How many oxygen atoms are in 3.60 g of quartz?

7.226 x 10^22 oxygen atoms

EXPLANATION :

we know that 1 mole of anything is 6.022 x 10^23 of that thing.

The formula of Quartz is SiO2. So, 1 mole of Quartz will have 2 moles of oxygen atoms, i.e. 2 x 6.022 x 10^23 atoms of oxygen.

The molar mass of quartz is 60 g per mol. So, 60 g quartz means 1 mole quartz. We are given 3.6 g quartz,

60 g quartz means 1 mole quartz or 2 x 6.022 x 10^23 oxygen atoms.

then 3.6 g quartz will have oxygen atoms equal to (2 x 6.022 x 10^23 x3.6) / 60 =  0.7226 x 10^23 oxygen atoms or 7.226 x 10^22 oxygen atoms.