Question

What is the mass of chlorine-37 (24.23%), if the mass of chlorine-35 (75.77%) is 34.969g and the atomic mass of chlorine is 35.453 g?

Answer 1

Relative atomic mass (A_r) = (relative isotopic mass X1 × %X1 + relative isotopic mass X2 × %X2) / 100

Thus,

A_r(Cl) = (mass of Cl-35 × % abundance of Cl-35 + mass of Cl-37 × % abundance of Cl-37) / 100

35.453 = (34.969 × 75.77 + mass of Cl-37 × 24.23) / 100

3545.3 = 2649.6 + mass of Cl-37 × 24.23

895.7 = mass of Cl-37 × 24.23

mass of Cl-37 = 36.966 g

Answer: The mass of chlorine-37 is 36.966 g