What is the percent mass of calcium in a calcium supplement if 1.40-g of calcium carbonate is extracted from a 2.13-g pill?

Answer 1

Find mass of calcium in 1.40 g CaCO3 and then divide that by 2.13 g (x100%) to get %Ca in the pill.

1.40 g CaCO₃ x 1 mole CaCO₃/100.0869 g x 1 mol Ca/mole CaCO3 x 40.078 g Ca/mol Ca = 0.5606 g Ca

0.5606 g Ca/2.13 g (x100%) = 26.3% calcium in the pill