Isotopic Abundance?

Question

Naturally occurring copper exists in two isotopic forms: 63Cu and 65Cu. The atomic mass of copper is 63.55 amu. What is the approximate natural abundance of 63Cu?

Answer 1

Use algebra, if Cu has two forms it will be a substitution equation.

(63 * X)+(65 * Y)=63.55
X + Y = 1.0

solve for

Y= 1 - X

Substitute

(63 * X) + (65 *(1- X)) = 63.55

then solve for X

Answer 2

Let the abundance of 63Cu = x and the abundance of 65Cu = 1-x.

Then, set up and solve the equation :

63(x) + 65 (1-x) = 63.55

That'll get you to the answer.