*The answer might be different if you are using a different Periodic Table, but it should be similar. Al2(SO4)3 2 Aluminum atoms 3 Sulfur atoms 12 Oxygen atoms Find the mass of Al2(SO4)3 Aluminum = 26.98 g Sulfur = 32.07 g Oxygen = 16.00 g 2(26.98)+3(32.07)+12(16.00) 53.96+96.21+192.0 342.2 g = mass of Al2(SO4)3 Divide the total mass of Sulfur atoms in the molecule by the mass of the molecule 96.21/342.2 0.2812 Multiply by 100 to have a percentage. 28.12 The mass percent composition of Sulfur in Al2(SO4)3 is 28.12%.
