Question

Element X has 3 naturally occurring isotopes. The first isotope has an atomic mass of 28.0 amu and a natural abundance of 14.0%. The second isotope has an atomic mass of 29.0 amu and a natural abundance of 66.0%. The third isotope has an atomic mass of 27.4 amu and a natural abundance of 20.0%. What is the atomic mass of element X?
a-27.1 amu
b-28.5 amu
c-28.9 amu
d-29.1 amu

Answer 1

Answer:

Option B. 28.5 amu

Explanation:

The following data were obtained from the question:

Isotope A:

Mass of A = 28.0 amu

Abundance (A%) = 14.0%

Isotope B:

Mass of B = 29.0 amu

Abundance (B%) = 66.0%

Isotope C:

Mass of C = 27.4 amu

Abundance (C%) = 20.0%

Atomic mass of element X =.?

The atomic mass of element X can be obtained by using the following formula:

Atomic mass = [(Mass of A × A%)/100] + [(Mass of B × B%)/100] + [(Mass of C × C%)/100]

Atomic mass of Element X = [(28 × 14)/100] + [(29 × 66)/100] + [(27.4 × 20)/100]

= 3.92 + 19.14 + 5.48

= 28.54 ≈ 28.5 amu

Therefore, the atomic mass of Element X is 28.5 amu