7. Iron has 2 isotopes, Fe - 55 with an abundance of 15.35% and Fe - 56 with an abundance of 84.65%. What is the average atomic mass of iron?

Average atomic mass  = 55.85 amu

Explanation:

Given data:

Abundance of Fe-55 = 15.35%

Abundance of Fe-56 = 84.65%

Average atomic mass = ?

Solution:

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

Average atomic mass = (15.35×55)+(84.65×56) /100

Average atomic mass =  844.25 + 4740.4/ 100

Average atomic mass = 5584.65 / 100

Average atomic mass  = 55.85 amu.

the answer is 75.0%.

a