Calculate the correct number of moles and formula units in 7.3x10^-3g of caso4

From the periodic table:
mass of calcium = 40 grams
mass of sulfur = 32 grams
mass of oxygen = 166 grams

Therefore:
molar mass of CaSO4 = 40 + 32 + 4(16) = 136 grams

number of moles can be calculated as follows:
number of moles = mass / molar mass
number of moles = (7.3 x 10^-3) / (136) = 5.367 x 10^-5 moles

The molecules contain like 54 of water 

Anions are negative charged ions