Question

Chlorine has two naturally occuring isotopes - chlorine-35 and chlorine-37. Elaborate on how the atomic mass is determined given that chlorine-35 has an abundance of 75.78% and has a mass of 34.969 amu and that chlorine-37 has an abundance of 24.22% and a mass of 36.966 amu.

Answer 1

Answer : Chlorine will have atomic mass as 35.452 amu

Explanation : To find the atomic mass of Chlorine, we can use the below formula;

Average atomic mass = ∑ (Percent abundance x mass of isotope) / 100

Now, here we have the values of Cl-35 with 75.78% abundance and mass as 34.969

and Cl-37 has 24.22% abundance and mass as 36.966

Substituting these values in the above equation,

Average atomic mass = (75.78 X 34.969) + (24.22 X 36.966) / 100

On solving we get the answer as, Average atomic mass = 35.452 amu.

Answer 2

Ar (Cl) = 34.969 * 75.78/ 100 + 36.966 * 24.22/ 100= 35, 45 :)