Is the chemical formula for Aluminum Sulfate Al2(SO4)3?How and why is Al2(SO4)3 wrong?
Aluminium sulfate or Aluminium Sulphate, written as Al2(SO4)3 or Al2O12S3 Aluminium sulfate is an industrial chemical used as a flocculating agent in the purification of drinking water and waste water treatment plants, and also in paper manufacturing. Aluminium sulfate is sometimes incorrectly referred to as alum but alums are closely related compounds typified by KAl(SO4)2.12H2O. The anhydrous form occurs naturally as a rare mineral millosevichite, found e.g. in volcanic environments and on burning coal-mining waste dumps. Aluminium sulfate is rarely, if ever, encountered as the anhydrous salt. It forms a number of different hydrates, of which the hexadecahydrate Al2(SO4)3?16H2O and octadecahydrate Al2(SO4)3?18H2O are the most common. The heptadecahydrate, whose formula can be written as [Al(H2O)6]2(SO4)3?5H2O, occurs naturally as the mineral alunogen. 
Al2(SO4)3 is right. Because SO4 is 2- And Al is 3+ So the 3 transfers to the end next to SO4 And the 2 of SO4 2- goes next to the Al So Al2(SO4)3 is right. It can also be found as an hydrate which you can read in the copy paste story of a person who also answered above. In that case it is Al2(SO4)3.xH2O and the x can be any amount of moles of water. The case wherein you talk about Al2(SO4)3 is when you have anhydrous/dry aluminiumsulphate.
Formula For Aluminum Sulfate
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