the avg. atomic mass of copper is 63.546u. Natural copper consists of two isotopes Cu63and Cu65. Their natural abundances are 69.09% and 30.91% respectively. If tha mass of Cu63is 62.9298u, what is the mass of Cu65??
Let the mass of Cu-65 = x u
62.9289x0.6909 + 0.3091x = 63.546
0.3091x = 63.546 - 62.2389
x = 1.3071 / 0.3091
x = 4.2287 u