The gram formula mass of Al2(SO4)3 is 342.15 grams per mole. Aluminum sulphate, also known as alum, is a white crystalline substance that is commonly used in the purification of water.
The molecular weight of Al2(SO4)3 can be obtained by using the atomic weights of the atoms making up the molecular formula. The atomic weights of aluminum, sulphur and oxygen are 26.9815, 32.066 and 15.9994 respectively. The molecular weight of a substance expressed in grams is called a mole. Hence, 1 mole of Al2(SO4)3 is 342.15 grams of aluminum sulphate.
Aluminum sulphate is prepared by the reaction of aluminum hydroxide with sulphuric acid.