Hemoglobin contains 0 . 34 % of iron by mass. The number of Fe...

Mass of haemoglobin = $3 . 3g$

Mass of iron atoms = $\dfrac{0 . 34}{100} \times 3 . 3 = 0 . 01122g$

$56g$of iron contains = $1$ mole of iron or $6 . 023 \times {10}^{23}$ atoms

Number of moles of atoms=$\dfrac{Mass}{atomicmass}$

Number of moles of $0 . 01122g$ of iron is

Number of moles = $\dfrac{0 . 01122g}{56g} = 0 . 00020$ moles

Number of atoms =Number of moles $\times$avogadro number

No. of $Fe$ atoms

$= 0 . 00020 \times 6 . 022 \times {10}^{23} = 1 . 2046 \times {10}^{20}$