Question

haemoglobin contains 0.33% of Fe by wt. The molecular mass of haemoglobin is approximately 67200. The no. of Fe atoms ( at wt. of Fe 56) present in one molecule of Haemoglobin is

a) 6
b) 1
c) 4
d) 2


P.S. I don't want to get the answer or the formula ( i know them) I need to know the procedure of doing such questions :)

Answer 1

so what you have (0.33%) is the mass percent composition of iron.

What you wanna do if find the total weight (mass) of iron in the sample.

Then use good old \(n=\dfrac{m}{M}\) to find moles.

then use: \(n=\dfrac{N}{N_A}\) to find the number of atoms present.

Answer 2

do you mean to say that i need to find out
\[Fe = .33% *67200 \] gms

and then divide that by 56 ( atomic wt of Fe) ?

Answer 3

Fe = .33% * 67200

Answer 4

yeah you need to find the mass of iron in the hemoglobin molecule. yep thats it.

Answer 5

wait i misread the question. It's asking for the number of atoms in 1 Hb.

so you should divide the molecular mass of Hb by avogadros number first.

Answer 6

that means
221.76/56 = 4 moles :)

Thanks buddy!

Answer 7

which means 4 atoms per Hb

Answer 8

so that means it 4 Atoms per Hb.! not 4 moles!!!!

Answer 9

yes, thats why i said you had to divide the MW by avogadros number (to find the mass of 1 Hb molecule, not a whole mole).

Answer 10

Alright!
Thanks