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Chemistry Project Report on “Preparation of Potash Alum from Scrap Aluminium”
Declaration I, ____________ student of ___________________ is doing project report entitled “Preparation of Potash Alum from Scrap Aluminium” being submitted to ___________________is an original piece of work done by me. (Signature)
Introduction to the Topic “Preparation of Potash Alum from Scrap Aluminium”Aluminium is used for the manufacture of aeroplanes, automobiles, lawn furniture as well as for aluminium cans because of its low density, high tensile strength and resistance and resistance to corrosion. Being a good conductor of electricity it is used for transmission of electricity also. It is also used for making utensils. The recycling of aluminium cans and other aluminium products is a very positive contribution to saving our natural resources. Most of the recycled aluminium is melted and recast into other aluminium metal products or used in the production of various aluminium compounds, the most common of which are the alums. Alums are double sulphates having general formula X2SO4.M2(SO4)3.24H2O - X = Monovalent cation; M = Trivalent cation Some important alum and their names are given below: K2SO4.Al2(SO4)3.24H2O - Potash Alum Preparation of Potash Alum : Na2SO4.Al2(SO4)3.24H2O - Soda Alum K2SO4.Cr2(SO4)3.24H2O - Chrome Alum (NH)2SO4.Fe2(SO4)3.24H2O - Ferric Alum Potash alum is used in fire extinguishers, food stuffs, papermaking and in purification of water. Soda alum used in baking powders and chrome alum is used in tanning leather and water proofing fabrics.
In addition to these primary uses, alum is also used as : (i) An astringent a substance or preparation that draws together or constricts body tissues and is effective in stopping the flow of blood or other secretions. Alum has also been used by conventional hairdressers for treating shaving cuts. (ii) A mordant substances used in dyeing to fix certain dyes on cloth. Either the mordant (if it is colloidal) or a colloid produced by the mordant adheres to the fiber, attracting and fixing the colloidal mordant dye. The insoluble, colored precipitate that is formed is called a lake. Alum is a basic mordant used for fixing acid dyes. (iii) For the removal of phosphate from natural and waste waters the aluminium ions of alum combine with the orthophosphate around pH 6 to form the solid aluminum hydroxy phosphate which is precipitated and ; (iv) For fireproofing fabrics The major uses of alums are based on two important properties, namely precipitation of Al(OH)3 and those related to the acidity created by the production of hydrogen ions. Al(H2O)6+3 → Al(OH)3 ↓ + 3H2O + 3H+ The H+ ions generated are used foe reacting with sodium bicarbonate to release CO2. This property is made use of in baking powder and CO2 fire extinguishers.
Requirements for Experiment :
TheoryAluminium metal is treated with hot aqueous KOH solution. Aluminium dissolves as potassium aluminate, KAl(OH)4, salt. 2Al(s) + 2KOH(aq) + 6H2O(l) → 2KAl(OH)4 (aq) + 3H2 Potassium aluminate solution on treatment with dil. Sulphuric acid first gives precipitate Al(OH)3, which dissolves on addition of small excess of H2SO4 and heating. 2KOH(aq) + H2SO4(aq) → 2Al(OH)3 (s) + K2SO4(aq) + 2H2O(l) 2Al(OH)3 (s) + 3 H2SO4(aq) → Al2(SO4)3(aq) + 6H2O(l) The resulting solution is concentrated to near saturation and cooled. On cooling crystals of potash alum crystallize out. K2SO4(aq) + Al2(SO4)3(aq) + 24H2O(l) → K2SO4.Al2(SO4)3. 24H2O(s)
Reactions2Al(s) + 2KOH(aq) + 6H2O(l) → 2KAl(OH)4 (aq) + 3H2 K2SO4(aq) + Al2(SO4)3(aq) + 24H2O(l) → K2SO4.Al2(SO4)3. 24H2O(s) 2Al(OH)3 (s) + 3 H2SO4(aq) → Al2(SO4)3(aq) + 6H2O(l) 2KOH(aq) + H2SO4(aq) → 2Al(OH)3 (s) + K2SO4(aq) + 2H2O(l) K2SO4(aq) + Al2(SO4)3(aq) + 24H2O(l) → K2SO4.Al2(SO4)3. 24H2O(s)
Procedure
Observations
ResultFrom the above study and theory we can say that potash alum was prepared from aluminium scrap.
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