To find the percentage by mass of oxygen (O) in Ca2(SO4)3 (calcium sulfate), we first need to calculate the molar mass of the compound.
Molar mass of Ca2(SO4)3:
Ca: 2 x 40.08 g/mol = 80.16 g/mol
S: 3 x 32.06 g/mol = 96.18 g/mol
O: 12 x 16.00 g/mol = 192.00 g/mol
Total molar mass = 80.16 + 192.00 = 272.16 g/mol
Calculate the percentage by mass of oxygen:
Oxygen's contribution to the molar mass: 192.00 g/mol
Total molar mass of the compound: 272.16 g/mol
Percentage by mass of oxygen = (192.00 / 272.16) x 100% ≈ 70.59%
Therefore, the percentage by mass of oxygen in Ca2(SO4)3 is approximately 70.59%.
