Answer:
The correct answer is option b.
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)
We are given:
Mass of isotope X-28 = 27.979 amu
Percentage abundance of isotope X-28 = 92.21%
Fractional abundance of isotope X-28 = 0.9221
Mass of isotope X-29 = 28.976 amu
Percentage abundance of isotope X-29 = 4.70%
Fractional abundance of isotope X-29 = 0.047
Mass of isotope X-30= 29.974 amu
Percentage abundance of isotope X-30 = 3.09%
Fractional abundance of isotope X-30 = 0.0309
Putting values in equation 1, we get:
The atomic weight of X is 28.09 amu.