Question

how 2 find relative molecular mass of haemoglobin? given that in a haemoglobin, there are 4 iron atoms and the % by mass of iron in haemoglobin is 0.33%.

Answer 1

So the molecular mass of iron is 55.85 g/mol. Multiply that by four because there are 4 iron atoms. Then multiply that number by 3, because iron makes up only a third of the weight of haemoglobin. You must multiply by 3 in order to account for the other 2/3 of the haemoglobin's weight. 670.2 g/mol

Answer 2

iron is a third of one percent, not a third. answer is 100x larger

Answer 3

Oh yes, sorry I didn't read properly that it is 0.33%, not 33%! Yes... so the answer is 670.2 *100 = 67020 g/mol

Answer 4

wait..i'm sorry..but i'm a little confused with the steps..after 55.85 x 4..then i supposed to times 3x100?

Answer 5

Yes. Because haemoglobin is not made up completely of iron, you must account for the mass of haemoglobin that is not iron! The mass of iron in haemoglobin (55.85*4) represents 0.33% of the total mass. Therefore to get from 0.33% to 100%, you can first multiply by 3 (to get from 0.33% to 1%), and then multiply by 100 (to get from 1% to 100%). Then you will have got the total mass of haemoglobin. Does this make sense?

Answer 6

oh ok...thanks a lot, i understand now..

Answer 7

No problem