Question

if the average atomic mass of an element having 2 isotopes is 71 the ratio of natural abundance of the 2 isotopes of mass 70&74 will be

Answer 1

let the no.of total atoms of the element is 100. no.of atoms having mass 74=(100-x)and no.of atoms having mass 70 =x.
Average mass of the element =71=> 74(100-x)+70x/100=> 7100=74(100-x)+70x=>74x-70x=7400-7100=
300=4x=> x=300/4=75. So isotope of 74 gms mass is 25% present and isotope of 70 gms mass is 75% present .