# Gravimetric analysis of the chloride content of an asteroid gave 13.85% ""^35Cl "(isotopic mass = 34.97 amu)", and 86.14% ""^37Cl "(isotopic mass = 36.97 amu)". What is the isotopic mass of chlorine in the asteroid?

May 29, 2017

The $\text{local atomic mass}$ is $36.69$ $\text{amu}$.......

#### Explanation:

The atomic mass is the WEIGHTED average of the individual isotopes..........""^35Cl, and ""^37Cl.........

And thus the atomic mass for this asteroid............

$\left(34.97 \times 0.1385 + 36.97 \times 0.8614\right) \cdot \text{amu}$

$=$ $36.69 \cdot \text{amu} .$

This site reports that on Earth, the isotopic ratio is ""^35Cl, 76%, and ""^37Cl, 24%, which gives the atomic mass we generally use, i.e. $C l$, $35.45 \cdot g \cdot m o {l}^{-} 1$............