Accepted answer
Answer included
The name iron(III) oxide indicates a binary ionic compound made of iron cations with a +3 charge and oxide anions with a −2 charge. The task is to choose subscripts that make the total charge zero.
Result: Fe2O3 (often called ferric oxide).
1) Translate the name into ion charges
| Part of the name | Meaning | Ion formed |
|---|---|---|
| iron(III) | Iron has oxidation state +3 (Roman numeral III means +3 for the metal cation) | Fe3+ |
| oxide | Oxygen as a monatomic anion has charge −2 | O2− |
2) Balance charges to make a neutral compound
- Identify charges: Fe3+ contributes \(+3\) each, and O2− contributes \(−2\) each.
- Find a common total charge magnitude so positives and negatives can cancel. The least common multiple of 3 and 2 is 6.
- Choose ion counts to reach \(+6\) and \(−6\): \[ 2 \times (+3) = +6 \quad \text{and} \quad 3 \times (-2) = -6. \]
- Write subscripts from the ion counts: 2 iron ions and 3 oxide ions gives Fe2O3.
3) Quick verification using oxidation states
A neutral formula must satisfy total charge \(= 0\). For Fe2O3:
\[ 2(+3) + 3(-2) = +6 - 6 = 0. \]4) Visualization: charge-neutrality ratio for iron(III) oxide
5) Common comparison (to avoid confusion)
| Compound name | Formula | Iron oxidation state(s) |
|---|---|---|
| iron(II) oxide | FeO | +2 |
| iron(III) oxide | Fe2O3 | +3 |
| iron(II,III) oxide | Fe3O4 | mixture of +2 and +3 |
The correct formula for iron(III) oxide follows directly from ion charges: Fe3+ and O2− must combine in the smallest whole-number ratio that makes total charge zero, giving Fe2O3.
Vote on the accepted answer
Upvotes: 0
Downvotes: 0
Score: 0