Question

Find the average atomic mass of the element, given the isotopic percentage of 75.0% for cl35 and 25.0% for cl-37.

Answer 1

The  average atomic mass of the element = 35.5

calculation

average atomic mass =  sum of the masses of its isotope each multiplied by its natural abundance.

that is

[(75 x35) +(25 x37)] /100 = 35.5