Hello, H
The first step is to determine the % Ca in CaCO3. The formula, CaCO3, allows us to calculate that in the following manner:
Element Atomic Mass # of atoms Total (AM * #) Percent
Ca 40 1 40 40
C 12 1 12 12
O 16 3 48 48
Total 100
[The calculation was made simple by the fact that the molar mass of calcium carbonate is 100, so the % mass contribution is fortuitously equal to the total mass of each element.]
The mass of CaCO3 extracted is 1.25 g. The mass of Ca in that mass is 40% of 1.25 g, or 0.5 grams. Since the intact pill's mass was 2.5 g, the percent Ca in that amount is (0.5g/2.5g)*100%, or 20%.
Bob
