Calculate the average atomic mass of an element containing 39.9% of atoms with a mass of 69 amu and 60.1% of atoms with a mass of 71 amu. Show your work for credit and round your answer to one decimal place.

70.202 amu

Explanation:

From the question given above, the following data were obtained:

Isotope A:

Abundance (A%) = 39.9%

Mass of A = 69 amu

Isotope B:

Abundance (B%) = 60.1%

Mass of B = 71 amu

Average atomic mass =?

The average atomic mass of the element can be obtained as follow:

Average atomic mass = [(Mass of A × A%)/100] + (Mass of B × B%)/100]

= [(69 × 39.9)/100] + [(71 × 60.1)/100]

= 27.531 + 42.671

= 70.202 amu

Therefore, the average atomic mass of the element is 70.202 amu