November's birthstone is citrine, a yellow member of the quartz family. It is primarily silicon dioxide, but small amounts of iron(III) ions give it its yellow color. A high quality citrine containing about 0.040 moles of SiO2 costs around $225. If this stone were pure SiO2, how many carats would it weigh? (There are exactly 5 carats per gram)
0.04 mols SiO2 x molar mass SiO2 = grams SiO2.
Then ? g SiO2 x (5 carats/1 g) = ? carats.