What is the average atomic mass of silicon?

Given the following data, calculate the average atomic mass of silicon.

isotope = Si-28
amu =27.9769
abundance(%) =92.18

isotope = Si-29
amu =28.9765
abundance(%) =4.71

isotope =Si-30
amu =29.9738
abundance(%) =3.12

Answer 1

Multiply the amu by the percentage of occurrence to arrive at an average atomic mass of #28.0891#

We obtain a weighted average by taking the amu of each isotope and multiplying it by the occurrence percentage:

#27.9769xx.9218+28.9765xx.0471+29.9738xx.0312# (quick note - there is a bit of rounding in here - the abundance percentages add up to 1.01, so the number we calculate is going to be slightly off).

This reduces to:

#25.7891+1.3648+0.9352=28.0891#

Upon consulting "the internet" to confirm our response, I discovered 28.0855 u ± 0.0003 u; thus, the result computed for our query is fairly accurate.

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Answer 2

Noah Aldrich

About 28.0855 atomic mass units (amu) make up the average atomic mass of silicon.

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Answer from HIX Tutor

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.

What is the average atomic mass of silicon?

Given the following data, calculate the average atomic mass of silicon. isotope = Si-28 amu =27.9769 abundance(%) =92.18 isotope = Si-29 amu =28.9765 abundance(%) =4.71 isotope =Si-30 amu =29.9738 abundance(%) =3.12

Given the following data, calculate the average atomic mass of silicon.

isotope = Si-28
amu =27.9769
abundance(%) =92.18

isotope = Si-29
amu =28.9765
abundance(%) =4.71

isotope =Si-30
amu =29.9738
abundance(%) =3.12