An element X has isotopic masses of 6 and 7. if the relative abundance is 1 to 12.5 respectively, what is the relative atomic mass of X?
A.
6.0
B.
6.1
C.
6.9
D.
7.0
Correct answer is C
Contribution by isotope 6 = 6 x 1 = 6
contribution by isotope 7 = 7 x 12.5 = 87.5
This contribution is made by 1 + 12.5 = 13.5 atoms
Relative atomic mass of = 87.5 + 6 = 93.5/13.5 = 6.9
