Chlorine has two isotopes, 35Cl and 37Cl that have the respective percent abundance's of 75.77% and 24.23% and masses of 34.9688 amu and 36.9659 amu. Calculate the atomic weight of chlorine.

The answer to your question is  35.4527 g

Explanation:

Data

Cl-35    abundance = 75.77 %    mass Cl-35 = 34.9688

Cl-37     abundance = 24.23 %   mass Cl-37 = 36.9659

Process

1.- Convert the percents to decimals

   75.77% = 75.77/100 = 0.7577

   24.23% = 24.23/100 = 0.2423

2.- Find the atomic weight

    Average atomic weight = Abundance 1 x Mass Cl-35 +

                                               Abundance 2 x Mass Cl-37

Substitution

     Average atomic weight = (0.7577)(34.9688) + (0.2423 x 36.9659)

Simplification

     Average atomic weight = 26.4959 + 8.9568

Result

      Average atomic weight = 35.4527 g