Question

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

Answer 1

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