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Q.
The element chlorine consists of a mixture of $75.53$ and $24.47$ having a mass of $34.97$
amu and $36.95$ amu, respectively. The atomic weight of chloride is:
Bihar CECEBihar CECE 2001
Solution:
At. wt. of chlorine
$=\frac{\text { Abundance } \times \text { mass }+\text { Adundance } \times \text { mass }}{100}$
Given, abundance of $Cl ^{35}$ isotope $=75.53$
Mass of $C l^{35}$ isotope $=34.97$
Abundance of $C l^{37}$ isotope $=24.47$
Mass of $C l^{37}$ isotope $=36.95$
$\therefore $ At. wt. of chlorine
$=\frac{34.97 \times 75.53+24.47 \times 36.95}{100}$
$=\frac{3545.45}{100}$
$=35.45$