gravimetric analysis

Question

Calcium in tap water sample (0.20 L) was determined by precipitating the cation as CaC₂O₄. The precipitate then filtered, washed and ignited to form 0.1132g of CuO. Calculate the concentration of Ca in this sample

Answer 1

I assume that CuO was supposed to be CaO.

The mass of Ca in 0.1132g of CaO is gotten by

atomic mass of Ca/formula mass of CaO x 0.1132 g CaO

40.078/56.0770 x 0.1132 g CaO = 0.08090 g Ca

As this was in 0.2 L water, the concentration of Ca in mg per liter is 404.5 mg/L.