Calculating the Abundance (percentage) of an Isotope

Calculating the Abundance (percentage) of an Isotope

Example: Copper consists of two isotopes, copper-63 and copper-65. Its relative atomic mass is 63.62. Find the abundance of each isotope.

Let y/100 = abundance of copper-63

Let (100-y)/100 = abundance of copper-65

63.62 = (y/100 x 63) + [(100-y)/100 x 65]

63.62 = 63y +6500 – 65y

-2y = -135

y = 69

Abundance of copper-63 = 69%

Abundance of copper-65 = 100 – 69 = 31%