mass of a atom of c-12

Question

what is the mass of the carbon-12 atom? in finding the mass is there use of 6.022*10²³ or not 

Answer 1

C-12 is used as the standard from which the atomic masses of all other nuclides are measured. The atomic mass of C-12 is 12.000000 u (u = atomic mass units). The atomic mass unit is defined as 1/12th the mass of a neutral C-12 atom. Since C-12 is used as the reference mass, no other nuclides have whole number masses. Converting between atomic mass units and grams (microscopic to macroscopic mass) requires the use of Avogadro's constant (6.022*10^23 mol^-1) which is the number of atoms/molecules in one mole of a substance. Avogadro's number, 6.022*10^23, is the number of atoms in 12 g of C-12. Converting between u and grams for one atom of any substance is completed by the conversion factor:

1 u = M_u/N_A = molar mass constant/avogadro's constant = (1g/mol)/6.022*10^23 mol^-1. 

Notice that mols cancels out and leaves you with grams for the units. 

Answer 2

Hello, thank you for taking the time to post your question!

You do end up using the 6.022 x 10^23 number in order to convert it over. The idea is that to find the mass of a single atom you want to take the mass of one mole by the number of atoms in that mole. For carbon-12, that means taking

12 g/mol / (6.022 x 10^23) = 1.9927 x 10^(-23) g/atom C-12

I hope that helps you get moving in a better direction on this type of question! Feel free to reach out if you have any additional questions beyond that :)