Question

What information is necessary to determine the atomic mass of the element chlorine?

Answer 1

Answer is: (3) the atomic mass and the relative abundance of each naturally occurring isotope of chlorine.

m(³⁵Cl) = 34.97 amu; the average atomic mass of chlorine-35.  

m(³⁷Cl) = 36.97 amu; the average atomic massof chlorine-37.

ω(³⁵Cl) = 75.76% ÷ 100% = 0.7576; fractional abudance of chlorine-35.

ω(³⁷Cl) = 24.24% ÷ 100% = 0.2424; fractional abudance of chlorine-37.

m(Cl) = m(³⁵Cl) · ω(³⁵Cl) + m(³⁷Cl) · ω(³⁷Cl).  

m(Cl) = 34.97 amu · 0.7576 + 36.97 amu · 0.2424.  

m(Cl) = 35.4548 amu; average atomic mass of chlorine.