Question

Chlorine has two common isotopes ${}^{35}Cl$ and${}^{37}Cl$, if the abundance of ${}^{35}Cl$ is $75.2$ and that of ${}^{37}Cl$ is $24.8$, what is the average atomic mass of chlorine?

Answer 1

Abundance of ${}^{35}Cl=75.2=\frac{35\times 75.2}{100}$

Abundance of ${}^{37}Cl=24.8=\frac{24.8\times 37}{100}$

Average atomic mass= $\frac{35\times 75.2}{100}+\frac{24.8\times 37}{100}$

$=35.5u$ .