Sodium chromate
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| Names | |
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| IUPAC name
Sodium chromate
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| Other names
Chromic acid, (Na2CrO4), disodium salt
Chromium disodium oxide Rachromate |
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| Identifiers | |
7775-11-3  |
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| ChEBI | CHEBI:78671  |
| EC Number | 231-889-5 |
| Jmol 3D model | Interactive image |
| PubChem | 24488 |
| RTECS number | GB2955000 |
| UN number | 3288 |
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| Properties | |
| Na2CrO4 | |
| Molar mass | 161.97 g/mol |
| Appearance | yellow crystals |
| Odor | odorless |
| Density | 2.698 g/cm3 |
| Melting point | 792 °C (1,458 °F; 1,065 K) (anhydrous) 20 °C (decahydrate) |
| 31.8 g/100 mL (0 °C) 84.5 g/100 mL (25 °C) 126.7 g/100 mL (100 °C) |
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| Solubility | slightly soluble in ethanol |
| Solubility in methanol | 0.344 g/100 mL (25 °C) |
| Structure | |
| orthorhombic (hexagonal above 413 °C) | |
| Thermochemistry | |
| 142.1 J/mol K | |
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Std molar
entropy (S |
174.5 J/mol K |
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Std enthalpy of
formation (ΔfH |
−1329 kJ/mol |
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Gibbs free energy (ΔfG˚)
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-1232 kJ/mol |
| Vapor pressure | {{{value}}} |
| Related compounds | |
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Other anions
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Sodium dichromate Sodium molybdate Sodium tungstate |
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Other cations
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Potassium chromate Calcium chromate Barium chromate |
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Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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 verify (what is ?) |
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| Infobox references | |
Sodium chromate is the inorganic compound with the formula Na2CrO4. It exists as a yellow hygroscopic solid, which can form tetra-, hexa-, and decahydrates. It is an intermediate in the extraction of chromium from its ores. Sodium chromate, like other hexavalent chromium compounds, is toxic and carcinogenic.[1]
Contents
Production and reactivity
It is obtained on a vast scale by roasting chromium ores in air in the presence of sodium carbonate:
- Cr2O3 + 2 Na2CO3 + 3/2 O2 → 2 Na2CrO4 + 2 CO2
This process converts the chromium into a water-extractable form, leaving behind iron oxides. Subsequent to its formation, the chromate salt is converted to sodium dichromate, the precursor to most chromium compounds and materials.[1] The industrial route to chromium(III) oxide involves reduction of sodium chromate with sulfur.
Acid-base behavior
It converts to sodium dichromate when treated with acids:
- 2 Na2CrO4 + 2 H+ → + H2O + Na2Cr2O7
Further acidification affords chromium trioxide:
- Na2CrO4 + H2SO4 → CrO3 + Na2SO4 + H2O
Uses
Aside from its central role in the production of chromium from its ores, sodium chromate is used as a corrosion inhibitor in the petroleum industry.[1] It is also a dyeing auxiliary in the textile industry[1] and a wood preservative.[2] It is a diagnostic pharmaceutical in determining red blood cell volume.[3]
In organic chemistry, sodium chromate is used as an oxidant, converting primary alcohols to carboxylic acids and secondary alcohols to ketones.[4]
See also
References
- ↑ 1.0 1.1 1.2 1.3 Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Lua error in package.lua at line 80: module 'strict' not found.
- ↑ Louis F. Fieser "Δ4-cholesten-3,6-dione" Org. Synth. 1955, 35, 36. doi:10.15227/orgsyn.035.0036
Further reading
- Lua error in package.lua at line 80: module 'strict' not found.
- Record of Sodium chromate in the GESTIS Substance Database of the IFA
