Question.
If bromine atom is available in the form of $\mathrm{Br}^{79}, \mathrm{Br}^{81}$, say, two isotopes $(49.7 \%)$ and $(50.3 \%)$, calculate the average atomic mass of bromine atom.
If bromine atom is available in the form of $\mathrm{Br}^{79}, \mathrm{Br}^{81}$, say, two isotopes $(49.7 \%)$ and $(50.3 \%)$, calculate the average atomic mass of bromine atom.
Solution:
It is given that two isotopes of bromine are $(49.7 \%)$ and $(50.3 \%) .$ Then, the average atomic mass of bromine atom is given by :
$\therefore$ Average atomic mass of Br
$=\frac{49.7 \times 79+50.3 \times 81}{100}=\frac{3926.3+4074.3}{100}$
$=39.263+40.743=80.006 \mathrm{u} .$
It is given that two isotopes of bromine are $(49.7 \%)$ and $(50.3 \%) .$ Then, the average atomic mass of bromine atom is given by :
$\therefore$ Average atomic mass of Br
$=\frac{49.7 \times 79+50.3 \times 81}{100}=\frac{3926.3+4074.3}{100}$
$=39.263+40.743=80.006 \mathrm{u} .$