Question

Element X has two isotopes. One isotope has a mass of 25 amu and a percent abundance of 75%. The other isotope has a mass of 29 amu and a percent abundance of 25%. What is the average atomic mass of Element X?

a. 29
b. 25
c. 28
d. 27
e. 26

Answer 1

The average atomic mass of Element X is 26 amu.

Step-by-step explanation:

To calculate the average atomic mass of Element X, we need to multiply the mass of each isotope by its percent abundance and then sum the products. The first isotope has a mass of 25 amu and a percent abundance of 75%, so its contribution to the average atomic mass is (25 amu * 0.75) = 18.75 amu. The second isotope has a mass of 29 amu and a percent abundance of 25%, so its contribution to the average atomic mass is (29 amu * 0.25) = 7.25 amu. Adding these contributions together, we get an average atomic mass of (18.75 amu + 7.25 amu) = 26 amu.