The average atomic mass of a sample of an element X is 16.2 `mu`. What is the percentage of each isotope `overset(18)underset(8)X` and `overset(18)underset(8)X` in the sample?

Explanation

Let the percentage of `overset(16)underset(8)X` isotope = x
The percentage of `overset(18)underset(8)X` isotope = 100-x
Based on the data the average atomic mass of element
`=(16xxx)/(100)+(18xx(100-x))/(100)`
The given average atomic mass of the element = 16.2 u
`therefore (16xxx)/(100)+(18xx(100-x))/(100)=16.2`
16x+1800-18x=16.2
16x+1800-18x=1620
-2x=1620-1800=-180
`x=(-180)/(-2)=90`
percentage of `overset(16)underset(8)X` isotope =90%
Percentage of `overset(18)underset(8)X` isotope =10%