1.9 Calculate the atomic mass (average) of chlorine using the following data:

  % Natural Abundance Molar Mass
35Cl  75.77 34.9689
37Cl  24.23 36.9659

NEETprep answer:  

The average atomic mass of chlorine

 =Fractionalabundance
ofCl35Molarmass
ofCl35+Fractional
abundance
ofCl37Molarmass
ofCl37
=75.7710034.9689u+24.2310036.9659u

= 26.4959 + 8.9568
= 35.4527 u
 The average atomic mass of chlorine = 35.4527 u