Question

Haemoglobin contains $0.25\%$ iron by mass. The molar mass of haemoglobin is $89600$. Number of iron atoms present in one mole of haemoglobin is:

Answer 1

Mass of iron in one mole of Haemoglobin $=\frac{89600\times 0.25}{100}=224$ g/mol.
As we know, molar mass of iron is $56$ g/mol.

So, number of iron atoms in one mole of Haemoglobin $\frac{224}{56}=4$.