Question

Haemoglobin contains \(0.33 \%\) of iron by weight. The molecular weight of haemoglobin is approximately 67200 . The number of iron atom (at. wt of \(\mathrm{Fe}\) is 56 ) present in one molecule of haemoglobin are (a) 1 (b) 6 (c) 4 (d) 2

Short answer

The number of iron atoms per hemoglobin molecule is 4.

Step-by-step solution

Determine the Weight of Iron in One Molecule of Hemoglobin

First, calculate the weight of iron present in one molecule of hemoglobin using the percentage of iron by weight, which is given as 0.33%. The molecular weight of hemoglobin is 67200, so the weight of iron is \(\frac{0.33}{100} \times 67200 = 221.76\).

Calculate the Number of Moles of Iron in One Molecule

Next, use the atomic weight of iron to find the number of moles of iron in one molecule of hemoglobin. The atomic weight of iron is 56. Thus, the moles of iron are \(\frac{221.76}{56} \approx 3.96\).

Determine the Number of Iron Atoms in One Molecule

The number of moles of iron calculated in the previous step (approximately 3.96) would be very close to a whole number because each molecule typically contains whole atoms. Round 3.96 to the nearest whole number to find the number of iron atoms in one molecule of hemoglobin, which is 4.

Key concepts

Percentage Composition

Understanding the percentage composition of a compound is crucial in analyzing its molecular structure. In the context of haemoglobin, the given percentage indicates the proportion of an element—in this case, iron—relative to the total molecular weight. This concept is used to determine how much of a particular element exists per 100 parts of a compound.

For haemoglobin, the percentage composition of iron is given as 0.33%. This means that in every 100 units of haemoglobin, there are 0.33 units of iron. By knowing the total molecular weight of haemoglobin, which is 67200 units, we can calculate the actual weight of iron.

Here’s the straightforward formula used:

• Weight of element = (Percentage of element / 100) × Molecular weight of compound

By substituting the given values, we find that the weight of iron in one molecule of haemoglobin is 221.76 units.

Molecular Weight Calculation

Molecular weight represents the total mass of all atoms present in a molecule. For haemoglobin, this weight is approximately 67200 units, which is a summation of the atomic weights of all atoms within the molecule.

To calculate the portion of this weight contributed by iron, we use the concept of percentage composition. With iron accounting for 0.33% of the total weight, we multiply the molecular weight by this percentage, divided by 100.

This calculation provides the equivalent weight of iron in a single molecule of haemoglobin:

• Weight of iron (Fe) = (0.33 / 100) × 67200 = 221.76

Understanding the molecular weight allows us to break down intricate compounds like haemoglobin into quantifiable elements, aiding in further analysis such as counting atoms or determining specific molecular structures.

Iron Atom Count

Counting the exact number of iron atoms in a molecule involves a few calculation steps. First, we need to find out the weight of iron present in one molecule of the compound.

Using the weight calculated from the percentage composition, we identify the number of moles, which represents the amount of substance.

• Number of moles of iron = Weight of iron / Atomic weight of iron

Inserting the values:

• Number of moles of iron = 221.76 / 56 ≈ 3.96

Since each compound is made up of whole atoms, we assume close to whole numbers in practical scenarios. Thus, rounding 3.96 gives us 4. Therefore, there are 4 iron atoms present in one molecule of haemoglobin.

Understanding how to count atoms helps in comprehending how elements are structured in compounds, providing vital information needed in various chemical analyses and applications.