Silver has two stable isotopes with masses of 106.90509 u and 108.9047 u.The atomic weight of silver is 107.868 u.What is the percent abundance of each isotope?

Question

Quizplus · Accepted Answer

Let x be the percent abundance of Ag-107 and (100-x) be the percent abundance of Ag-109.

Using the atomic weight formula:

107.868 u = (106.90509 u)(x/100) + (108.9047 u)((100-x)/100)

107.868 u = 106.90509x/100 + 108.9047 - 108.9047x/100

107.868 u = 106.90509x/100 + 108.9047 - 1.089047x

1.089047x - 106.90509x/100 = 108.9047 - 107.868 u

1.089047x - 1.069051x = 1.0367 u

0.019996x = 1.0367 u

x = 51.8

So the percent abundance of Ag-107 is 51.8% and the percent abundance of Ag-109 is 48.2%. Therefore, the correct answer is B.

Silver Has Two Stable Isotopes with Masses of 106