Answer: Boron -10 : 20%
Boron -11 : 80%
Explanation:
Mass of isotope boron -10= 10
% abundance of isotope 1 = x% = [tex]\frac{x}{100}[/tex]
Mass of isotope boron-11 = 11
% abundance of isotope 2 = (100-x)% = [tex]\frac{100-x}{100}[/tex]
Formula used for average atomic mass of an element :
[tex]\text{ Average atomic mass of an element}=\sum(\text{atomic mass of an isotopes}\times {{\text { fractional abundance}})[/tex]
[tex]10.8=\sum[(10)\times \frac{x}{100})+(11)\times \frac{100-x}{100}]][/tex]
[tex]x=20[/tex]
Therefore, percent of boron -10 is 20% and isotope boron-11 is (100-20)= 80%.