How many oxygen atoms are in 1.60 g of quartz? hints?

Quartz has the formula SiO2

From the periodic table:

mass of oxygen = 16 grams

mass of silicon = 28.0855 grams

Mass of one mole of quarts = 28.0855 + 2 (16) = 60.0855 grams

number of moles = mass / molar mass

number of moles = 1.6 / 60.0855 = 0.0266 moles

Each mole of quartz contains Avogadro's number of atoms.

Therefore:

number of atoms in 1.6 g = 1.6 x 6.02 x 10^23 = 1.603 x 10^22 atoms