Question

the atomic mass of Cu is 63.546.two isotops of Cu is Cu(63) and Cu(65).what is the quantity of Cu(63) which is found in nature?

Answer 1

Let us denote the quantity of Cu(63) as x. Then
63x+65(1-x)=63.546
2x=1.454
x=0.727
Thus the quantity of Cu(63) in nature is 72.7%
Answers: 72.7%