The element iridium exists in nature as two isotopes: 191ir has a mass of 190.9606 u, and 193ir has a mass of 192.9629 u. the average atomic mass of iridium is 192.22 u. calculate the relative abundance (as percentages) of the two iridium isotopes.

The percentage abundance of and isotopes are 37.10% and 62.90% respectively.

Explanation:

Average atomic mass of an element is defined as the sum of masses of each isotope each multiplied by their natural fractional abundance.

Formula used to calculate average atomic mass follows:

  .....(1)

Let the fractional abundance of isotope be 'x'. So, fractional abundance of isotope will be '1 - x'

Mass of isotope = 190.9606 amu

Fractional abundance of isotope = x

Mass of isotope = 192.9629 amu

Fractional abundance of isotope = 1 - x

Average atomic mass of iridium = 192.22 amu

Putting values in equation 1, we get:

Percentage abundance of isotope =

Percentage abundance of isotope =

Hence, the percentage abundance of and isotopes are 37.10% and 62.90% respectively.