Magnesium nitrate

Last updated
Magnesium nitrate
Magnesium nitrate Magnesium nitrate.png
Magnesium nitrate
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Names
IUPAC name
Magnesium nitrate
Other names
Nitromagnesite (hexahydrate)
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
ECHA InfoCard 100.030.739 OOjs UI icon edit-ltr-progressive.svg
EC Number
  • 233-826-7
PubChem CID
RTECS number
  • OM3750000 (anhydrous)
    OM3756000 (hexahydrate)
UNII
UN number 1474
  • InChI=1S/Mg.2NO3/c;2*2-1(3)4/q+2;2*-1 X mark.svgN
    Key: YIXJRHPUWRPCBB-UHFFFAOYSA-N X mark.svgN
  • InChI=1/Mg.2NO3/c;2*2-1(3)4/q+2;2*-1
    Key: YIXJRHPUWRPCBB-UHFFFAOYAA
  • [N+](=O)([O-])[O-].[N+](=O)([O-])[O-].[Mg+2]
Properties
Mg(NO3)2
Molar mass 148.32 g/mol (anhydrous)
184.35 g/mol (dihydrate)
256.41 g/mol (hexahydr.)
AppearanceWhite crystalline solid
Density 2.3 g/cm3 (anhydrous)
2.0256 g/cm3 (dihydrate)
1.464 g/cm3 (hexahydrate)
Melting point 129 °C (264 °F; 402 K) (dihydrate)
88.9 °C (hexahydrate)
Boiling point 330 °C (626 °F; 603 K) decomposes
71 g/100 mL (25 °C) [1]
Solubility moderately soluble in ethanol, ammonia
1.34 (hexahydrate)
Structure
cubic
Thermochemistry
141.9 J/mol K
Std molar
entropy (S⦵298)
164 J/mol K
−790.7 kJ/mol
−589.4 kJ/mol
Hazards
Occupational safety and health (OHS/OSH):
Main hazards
Irritant
GHS labelling:
GHS-pictogram-rondflam.svg GHS-pictogram-exclam.svg
Warning
H272, H315, H319, H335
P210, P220, P221, P261, P264, P271, P280, P302+P352, P304+P340, P305+P351+P338, P312, P321, P332+P313, P337+P313, P362, P370+P378, P403+P233, P405, P501
NFPA 704 (fire diamond)
NFPA 704.svgHealth 1: Exposure would cause irritation but only minor residual injury. E.g. turpentineFlammability 0: Will not burn. E.g. waterInstability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazard OX: Oxidizer. E.g. potassium perchlorate
1
0
0
OX
Safety data sheet (SDS) External MSDS
Related compounds
Other anions
Magnesium sulfate
Magnesium chloride
Other cations
Beryllium nitrate
Calcium nitrate
Strontium nitrate
Barium nitrate
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Magnesium nitrate refers to inorganic compounds with the formula Mg(NO3)2(H2O)x, where x = 6, 2, and 0. All are white solids. [2] The anhydrous material is hygroscopic, quickly forming the hexahydrate upon standing in air. All of the salts are very soluble in both water and ethanol.

Contents

Occurrence, preparation, structure

Being highly water-soluble, magnesium nitrate occurs naturally only in mines and caverns as nitromagnesite (hexahydrate form). [3]

The magnesium nitrate used in commerce is made by the reaction of nitric acid and various magnesium salts.

Structure of [Mg(H2O)6] in the dinitrate salt. 80445-ICSD.png
Structure of [Mg(H2O)6] in the dinitrate salt.

Use

The principal use is as a dehydrating agent in the preparation of concentrated nitric acid. [2]

Its fertilizer grade has 10.5% nitrogen and 9.4% magnesium, so it is listed as 10.5-0-0 + 9.4% Mg. Fertilizer blends containing magnesium nitrate also have ammonium nitrate, calcium nitrate, potassium nitrate and micronutrients in most cases; these blends are used in the greenhouse and hydroponics trade.

Reactions

Magnesium nitrate reacts with alkali metal hydroxide to form the corresponding nitrate:

Mg(NO3)2 + 2 NaOH → Mg(OH)2 + 2 NaNO3.

Since magnesium nitrate has a high affinity for water, heating the hexahydrate does not result in the dehydration of the salt, but rather its decomposition into magnesium oxide, oxygen, and nitrogen oxides:

2 Mg(NO3)2 → 2 MgO + 4 NO2 + O2.

The absorption of these nitrogen oxides in water is one possible route to synthesize nitric acid. Although inefficient, this method does not require the use of any strong acid.

It is also occasionally used as a desiccant.

References

  1. ↑ Lide, David R., ed. (2006). CRC Handbook of Chemistry and Physics (87th ed.). Boca Raton, Florida: CRC Press. ISBN   0-8493-0487-3.
  2. 1 2 Thiemann, Michael; Scheibler, Erich; Wiegand, Karl Wilhelm (2005). "Nitric Acid, Nitrous Acid, and Nitrogen Oxides". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a17_293. ISBN   3-527-30673-0.
  3. ↑ Mindat, http://www.mindat.org/min-2920.html
  4. ↑ Schefer, J.; Grube, M. (1995). "Low temperature structure of magnesium nitrate hexahydrate, Mg (N O3)2 . 6(H2 O): a neutron diffraction study at 173 K". Materials Research Bulletin. 30: 1235–1241. doi:10.1016/0025-5408(95)00122-0.
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