The percent mass of Calcium

Question

What is the percent mass of calcium in a calcium supplement if 1.41-g of calcium carbonate is extracted from a 2.65-g pill?

Answer 1

% mass Ca = mass Ca / total mass of pill

Total mass of pill = 2.65 g

Mass of Ca:

molar mass CaCO3 = 100 g / mol

atomic mass Ca = 40.1 g / mol

% Ca in CaCO3 = 40.1 g / 100 g (x100%) = 40.1%

mass Ca = 40.1% x 1.41 g = 0.565 g Ca

% mass Calcium = 0.565 g / 2.65 g (x100%) = 21.3%