An element,X,has the following isotopic composition: X-200,90%; X-199,8.0%; and X-202,2.0%.Its average atomic mass is closest to
A)200 amu.
B)203 amu.
C)199 amu.
D)202 amu.
E)201 amu.

Question

Quizplus · Accepted Answer

The average atomic mass is calculated by multiplying the mass of each isotope by its relative abundance (expressed as a fraction), then summing these products. For element X: (200*0.90) + (199*0.08) + (202*0.02) = 180 + 15.92 + 4.04 = 199.96 amu, which is closest to 200 amu.

An Element,X,has the Following Isotopic Composition: X-200,90%; X-199,8