Question

There are two isotopes of an element with atomic mass z. Heavier on has atomic mass z+2 and lighter one has z-1, then abundance of lighter one is
A. `66.6%`
B. `96.7%`
C. `6.67%`
D. `33.3%`

Answer 1

Correct Answer - A
Let percent abundance of lighter isotope = x
`:. (x(z-1)+(100-x)(z+2))/(100)=z`
`xz-z+100z+200-xz-2x=100z`
`-3x = -200`
`x = (200)/(6) = 66.6`
`:.` percent abundance of lighter isotopes = x