Question

what will be the number of iron atom present per haemoglobin molecule when iron is present in .25 percentage ?

Answer 1

Your solution is as follows:

0.25 % by mass means:

0.25 gms of iron in 100 gms haemoglobin.

therefore in 89600 gms i.e. 1 mole of haemoglobin contains:  0.25 x 89600 = 896 x 0.25 = 224 gms of fe

                                                                                             100

But 1mole of Fe i.e. 56 gms comtains 6.023 x 1023 ( Avogadro number. NA) atoms.

therefore 224 gms of Fe will contain: 224 x 6.023 x 1023  = 2.409 x 1024atoms.