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zheka24 [161]
3 years ago
5

in a sample of silcon 92.21% of the atoms have a mass of 27.98 amu, 4.70% have a mass of 28.98 amu and 3.09% have a mass of 29.9

7 amu. what is ther average atomic mass of the sample? socratic.org socratic.org
Chemistry
1 answer:
oksano4ka [1.4K]3 years ago
5 0

Answer: 28.1 amu

Explanation:

Mass of isotope 1 = 27.98 amu

% abundance of isotope 1 = 92.21% = \frac{92.21}{100}=0.9221

Mass of isotope 2 = 28.98 amu

% abundance of isotope 2 = 4.70% = \frac{4.70}{100}=0.047

Mass of isotope 3 = 29.97 amu

% abundance of isotope 2 = 3.09% = \frac{3.09}{100}=0.0309

Formula used for average atomic mass of an element :

\text{ Average atomic mass of an element}=\sum(\text{atomic mass of an isotopes}\times {{\text { fractional abundance}})

A=\sum[(27.98 )\times 0.922+(28.98)\times 0.047+(29.97)\times 0.0309]

A=28.1amu

Therefore, the average atomic mass of silicon is 28.1 amu

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