Question

A scientist discovers three isotopes of an unknown element. Isotope A has a mass of 28.776g and an abundance of 15.7%, isotope B has a mass of 25.992g and an abundance of 1.3%, and isotope C has a mass of 27.004g and an abundance of 83.0%. Calculate the average atomic mass of the unknown element. Show all of your work and include the correct units in your answer.

Answer 1

`\huge\boxed{\sf Average \ Atomic \ Mass=27.269 \ amu}`

Step-by-step explanation:

Given Data:

Isotope A mass = 28.776 g

Isotope A abundance = 15.7%

Isotope B mass = 25.992 g

Isotope B abundance = 1.3%

Isotope C mass = 27.004 g

Isotope C abundance = 83%

Required:

Average Atomic Mass = ?

Formula:

`\displaystyle Average \ Atomic \ Mass = (Isotope \ A(mass * abun) + B(mass * abun)+C(mass * abun))/(100)`

Solution:

`\displaystyle Average \ Atomic \ Mass = (28.776* 15.7 +25.992 * 1.3+27.004 * 83 )/(100) \\\\Average \ Atomic \ Mass=(451.7832 + 33.7896+2241.32)/(100) \\\\Average \ Atomic \ Mass=(2726.9)/(100) \\\\Average \ Atomic \ Mass=27.269 \ amu\\\\\rule[225]{225}{2}`