Balanced: Fe2O3 + 3CO → 2Fe + 3CO2
- Moles of Fe2O3 = 100 g ÷ 159.687 g/mol =
0.6262 mol - Divide by its coefficient (1) to get the reaction extent:
0.6262 mol - Multiply the extent by each coefficient for moles, then by molar mass for grams:
| Substance | Role | Coeff. | Moles | Mass |
|---|---|---|---|---|
| Fe2O3given | used | 1 | 0.6262 mol | 100 g |
| CO | used | 3 | 1.879 mol | 52.62 g |
| Fe | formed | 2 | 1.252 mol | 69.94 g |
| CO2 | formed | 3 | 1.879 mol | 82.68 g |
This assumes the given substance reacts (or forms) completely and everything else is in the right amounts. With two known reactant amounts, use the limiting reagent calculator.
How it works
The equation is balanced with exact arithmetic, and molar masses come from IUPAC standard atomic weights. The known amount is converted to moles, divided by its coefficient to give the "reaction extent", and multiplied by each coefficient to give the moles of every species — then by molar mass to give grams.
This assumes the known substance reacts (or forms) completely and that everything else is available in the right amounts. For real mixtures where one reactant runs out first, use the limiting reagent calculator; for the actual yield, apply a percent yield.
Frequently asked questions
- How do I do a mass-to-mass stoichiometry problem?
- Grams of A → moles of A (divide by molar mass) → moles of B (multiply by the mole ratio from the balanced equation) → grams of B (multiply by molar mass).
- How much iron can 100 g of Fe₂O₃ make?
- Fe₂O₃ + 3CO → 2Fe + 3CO₂. 100 g ÷ 159.69 g/mol = 0.6262 mol, which makes 2 × 0.6262 = 1.252 mol of iron, or about 69.9 g.
- Do I need to balance the equation first?
- No — the calculator balances it. Just type the formulas with an arrow, such as Al + O2 -> Al2O3.
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