4) solve problems

G. The natural isotopic abundance of^{ 10}B is 19.60% and ^{11}B is 80.40 %. The exact isotopic masses are 10.13 and 11.009 respectively. Calculate the average atomic mass of boron

**The answer is 10.81 u**

**Solution :**

Relative abundance of ^{10}B isotope = 19.60%

Relative abundance of ^{11}B isotope = 80.40%

\(Average\space atomic \space mass= {(Mass \space of\space isotope \space 1) \times ( Relative\space abundance \space of \space ^{10}B \space isotope) + (Mass \space of\space isotope\space 2) \times (Relative \space abundance of\space ^{11}B \space isotope \over 100}\)

=\((10 \times 19.6 ) + (11 \times 80.4 ) \over100\)

\(={196+ 884.4\over 100}={1080.4\over 100}\)

=10.804 u