(i) How would you define the terms atomic mass and molecular mass ?
(ii) Nitrogen occurs in nature in the form of two isotopes with atomic masses 14 and 15 respectively. If the average atomic mass of nitrogen is 14.0067, what is the percent abundance of the two isotopes ?

Explanation

Let % abundance of N-14 isotope = x
Then % abundance of N-15 isotope = (100 - x)
`"The average atomic mass" = ( (14x+ (100-x)15)/(100))= 14.0067` or x = 1400.67 – 1500 = -99.33 or x = 99.33
Thus, % abundance of N-14 isotope = 99.33% % abundance of N-15 isotope = 0.67%