Iron (Fe) is one of the most abundant and significant elements in both chemistry and biology. It plays a vital role in industrial applications and is also a crucial component of biological systems, such as hemoglobin. Understanding the molecular mass of Fe is essential for students preparing for NEET, JEE, and other competitive exams. This article provides an in-depth explanation of the molecular mass of Fe, its calculation, and its importance in various scientific applications.
What is the Molecular Mass?
Molecular mass is defined as the sum of the atomic masses of all the atoms in a molecule. It is expressed in atomic mass units (amu) or unified mass units (u). However, for single elements like Fe, which commonly exist in their atomic form rather than as molecules, the term atomic mass is more appropriate. Yet, in general practice and exams, it is often referred to as molecular mass for uniformity.
Atomic Number and Symbol of Iron (Fe)
| Property | Value |
|---|---|
| Chemical Symbol | Fe |
| Atomic Number | 26 |
| Position in Periodic Table | Period 4, Group 8 |
| Classification | Transition Metal |
Iron is a transition metal and is widely used in metallurgy and biology due to its reactivity and bonding characteristics.
Molecular Mass of Fe
The atomic mass of iron (Fe) is approximately 55.845 u.
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This value is calculated as the weighted average of all the isotopes of iron found in nature.
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It is important to note that Fe usually exists in elemental or ionic form (Fe²⁺, Fe³⁺) and does not commonly form diatomic molecules like O₂ or H₂.
Hence, when asked for the molecular mass of Fe, it is understood as the atomic mass, which is 55.845 u.
How to Calculate the Molecular Mass of Iron Compounds
While Fe as an element has a single atomic mass, iron is often found in compounds. Here’s how you calculate the molecular mass in such cases:
Example 1: Molecular Mass of FeCl₃ (Iron(III) Chloride)
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Atomic mass of Fe = 55.845 u
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Atomic mass of Cl = 35.453 u
Molecular mass of FeCl₃ =
= 55.845 + (3 × 35.453)
= 55.845 + 106.359
= 162.204 u
Example 2: Molecular Mass of Fe₂O₃ (Iron(III) Oxide)
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Atomic mass of Fe = 55.845 u
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Atomic mass of O = 16.00 u
Molecular mass of Fe₂O₃ =
= (2 × 55.845) + (3 × 16.00)
= 111.69 + 48.00
= 159.69 u
Understanding such calculations is important for solving numerical problems in NEET and other entrance exams.
Importance of Knowing the Molecular Mass of Fe
1. In Stoichiometry
Molecular mass is crucial when calculating the amount of reactants and products in chemical reactions. It helps in determining moles and balancing equations efficiently.
2. Medical and Biological Use
Iron is a critical component of hemoglobin in blood. Accurate knowledge of its atomic mass is essential in fields such as biochemistry and pharmacology.
3. Industrial Applications
Iron is a key element in alloy production, including steel. Molecular mass helps in formulation, refining, and understanding physical properties.
4. NEET & JEE Exam Relevance
Numerous chemistry questions involve calculating the molecular mass of elements and compounds. Iron-based compounds are frequently used in such questions.
Key Information on Fe
| Property | Value |
|---|---|
| Chemical Name | Iron |
| Symbol | Fe |
| Atomic Number | 26 |
| Atomic Mass (Molecular Mass) | 55.845 u |
| Common Oxidation States | +2, +3 |
| Common Compounds | FeCl₃, Fe₂O₃, FeSO₄ |
Conclusion
The molecular mass of Fe (Iron) is 55.845 u, and this value plays a significant role in chemistry, biology, and industrial sciences. For students preparing for competitive exams like NEET 2025, understanding this concept thoroughly will help tackle questions related to atomic structure, stoichiometry, and chemical reactions. Mastering such foundational topics is the key to excelling in the chemistry section of any entrance exam.
Molecular Mass of Fe FAQs
Q1. What is the molecular mass of Fe?
Answer: The molecular mass (more accurately, atomic mass) of iron (Fe) is 55.845 unified atomic mass units (u). This value is a weighted average of the naturally occurring isotopes of iron.
Q2. How is the molecular mass of iron calculated in compounds?
Answer: To calculate the molecular mass of iron in a compound, add the atomic mass of Fe to the atomic masses of other elements in the compound.
For example, in FeCl₃:
Molecular mass = 55.845 (Fe) + 3 × 35.453 (Cl) = 162.204 u
Q3. Why is knowing the molecular mass of Fe important for NEET and JEE?
Answer: The molecular mass of Fe is essential for solving stoichiometric problems, balancing chemical equations, and determining molar relationships in reactions—all of which are frequently tested in NEET and JEE Chemistry sections.
Q4. Does iron (Fe) form diatomic molecules like oxygen (O₂)?
Answer: No, iron (Fe) does not exist as a diatomic molecule. It typically exists as a single atom in metallic form or forms ions and compounds (e.g., Fe²⁺, Fe³⁺, FeCl₃, Fe₂O₃).
Q5. What is the difference between atomic mass and molecular mass in the case of Fe?
Answer: Atomic mass refers to the mass of a single atom of Fe (55.845 u), while molecular mass is used when Fe is part of a compound (e.g., FeSO₄). Since elemental iron exists as single atoms and not as diatomic or polyatomic molecules, we usually refer to its atomic mass.
