Haemoglobin contains 0.25% iron by mass. The molar mass of haemoglobin is 89600. Number of iron atoms present in one molecule of haemoglobin are.. . .

% composition  =At.wt of the element×No. of atoms of the atom per molecuel ×100Molecular weight of the compound0.25 = 56×x×10089600x (No.of atoms of iron per molecule) = 4