as well as by carbonating sodium hydroxide which is made using the chloralkali process.