The first step to solve this problem is to find the number of moles of CaSO₄ that we have in a sample of 49.5 g of it. To do that we will find the molar mass of CaSO₄. We have to look for the atomic mass of each element that is present in the molecule.
Ca: 40.08 amu
S: 32.07 amu
O: 16.00 amu
Using that information we can find the molar mass of CaSO₄.
molar mass of CaSO₄ = 40.08 + 32.07 + 4 * 16.00
molar mass of CaSO₄ = 136.15 g/mol
Using the molar mass we can find the number of moles of CaSO₄ that we have in a sample of 49.5 g of it.
number of moles of CaSO₄ = 49.5 g / (136.15 g/mol)
number of moles of CaSO₄ = 0.360 moles
In one mol of molecules of CaSO₄ we have 1 mol of atoms of S (since there is 1 atom of S in one molecule of CaSO₄). Let's use that relationship to find the number of moles of S atoms that there are in 0.360 moles of CaSO₄.
number of moles of S = 0.360 moles of CaSO₄ * 1 mol of S/ (1 mol of CaSO₄)
number of moles of S = 0.360 moles
Finally we can find the mass of S using the molar mass of O.
molar mass of S = 32.07 g/mol
mass of S = 0.360 moles * 32.07 g/mol
mass of S = 11.55 g
Answer: the mass of sulfur in a 49.5 g sample of CaSO₄ is 11.55 g