Question
Mon December 26, 2011 By: Akash Sundi
 

boron occurs in nature in form of two isotopes having atomic masses 10 and 11.what are the percentage abundances of these isotopes in a sample boron having averag atomic mass 10.8.please explain.

Expert Reply
Mon December 26, 2011

The percent abundance can be calculated by using the formula:

Average atomic weight of the element =  (exact weight of isotope 1) X (abundance of isotope 1) + (exact weight of isotope 2) X (abundance of isotope 2)

Let the abundance of B-10 be assigned 'x' and the B-11 be '1 - x.'

So, (x) (10) + (1 - x) (11) = 10.8

10x + 11 - 11x = 10.8

x = 0.2

1 - x = 0.8

So, the percent abundance of B-10 is 20% and of B-11 is 80%.

 

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