The abundance of isotope 35 = 75%
The abundance of isotope 37 = 25%
Ratio isotope 35 : isotope 37 = 3 : 1
Further explanation
Given
Ar Cl = 35.5
Two isotopes of mass number 35 and 37
Required
The ratio of each isotope
Solution
If the abundance of isotope 35 is x%, then the abundance of isotope 37 is (100-x)%
35.5 = x%.35 + (100-x)%.37
35.5 = 0.35x+0.37(100-x)
35.5=0.35x-0.37x+37
0.02x=1.5
x=75