Magnesium nitrate

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.

Magnesium nitrate
Names
IUPAC name
Magnesium nitrate
Other names
Nitromagnesite (hexahydrate)
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
ECHA InfoCard 100.030.739
EC Number
  • 233-826-7
RTECS number
  • OM3750000 (anhydrous)
    OM3756000 (hexahydrate)
UNII
UN number 1474
Properties
Mg(NO3)2
Molar mass 148.32 g/mol (anhydrous)
184.35 g/mol (dihydrate)
256.41 g/mol (hexahydr.)
Appearance White 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 ºC)[1]
Solubility moderately soluble in ethanol, ammonia
1.34 (hexahydrate)
Structure
cubic
Thermochemistry
141.9 J/mol K
164 J/mol K
Std enthalpy of
formation (ΔfH⦵298)
 -790.7 kJ/mol
-589.4 kJ/mol
Hazards
Main hazards Irritant
Safety data sheet External MSDS
R-phrases (outdated) R8, R36, R37, R38
S-phrases (outdated) S17, S26, S36
NFPA 704 (fire diamond)
Flash point Non-flammable
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).
N verify (what is YN ?)
Infobox references

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]2+ in the dinitrate salt.[4]

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.

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References
  1. Lide, David R., ed. (2006). CRC Handbook of Chemistry and Physics (87th ed.). Boca Raton, FL: CRC Press. ISBN 0-8493-0487-3.
  2. Thiemann, Michael; Scheibler, Erich and 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.CS1 maint: uses authors parameter (link)
  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.CS1 maint: uses authors parameter (link)


Salts and covalent derivatives of the nitrate ion
HNO3 He
LiNO3 Be(NO3)2 B(NO
3)−
4		 RONO2 NO−
3
NH4NO3		 HOONO2 FNO3 Ne
NaNO3 Mg(NO3)2 Al(NO3)3 Si P S ClONO2 Ar
KNO3 Ca(NO3)2 Sc(NO3)3 Ti(NO3)4 VO(NO3)3 Cr(NO3)3 Mn(NO3)2 Fe(NO3)2
Fe(NO3)3		 Co(NO3)2
Co(NO3)3		 Ni(NO3)2 CuNO3
Cu(NO3)2		 Zn(NO3)2 Ga(NO3)3 Ge As Se Br Kr
RbNO3 Sr(NO3)2 Y(NO3)3 Zr(NO3)4 Nb Mo Tc Ru(NO3)3 Rh(NO3)3 Pd(NO3)2
Pd(NO3)4		 AgNO3
Ag(NO3)2		 Cd(NO3)2 In Sn Sb(NO3)3 Te I Xe(NO3)2
CsNO3 Ba(NO3)2   Hf Ta W Re Os Ir Pt(NO3)2
Pt(NO3)4		 Au(NO3)3 Hg2(NO3)2
Hg(NO3)2		 TlNO3
Tl(NO3)3		 Pb(NO3)2 Bi(NO3)3
BiO(NO3)		 Po(NO3)4 At Rn
FrNO3 Ra(NO3)2   Rf Db Sg Bh Hs Mt Ds Rg Cn Nh Fl Mc Lv Ts Og
↓
La(NO3)3 Ce(NO3)3
Ce(NO3)4		 Pr(NO3)3 Nd(NO3)3 Pm(NO3)3 Sm(NO3)3 Eu(NO3)3 Gd(NO3)3 Tb(NO3)3 Dy(NO3)3 Ho(NO3)3 Er(NO3)3 Tm(NO3)3 Yb(NO3)3 Lu(NO3)3
Ac(NO3)3 Th(NO3)4 PaO2(NO3)3 UO2(NO3)2 Np(NO3)4 Pu(NO3)4 Am(NO3)3 Cm(NO3)3 Bk Cf Es Fm Md No Lr
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