What is the average atomic mass of this sample of silicon?

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gsenviro | College Teacher | (Level 1) Educator Emeritus

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The relative abundance of silicon as per the mass spectrum is

92.21% of 27.97 amu, 4.79% of 28.97 amu and 3.09% of 29.97 amu.

The average atomic weight is calculated as the sum of products of relative abundance of various isotopes and their atomic mass.

i.e. Average atomic mass = 0.9221 x 27.97 + 0.0479 x 28.97+ 0.0309 x 29.97

 = 28.11 amu

Thus the analysis of mass spectrum reveals that the silicon atom has an average atomic mass of 28.11 amu.

Hope this helps.

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