The recommended daily allowance (rda of calcium is 1.2 g. calcium carbonate contains 12.0% calcium by mass. how many grams of calcium carbonate are needed to provide the rda of calcium?

1) Calcium carbonate contains 40.0% calcium by weight.

M (CaCO₃) = 100.1 g/mol

M (Ca) = 40.1 g/mol

w (Ca) = 40.1/100.1=0.400 (40.0%) !

2) Mass fraction of this is excessive data.

3) The solution is:

m (Ca) = 1.2 g

m (CaCO₃) = M (CaCO₃) * m (Ca) / M (Ca)

m (CaCO₃) = 100.1g/mol*1.2g/40.1g/mol=3.0 g