# 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

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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%

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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