Question

Nitrogen has an atomic mass of 14.0067, its naturally occuring isotopes are 14N (14.003) and 15N (15.001). What are the relative abundance of each isotope?

Answer 1

Nitrogen has an atomic mass of 14.0067 u.

Let one of its isotope having atomic mass 14.003 u has natural abundance of x %.

Other isotope having atomic mass 15.001 u has natural abundance of (100-x) %.

$(x×14.003 + (100-x)× 15.001)/100 =14.0067$

$14.003x +1500.1 -15.001x = 1400.67$

$0.998x=99.43$

$x = 99.43/0.998$

$x = 99.629$

$100-x =0.371$

Relative abundance of isotope having atomic mass 14.003 is 99.629 %(Ans)

The other isotope has abundance of 0.371 %(ans)