Naturally occurring element X exists in three isotopic forms: X-28 (27.979 amu,92.21% abundance),X-29 (28.976 amu,4.70% abundance),and X-30 (29.974 amu,3.09% abundance).Calculate the atomic weight of X.
A)29.09 amu
B)28.09 amu
C)35.29 amu
D)86.93 amu
E)25.80 amu

Question

Quizplus · Accepted Answer

The atomic weight of X can be calculated by multiplying the mass of each isotope by its relative abundance (expressed as a fraction), then summing these products. For X-28: 27.979 amu * 0.9221 = 25.789; for X-29: 28.976 amu * 0.047 = 1.3619; for X-30: 29.974 amu * 0.0309 = 0.926. Adding these together gives 28.0769 amu, which rounds to 28.09 amu.

Naturally Occurring Element X Exists in Three Isotopic Forms: X-28