posted by Jenn .
If you have a tank containing 10,000L of water. what weight of CaSO4.H2O must be added to math the Ca+ concentration of 130ppm
in 10,000L water, that is 10E6 grams. So you must have 130ppm then 1.3kg Ca++ ion.
moles Ca ion= 1300/40
now, find the weight (I assume the writer means mass) of CaSO4.H2O of that same number of moles.