An average sample of chlorine contains 75.77% chlorine-35, with an atomic mass of 34.969 amu (atomic mass units), and 24.23% chlorine-37, with an atomic mass of 36.966 amu. What is the average atomic mass of chlorine?

Question

Naomi Aronson · Accepted Answer

You require the weighted average.

The total of each individual nuclide multiplied by its isotopic abundance yields the weighted average. Thus, we just perform the arithmetic: #0.7577xx34.969+0.2423xx36.966 = ???# amu Next, check to see how accurate your result is by looking at the Periodic Table.

Axel Alvarado · Answer

undefined The average atomic mass of chlorine is approximately 35.45 amu.

Axel Alvarado · Answer

undefined To find the average atomic mass of chlorine, you multiply the atomic masses of each isotope by their respective percentages and then add the products together.

Average atomic mass = (Percentage of chlorine-35 × Atomic mass of chlorine-35) + (Percentage of chlorine-37 × Atomic mass of chlorine-37)

= (0.7577 × 34.969 amu) + (0.2423 × 36.966 amu)

= 26.515433 amu + 8.9660898 amu

= 35.4815228 amu

Therefore, the average atomic mass of chlorine is approximately 35.48 amu.