Gravimetric analysis of the chloride content of an asteroid gave #13.85%# #""^35Cl# #"(isotopic mass = 34.97 amu)"#, and #86.14%# #""^37Cl# #"(isotopic mass = 36.97 amu)"#. What is the isotopic mass of chlorine in the asteroid?

1 Answer
anor277
May 29, 2017

The #"local atomic mass"# is #36.69# #"amu"#.......

Explanation:

The atomic mass is the WEIGHTED average of the individual isotopes..........#""^35Cl#, and #""^37Cl#.........

And thus the atomic mass for this asteroid............

#(34.97xx0.1385+36.97xx0.8614)*"amu"#

#=# #36.69*"amu".#

This site reports that on Earth, the isotopic ratio is #""^35Cl#, #76%#, and #""^37Cl#, #24%#, which gives the atomic mass we generally use, i.e. #Cl#, #35.45*g*mol^-1#............

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