Question

An element has 2 common isotopes. The first isotope has a mass of 68.926 amu and occurs 60.10% of the time. The second isotope has a mass of 70.925 amu and occurs 39.90 % of the time. Calculate the atomic mass of this element.

Answer 1

The atomic mass of element X is 69.724 amu

Step-by-step explanation:

Given data:

Atomic mass of element X= ?

Percent abundance of X-68.926 = 60.10%

percent abundance of X-70.925 = 39.90%

Solution:

Average atomic mass = (abundance of 1st isotope × its atomic mass) +(abundance of 2nd isotope × its atomic mass) / 100

Average atomic mass = (68.926×60.10)+(70.925×39.90) /100

Average atomic mass = 4142.4526 +2829.9075/ 100

Average atomic mass = 6972.3601 / 100

Average atomic mass = 69.724 amu.

The atomic mass of element X is 69.724 amu.