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# HELP!!!! Percentage abundances watch

1. How do I calculate the percentage abundance of 10B in a naturally occuring sample of boron?
2. (Original post by B S V)
How do I calculate the percentage abundance of 10B in a naturally occuring sample of boron?
you need to know which isotopes are present and the relative mass (weighted average of the isotopic masses)
3. (Original post by charco)
you need to know which isotopes are present and the relative mass (weighted average of the isotopic masses)
Umm.... The question says:
In a sample, Boron exist as two isotopes 10B and 11B
Calculate the percentage abundance of 10B in this naturally occuring sample of Boron.
Therefore how would I answer this question?
4. (Original post by B S V)
Umm.... The question says:
In a sample, Boron exist as two isotopes 10B and 11B
Calculate the percentage abundance of 10B in this naturally occuring sample of Boron.
Therefore how would I answer this question?
You must use the relative mass.

relative mass = [(isotope mass1 x %abundance1) + (isotope mass2 x %abundance 2)]/100

and you know that

%abundance1 + %abundance2 = 100

You have two simultaneous equations with two unknowns - solve them.
5. Thank you very much, this has been very helpful!!,

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