Answer:
63.6 g/mol
Explanation:
If the percent abundance of Cu-63 is 69.1%, then Cu-65 is 30.1% since
100%-69.1%= 30.1%
To find the average atomic mass, multiiply the percentage with the corresponding mass then add the answers together.
(63 x 69.1%) + (65 x 30.1%) = average atomic mass
(63 x .691) + (65 x .301) = 43.533 + 20.085 = 63.618 g/mol = 63.6 g/mol
