Question

If an element X has the two isotopes, 100x (80%) and 102X (20%), then weighted average atomic mass of the naturally occurring element X will be​

Answer 1

Answer:

100.4 u

Explanation:

$^{100}X$ ---> 80% abundance

$^{102}X$ ---> 20% abundance

Abundance of $^{100}X$ = (% abundance)*(At. mass) = $(\frac{80}{100})(100)$ = 80 u

Abundance of $^{102}X$ = (% abundance)*(At. mass) = $(\frac{20}{100})(102)$ = 20.4 u

So the average atomic mass becomes 80u + 20.4 u

= 100.4 u

Option (A)

Answer 2

Explanation:

Among the various options given in question statement the correct option is the first one

The calculation of above is as follow;

We consider the percentage of abundance of each isotope.

Weightage of 100x isotope = 100 * 80 = 8000

Weightage of 102x isotope = 102 * 20 = 2040

Adding both and taking out the average = (8000 + 2040) / 100

Average weight of element X would be = 100.4