Question

Given that the abundances of isotopes ⁵⁴Fe, ⁵⁶Fe and ⁵⁷Fe
are 5%, 90% and 5%, respectively, the atomic mass of Fe is
(a) 55.85 (b) 55.95 (c) 55.75 (d) 56.05

Answer 1

The atomic mass of Fe is 55.95 amu.

Explanation:

Given data:

Abundance of Fe⁵⁴ = 5%

Abundance of Fe⁵⁶ = 90%

Abundance of Fe⁵⁷ = 5%

Atomic mass of Fe = ?

Solution:

Atomic mass  = (abundance of 1st isotope × its atomic mass) + (abundance of 2nd isotope × its atomic mass + (abundance of 3rd isotope × its atomic mass)  / 100

Atomic mass  = (5×54)+(90×56)+(5×57) /100

Atomic mass =  270 + 5040 + 285 / 100

Atomic mass  = 5595/ 100

Atomic mass =  55.95 amu.