Answers

2016-04-22T18:05:55+05:30
0.25 % by mass means 0.25 gms of iron in 100 gms of haemoglobin
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therefore in 89600 gms i.e. 1 mole of haemoglobin contains:  0.25 x 89600 = 896 x 0.25 = 224 gms of fe                           
But 1 mole of Fe i.e. 56 gms contains 6.023 x  10^{23} ( Avogadro 's number) atoms.

therefore 224 gms of Fe will contain:  224 x 6.023 x 10^{23}  = 2.409 x 1024 atoms.

you can take NA as 6.022*10^23 also
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