Question

Boron exists in two isotopic form $B^{10}$ and $B^{11}$. If the average atomic weight of $B$ is $10.20u$, select the correct statement.

• A. $\%$ abundance of $B^{10}=\%$ abundance of $B^{11}$
• B. $\%$ abundance of $B^{10}>\%$ abundance of $B^{11}$
• C. $\%$ abundance of $B^{10}<\%$ abundance of $B^{11}$
• D. $\%$ abundance of $B^{10}=\frac{\%abundanceof{B}^{11}}{2}$

Answer 1

The correct option is B $\%$ abundance of $B^{10}>\%$ abundance of $B^{11}$

Let the percentage existence of $B^{10}$ isotope be $x$ . Therefore percentage existence of the $B^{11}$ isotope is $(100-x)$

mass of $B^{10}$ isotope is $10amu$.

mass of $B^{11}$ isotope is $11amu$.

Therefore,

$\frac{10+11(100-x)}{100}=10.2$

$10+11(100-x)=1020$

$x=80

Therefore the percentage of $Boron-10$ isotope is $80$%

and $Boron-11$ isotope is $(100-x)=20$%

Hence, option B is the correct answer.