The formula weight of Iron (III) carbonate, Fe2(CO3)3 is
a. 243.73
b. 291.73
c 115.85
d, 195 70
e. 515.10
The correct answer and explanation is :
The correct formula weight of Iron (III) carbonate, Fe₂(CO₃)₃, is 291.73 g/mol. So, the correct answer is:
b. 291.73
Explanation
The formula weight (also called molecular weight or molar mass) is the sum of the atomic masses of all the atoms in a chemical formula. Let’s calculate the formula weight of Fe₂(CO₃)₃ step by step.
Step 1: Identify the Atomic Masses
From the periodic table, the atomic masses are:
- Iron (Fe): 55.85 g/mol
- Carbon (C): 12.01 g/mol
- Oxygen (O): 16.00 g/mol
Step 2: Multiply by the Number of Atoms
The molecular formula Fe₂(CO₃)₃ contains:
- 2 Iron (Fe) atoms → 2 × 55.85 = 111.70 g/mol
- 3 Carbon (C) atoms → 3 × 12.01 = 36.03 g/mol
- 9 Oxygen (O) atoms → 9 × 16.00 = 144.00 g/mol
Step 3: Sum the Values
Now, add up all the contributions:
[
111.70 + 36.03 + 144.00 = 291.73 \text{ g/mol}
]
Thus, the formula weight of Fe₂(CO₃)₃ is 291.73 g/mol.
Why is this Important?
- The formula weight is crucial in stoichiometry, where it helps in converting between grams and moles.
- It is used in chemical reactions to determine reactant-product relationships.
- It is necessary in solution preparation, especially in industries and laboratories.
Common Mistakes to Avoid
- Forgetting to multiply the atomic masses by the number of atoms.
- Miscounting the number of oxygen atoms (since each carbonate group (CO₃) has 3 oxygens, and there are 3 carbonate groups).
Thus, the correct answer remains 291.73 g/mol (option b).