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NEET CHEMISTRYMedium

0.33% of iron (by weight) is present in hemoglobin (Molecular wt = 67200). The number of iron atom(s) in one molecule will be:

A

1

B

2

C

3

D

4

Step-by-Step Solution

  1. Identify the Principle: The mass percentage (w/ww/w) of a component in a solution (or compound) is defined as the mass of the component divided by the total mass multiplied by 100 [Class 12 Chemistry, Ch 1, Sec 1.2.1, Eq 1.1].
  2. Calculate Mass of Iron: Mass of Iron=Percentage×Molecular Weight100\text{Mass of Iron} = \frac{\text{Percentage} \times \text{Molecular Weight}}{100} Mass of Iron=0.33×67200100=221.76 u\text{Mass of Iron} = \frac{0.33 \times 67200}{100} = 221.76 \text{ u}
  3. Determine Number of Atoms: The atomic mass of Iron (Fe) is approximately 56 u56 \text{ u} (standard data). Number of atoms=Total Mass of IronAtomic Mass of Fe\text{Number of atoms} = \frac{\text{Total Mass of Iron}}{\text{Atomic Mass of Fe}} n=221.7656≈3.96n = \frac{221.76}{56} \approx 3.96 Rounding to the nearest whole number, there are 4 iron atoms per hemoglobin molecule.
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