Magnesium: Properties, Source, Preparation and Uses

Properties of Magnesium

Magnesium has very negative standard reduction potential, that is – 2,37 V. From this value, we can say that this metal is very reactive and easy to oxidize. But in reality, the reactivity of magnesium is less than would be expected.

Why magnesium has less reactivity, while the standard reduction potential of its very negative?

The answer is because a thin coating of magnesium oxide rapidly form over any part of the metal surface when it exposed to the atmosphere. The coating protects the inside part of magnesium metal from the next of oxidizing reaction.

When we heat the metal of magnesium, an intense white flame will produced as a result of the metal oxidized to form magnesium oxide.

2Mg(s) + O2(g) → 2MgO(s)

In its chemistry, magnesium is also differ from the remaining of alkaline earth metal elements.

For example:

When we heating calcium, strontium or barium chloride hydrate causes release of the bound water molecules as steam, leaving the anhydrous metal chloride behind.

SrCl2.2H2O(s)  → SrCl2(s) + 2H2O(g)

∆

But when we heating the hydrate of magnesium chloride (magnesium chloride monohydrate), it decomposes to give magnesium chloride hydroxide and hydrogen chloride gas.

MgCl2.H2O → Mg(OH)Cl(s) + HCl(g)

Same with beryllium, magnesium is also forms compounds that containing covalent bonds. 

For example :

Magnesium metal react with organic compounds called alkyl halides, such as chloroethane, C2H5Cl, in ether as a solvent, to give magnesiumchloroethane (C2H5MgCl).

C2H5Cl(ether) + Mg(s) → C2H5MgCl(ether)

In this substance, magnesium is forming covalent bonds with carbon (in C2H5) and chlorine atoms. This behavior can be explained by the high of charge density that magnesium ion has.

Source of Magnesium

In nature magnesium is found from this two mineral, that is :

• Carnallite with chemical formula MgCl2.KCl.6H2O
• Dolomite with chemical formula MgCO3.CaCO3

 This minerals are an example of mixed – metal salts.

Magnesium is the third most common ion in seawater. So because of that, seawater is a major industrial source to produce the magnesium metal. In facts, 1 km cubic of seawater contains about 1 million tonnes of magnesium ion. So, seawater is serving more than enough magnesium for our needs.

Preparations of Magnesium

The production of magnesium from seawater is used the Dow Chemical extractions process. This process i base on the fact that the magnesium hydroxide has a lower solubility than calcium hydroxide.

So the first step in this process is adding a suspensions of finely powdered calcium hydroxide to the seawater to give solid magnesium hydroxide.

Ca(OH)2(s) + Mg2+(aq) → Ca2+(aq) + Mg(OH)2(s)

The second step is filter the solid of magnesium hydroxide from the mixture. And then, magnesium hydroxide is mixed with hydrochloric acid and the neutralization reaction is happened. This reaction is give a solutions of magnesium chloride.

Mg(OH)2(s) + 2HCl(aq) → MgCl2(aq) + 2H2O(l)

An then, the magnesium chloride solutions is  evaporated to dryness and the recidue is placed in an electrolytic cell similar with the Down cell used for the production of sodium metal.

The electrolysis process will produce magnesium metal on the surface of the cathode compartment as a result of reduction reaction. While, the chlorine ion will oxidize to give chlorine gas in the anode. 

Mg2+ + 2e → Mg(l)

2Cl- → Cl2(g) + 2e

Chlorine gas can reduced back to hydrogen chloride and then used again in the second step to make magnesium chloride.

Uses of Magnesium

• The combustion of magnesium powder metal was used in early photography as a source of illuminations. As we mention before, heating magnesium will gives an intense white light that can use as a source of illuminations.
• Over half of magnesium metal that produced worldwide is used in aluminum – magnesium alloys. This alloys is very useful for many application in our life such as to make the structure of aircraft, railroads, passenger car, rapid transit vehicles and bus bodies. this is because of their low density.

And many other uses of magnesium that you can found by your self. Just search in google, OK!

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