Question

In 1985 benitoite became the California “state gemstone.” Found only in a tiny mine near Coalinga, California, it is a silicate of barium and titanium with trace impurities that cause a range of hues from colorless to blue to pink. Its general formula is BaTi(SiO3)3. If a 15-carat stone were pure BaTi(SiO3)3, how many moles of silicon would it contain?

Answer 1

1 carat = 0.2 g; therefore, 15 carats = 3 g.
Then mol = grams/molar mass = ? That gives you mols in the mineral. Since there are 3 mols of Si in 1 mole of the mineral, mols Si will be 3x mols in the mineral.