What is the molar mass of Fe2O3? (with units)
The correct answer and explanation is:
Correct Answer:
The molar mass of Fe₂O₃ is 159.69 g/mol.
Explanation:
The molar mass (also called molecular weight) of a compound is the sum of the atomic masses of all atoms present in its chemical formula. To find the molar mass of Fe₂O₃ (iron(III) oxide), we need to identify the atomic masses of iron (Fe) and oxygen (O), then multiply by how many atoms of each are in the formula, and sum the results.
Step-by-step Calculation:
1. Determine the number of each type of atom:
- Fe₂O₃ means the compound has:
- 2 atoms of iron (Fe)
- 3 atoms of oxygen (O)
2. Use atomic masses from the periodic table:
- Atomic mass of iron (Fe) ≈ 55.85 g/mol
- Atomic mass of oxygen (O) ≈ 16.00 g/mol
3. Multiply and sum:
- Iron: 2 × 55.85 g/mol = 111.70 g/mol
- Oxygen: 3 × 16.00 g/mol = 48.00 g/mol
4. Add together to find total molar mass:
- Total molar mass = 111.70 + 48.00 = 159.70 g/mol
(Rounding rules may slightly vary depending on how many decimal places are used; some references list the total as 159.69 g/mol using more precise atomic masses.)
Why This Matters:
The molar mass is critical in stoichiometry—the area of chemistry that deals with the quantitative relationships between substances in chemical reactions. For instance, if a reaction requires 1 mole of Fe₂O₃, a chemist must weigh out 159.69 grams of it. Accurate molar mass calculations ensure that reactions are balanced properly and that the correct proportions of reactants and products are used or formed. This is vital in laboratory work, industrial chemistry, and pharmaceuticals, where precision is essential.