Magnesium hydroxide

Magnesium hydroxide
Magnesium hydroxide
Are common
Systematic ; name	Magnesium hydroxide
Chem. formula	Mg (OH) 2
Rat formula	Mg (OH) 2
Physical properties
condition	solid
Molar mass	58.35 g / mol
Density	2,3446 (20 ° C)
Thermal properties
T. melt.	350 ° C
T. aux.	non-flammable ° C
Enthalpy of Education	–925 kJ / mol
Chemical properties
Solubility in water	0.0012 g / 100 ml
Optical properties
Refractive index	1.559
Structure
Crystal structure	trigonal
Classification
Reg. CAS number	1309-42-8
PubChem
Reg. EINECS number
Smiles
Inchi
Codex Alimentarius
RTECS	OM3570000
Chebi
ChemSpider
Security
Toxicity	0 one one

Magnesium hydroxide - an inorganic substance , the basic hydroxide of a magnesium metal, has the formula ${{\ce {Mg(OH)2}}}$ ${\ displaystyle {{\ ce {Mg (OH) 2}}}}$ ${\ displaystyle {\ ce {Mg (OH) 2}}}$ . Weak, slightly soluble base.

Description

Under standard conditions , magnesium hydroxide is an amorphous substance. At temperatures above 350 ° C, it decomposes into magnesium oxide and water . It absorbs carbon dioxide and water from the air to form basic magnesium carbonate. Magnesium hydroxide is practically insoluble in water , but soluble in ammonium salts. It is a weak base , even an insignificant part of it, dissolved in water, gives the solution a slightly alkaline reaction and colors indicators, for example, phenolphthalein, in pink. It is found in nature in the form of the brucite mineral. ^[2]

Getting

The interaction of soluble magnesium salts with alkalis :

In general form:

${\mathsf {Mg^{2+}+2\ OH^{-}\longrightarrow Mg(OH)_{2}\downarrow }}$ ${\ displaystyle {\ mathsf {Mg ^ {2 +} + 2 \ OH ^ {-} \ longrightarrow Mg (OH) _ {2} \ downarrow}}}$ ${\mathsf {Mg^{2+}+2\ OH^{-}\longrightarrow Mg(OH)_{2}\downarrow }}$

Examples:

${\mathsf {MgCl_{2}+2NaOH\longrightarrow Mg(OH)_{2}\downarrow +2NaCl}}$ ${\ displaystyle {\ mathsf {MgCl_ {2} + 2NaOH \ longrightarrow Mg (OH) _ {2} \ downarrow + 2NaCl}}}$ ${\mathsf {MgCl_{2}+2NaOH\longrightarrow Mg(OH)_{2}\downarrow +2NaCl}}$

${\mathsf {Mg(NO_{3})_{2}+2KOH\longrightarrow Mg(OH)_{2}\downarrow +2KNO_{3}}}$ ${\ displaystyle {\ mathsf {Mg (NO_ {3}) _ {2} + 2KOH \ longrightarrow Mg (OH) _ {2} \ downarrow + 2KNO_ {3}}}}$

The interaction of a solution of magnesium chloride with calcined dolomite :

${\mathsf {MgCl_{2}+CaO\cdot MgO+2H_{2}O\longrightarrow 2Mg(OH)_{2}\downarrow +CaCl_{2}}}$ ${\ displaystyle {\ mathsf {MgCl_ {2} + CaO \ cdot MgO + 2H_ {2} O \ longrightarrow 2Mg (OH) _ {2} \ downarrow + CaCl_ {2}}}}$

The interaction of metallic magnesium with water vapor :

${\mathsf {Mg+2H_{2}O\longrightarrow Mg(OH)_{2}\downarrow +H_{2}\uparrow }}$ ${\ displaystyle {\ mathsf {Mg + 2H_ {2} O \ longrightarrow Mg (OH) _ {2} \ downarrow + H_ {2} \ uparrow}}}$

Chemical Properties

Like all weak bases, magnesium hydroxide is thermally unstable. Decomposes on heating to 350 ° C:

${\mathsf {Mg(OH)_{2}{\xrightarrow {\Delta T}}MgO+H_{2}O}}$ ${\ displaystyle {\ mathsf {Mg (OH) _ {2} {\ xrightarrow {\ Delta T}} MgO + H_ {2} O}}}$

It interacts with acids to form salt and water ( neutralization reaction ) :

${\mathsf {Mg(OH)_{2}+2HCl\longrightarrow MgCl_{2}+2H_{2}O}}$ ${\ displaystyle {\ mathsf {Mg (OH) _ {2} + 2HCl \ longrightarrow MgCl_ {2} + 2H_ {2} O}}}$

${\mathsf {Mg(OH)_{2}+H_{2}SO_{4}\longrightarrow MgSO_{4}+2H_{2}O}}$ ${\ displaystyle {\ mathsf {Mg (OH) _ {2} + H_ {2} SO_ {4} \ longrightarrow MgSO_ {4} + 2H_ {2} O}}}$

Reaction with acid oxides to form salt and water :

${\mathsf {Mg(OH)_{2}+SO_{3}\longrightarrow MgSO_{4}+H_{2}O}}$ ${\ displaystyle {\ mathsf {Mg (OH) _ {2} + SO_ {3} \ longrightarrow MgSO_ {4} + H_ {2} O}}}$

Interaction with hot concentrated solutions of alkalis with the formation of hydroxomagnesates :

${\mathsf {Mg(OH)_{2}+2NaOH\longrightarrow Na_{2}[Mg(OH)_{4}]}}$ ${\ displaystyle {\ mathsf {Mg (OH) _ {2} + 2NaOH \ longrightarrow Na_ {2} [Mg (OH) _ {4}]}}}$

${\mathsf {Mg(OH)_{2}+Sr(OH)_{2}\longrightarrow Sr[Mg(OH)_{4}]}}$ ${\ displaystyle {\ mathsf {Mg (OH) _ {2} + Sr (OH) _ {2} \ longrightarrow Sr [Mg (OH) _ {4}]}}}$

Application

Magnesium hydroxide is used to bind sulfur dioxide , as a flocculant for wastewater treatment, as a fire retardant in thermoplastic polymers ( polyolefins , PVC ), as an additive in detergents, to produce magnesium oxide , sugar refining, as a component of toothpastes.

In medicine, it is used as a medicine to neutralize acid in the stomach , and also as a very strong laxative .

In the European Union , magnesium hydroxide is registered as a food supplement E528.

Notes

Literature

Chemical Encyclopedia / Editorial Board: Knunyants I.L. et al. - M .: Soviet Encyclopedia, 1990. - T. 2 (Daf-Med). - 671 p. - ISBN 5-82270-035-5 .

[1] Magnesium Hydroxide at XuMuK.Ru

[2] Description of magnesium hydroxide on XuMuK.Ru

Magnesium hydroxide

Are common
Systematic name	Magnesium hydroxide
Chem. formula	Mg (OH) ₂
Rat formula	Mg (OH) ₂
Physical properties
condition	solid
Molar mass	58.35 g / mol
Density	2,3446 (20 ° C) ^[1]
Thermal properties
T. melt.	350 ° C
T. aux.	non-flammable ° C
Enthalpy of Education	–925 kJ / mol
Chemical properties
Solubility in water	0.0012 g / 100 ml
Optical properties
Refractive index	1.559
Structure
Crystal structure	trigonal
Classification
Reg. CAS number	1309-42-8
PubChem
Reg. EINECS number
Smiles
Inchi
Codex Alimentarius
RTECS	OM3570000
Chebi
ChemSpider
Security
Toxicity	0 one one