Naturally occurring chlorine consists of two isotopes whose atomic weights are 35 and 37. The atomic weight of natural chlorine is 35.5, then what is the ratio of Cl35 to Cl37?
3 : 1
Let us consider the sum of percent abundance of Cl35 and Cl37 is equal to 100
So abundance of Cl35 is x and for Cl37 is 100-x
Atomic weight of Cl35 =34.96
Atomic weight of Cl37 =36.96
Atomic weight of Cl =35.45
Average atomic mass=34.9689(x)+36.9695(100−x)100=35.45
From here x= 76%
Abundance of Cl35 = 76%
Abundance of Cl37 = 24%
Hence, the ratio of Cl35 and Cl37 is 3:1 (approx.)