Answer
0.09996 g
Work Step by Step
Mass of Co-59 = 58.9332
Mass of Co-60 = 59.9338
Average mass = 58.9332/59.9338
=58.9901
Fraction of the heavier isotope Co-60 = (58.9901 – 58.9332) / (59.9338 – 58.9332)
= 0.0569/1.0006
= 0.05687
Then, Fraction of the lighter isotope Co-59 = 1- 0.05687
= 0.9431
The mass of Co-60 in 1.7567 g of sample mixture = 1.7567 X 0.0569
