Question

The atomic mass of chlorine is listed as 35.454 amu on the periodic table. It has two naturally occurring isotopes, Cl-35 and Cl-37. What are the approximate percentages of each?

Answer 1

x=percentage of Cl-35
(1-x)=percentage of Cl-35

35(x)+37(1-x)=35.454
35x+37-37x=35.454
-2x=35.454-37
-2x=-1.546
x=-1.546/(-2)
x=0.773

0.773=77.3/100=77.3%

(1-x)=1-0.773=0.227

0.227=22.7/100=22.7%

answer: the percentages are: 77.3% of Cl-35 and 22.7% of Cl-37.