Answer:Our formula for percent composition is:
Molar mass of element
----------------------------------- x 100
Molar mass of compound
So, lets find the molar mass of the compound as a whole before we begin. We do this by adding atomic masses from the periodic table.
Ca: 40.078
S: 32.065
O4: 63.996 (15.999 x 4)
To find our total mass, all we need to do is add those numbers together! Our molar mass of CaSO4 is 136.139 g/mol.
Now, lets use those individual masses and our total mass in the equation to find the percent composition of each element.
Ca: 40.078
---------- equals .294, and when we multiply that by 100 we get 29.44%
136.139
The percent composition of calcium in CaSO4 is 29.44%.
S: 32.065
------------- equals .235, and when we multiply that by 100 we get 23.55%
136.139
The percent composition of S in CaSO4 is 23.55%.
O4: 63.996
------------- equals .470, and when we multiply that by 100 we get 47.0%
136.139
The percent composition of O4 in CaSO4 is 47%.
Hope this helps!