Copper, a metal known since ancient times, exists in two stable isotopic forms, 6329Cu (69.09%) and 6529Cu (30.91%). Their atomic masses are 62.93 amu and 64.9278 amu respectively. Calculate the average atomic mass of copper.

Wt. Avg. Atomic Weight => 63.35457 amu

Explanation:

Given              Isotopic             %Abundance     fractional          Wt Avg

                  At. Mass (amu)                                  abundance      contribution                    

Cu-63              62.93                      69.09              0.6909            43.4783

Cu-65              64.9278                  20.0668        0.200668        20.0668

Wt Average of all isotopes = ∑Wt Avg Contributions

=  43.4783 amu + 20.0668 amu = 63.35457 amu

number of molecules / avogadro's number * molecule molecular = mass

explanation:

we define a gram-molecular weight as the mass of one mole of any element or compound. a mole contains avogadro's number of units (molecules) –  

6.022

x

10

23

. so, dividing the number of molecules by avogadro's number gives us the number of moles. multiplying that by the molecular weight gives us the mass. from the periodic table we find the gram-molecular weight of u to be238 and of f to be19. so,  

u

f

6

will have a gram-molecular weight of 352g.

personal, she chose to do it.