What is the mass in grams of 100 atoms of carbon - 12 isotope?

100 atoms is the same as how many moles?

nº atoms / avogadre number = nº of moles

100/6,022x10^23 = 1,66x10^-22 moles

the molar mass is: mass/moles

we know that the molar mass of carbon 12 it's the same as his atomic number, which is 12.

So, using the previous formula:

12 = mass / 1,66x10^-22

mass = 1,992x10-21 grams of carbon 12