Question

If one molecule of hemoglobin contains 4 iron atoms, and they constitute `0.335%` by mass of hemoglobin, what is the molar mass of hemoglobin?

Answer 1

`66686.57gmol^-1`, rounded to two decimal places.

Explanation:

Let molecular mass of heamoglobin molecule be `=M`

One molecule of heamoglobin contains `4"Fe"` atoms of atomic mass

`=55.85" each"`,

Total mass of iron in one molecule of heamoglobin

`=4xx55.85=223.4`

To calculate the percentage of iron:

`M` amu of heamoglobin has iron`=223.4`

`100` amu of heamoglobin has iron`=223.4/Mxx100`

Equating to the given value,

`223.4/Mxx100=0.335`

Solving for `M`,

`M=223.4/0.335xx100`

`=66686.57gmol^-1`, rounded to two decimal places.
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At some places the iron percentage in heomoglobin is given as `0.3335%`. Using the published average atomic mass of iron as `55.847`,

`M=66982.9085gmol^-1`