Question

Chlorine exists in two isotopic forms `Cl-37` and Cl-35 but its atomic mass is 35.5. this indicates the ratio of Cl-37 and Cl-35 is appromimately
A. `1 : 2`
B. `1 : 1`
C. `1 : 3`
D. `3 : 1`

Answer 1

Correct Answer - C
Let relative abundance of Cl-37 = x%
then relative abundance of Cl-35 = (100 - x)%
Average atomic mass `=(x xx37+(100-x)35)/100=35.5
rArr37x+3500-35x=3550rArrx=25
therefore" "100-x=75`
Thus, the ratio of Cl-37 and Cl-35 is x : (100 - x)
= 25 : 75 = 1 : 3