Question

1. A hypothetical element consists of 3 isotopes
with the following masses and natural abundances.
Isotopic Natural
Mass Abundance
Number %
1 39 78.8
2 40 18.1
3 41 3.1
What is the atomic weight?
A. 40.9

B. 39.9

C. 39.2

D. 40.1

2. A hypothetical pure element consists entirely of two isotopes. The natural percent abundance of the isotope with mass 25.6 u is 51.7%.The other isotope has mass 29.8 u. Calculate the atomic weight of the naturally occurring element?