>> Study Material
>> IIT JEE Chemistry
>> Inorganic Chemistry
>> S and P-Block Elements
>> Properties of Magnesium
Properties of Magnesium
(i) Magnesium is a silvery white metal which soon becomes dull in air.
(ii) It is a light metal with a density of 1.74 g cm-3.
(iii)It is fairly malleable and ductile.
(i) Action of oxygen or air
Magnesium does not react with dry air but slowly gets tarnished in most air due to the formation of a thin film of the oxide, MgO. It burns in oxygen or air with a dazzling light.
2Mg + O2 ——→ 2MgO
(ii) Action of CO2 and SO2
Because of its great affinity for oxygen magnesium keeps on burning even in CO2 or SO2.
2Mg + CO2 ——→ 2MgO + C
2Mg + SO2 ——→ 2MgO + S
On heating magnesium combines with nitrogen to form magnesium nitride.
3Mg + N2 ——→ Mg3N2
Thus when magnesium burns in air both the oxide and the nitride are formed.
(iv) Action of halogens
Magnesium on heating with halogens readily forms the halides e.g.
Mg + CI2 ——→ MgCI2
Magnesium does not decompose water in cold but decomposes boiling water or steam.
Mg + H2O ( steam) ——→ MgO + H2
(vi) Action of Acids
Dilute acids reacts with magnesium to produce dihydrogen.
Mg + 2HCI ——→ MgCi2 + H2
Mg + H2SO4 ——→ MgSO4 + H2
Mg + 2HNO3 ——→ Mg ( NO3)2 + H2
However with conc. H2SO4, SO2 is produced
Mg + 2H2SO4 ——→ MgSo4 + SO2 + 2H2O
(vii) Reaction with alkyl halide
Magnesium reacts with alkyl halides in dry ether to form covalent compound called Grignard reagent.
Mg + C2H5I ——→C2H5MgI
Uses of Magnesium
(i) The chief use of magnesium is in the preparation of alloys with aluminum, zinc, manganese and tin.
Duralium (Al = 95%, Cu = 4%. Mn = 0.5%, Mg = 0.5%)
Mangnalium (Al = 90% & Mg = 10%)
Duralium being light, tough and durable is used for the manufacture of airplanes and automobiles parts. Magnalium being light, tough and hard is used for making balance beams.
(ii) Magnesium burns with an intense lights, therefore, Mg (as power or ribbon) is used in flash bulbs for photography, fireworks and signals fibres.
(iii) Mg is used for ignition of thermite charge in aluminothermy.
(iv) A suspension of magnesium hydroxide known as milk of magnesium is used as an antacid for patients suffering from acidity.
(v) In preparation of Grignard reagent.
(vi)Being a reducing agent, magnesium is used in the extraction of boron and silicon from their respective oxides.
B2O3 + 3Mg ——→ 3 MgO + 2B
SiO2 + 2Mg ——→ 2MgO + Si
The chemistry of Lithium is very much similar to that of magnesium even though they are placed in different groups - Explain.
The ratio of their charge to size is nearly same by which they show the diagonal relationship.
Name some minerals of magnesium.
Minerals of magnesium are:
(iii) Epsom salt
Write the chemical formulae of the following ores:
(i) Dolomite (ii) Epsom salt
(iii) Carnallite (iv) Magnesite
(i) Dolomite – MgCO3.CaCO3
(ii) Epsom salt – MgSO4.7H2O
(iii) Carnallite – KCl.MgCl2.6H2O
What is milk of magnesia? Give its one use.
What happens when magnesium reacts with (i) CO2 (ii) SO2 gas?