Preparation & Properties of Compounds

Introduction :
This chapter focuses on the various aspects of compounds of aluminum, iron, tin, silver and other important metals along with the various reactions, the metals and their compounds undergo. It also deals with the preparation, properties of non metals like carbon, nitrogen, phosphorous, their various fertilizers widely used in the industry.

Compounds of Aluminium :

Aluminium oxide or Alumina (Al2O3)
(a) α – Al2O3 (rhombic lattice) is dense, hard and resistant to chemical attack.

α – Al2O3 occurs in the earth’s crust as corundum, (Al2O3). Transparent coloured crystals of corundum, viz. Ruby (red due to the presence of Cr) and sapphire (blue due to Ti and Re) are used as precious stones (gems)

(b) γ – Al2O3 is less dense, soft and has a high surface area. It is used as an excellent selective adsorbent in dehydration, decolourisation and chromatography.

Aluminium chloride: (AlCl3) :

(a) Anhydrous Aluminium chloride (AlCl3) on heating it sublimes at 180°C and the vapour density corresponds to the formula Al2Cl6

The dimeric formula is retained in non polar solvents but it broken into [Al(H2O)6]Cl3 on dissolution in water on account of high heat of hydration

Aluminium :

Aluminium ions crystallize from aqueous solutions, forming double salts. These are called aluminium alums and have the general formula
[M'(H2O)6][Al(H2O)6](SO4)2 , M’ is a singly charged cation such as Na+ , K+ or NH4+

Some M3+ ions other than Al3+ also form alums of formula [M'(H2O)6[ [MIII(H2O)6](SO4)2 Some of important alums are

Potash alum : K2SO4. Al2(SO4)3.24H2O

Ammonium alum : (NH4)2SO4. Al2(SO4)3.24H2O

Sodium alum : Na2SO4.Al2(SO4)3.24H2O

Chrome alum : K2SO4.Cr2(SO4)3.24H2O

Ferric alum : (NH4)2SO4.Fe2(SO4)3.24H2O

Also Read :

Compounds of Boron
Compounds of Silicon
Compounds of Nitrogen
Sulphur Chemistry

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