1. Assume a 100g Sample
* This makes the calculations easier. If the compound is 56.35% phosphorus, then it's also 56.35 g of phosphorus in a 100g sample.
* The remaining percentage (100% - 56.35% = 43.65%) is oxygen, or 43.65 g of oxygen in the sample.
2. Convert Grams to Moles
* Use the molar mass of each element to convert grams to moles:
* Phosphorus (P): 56.35 g / 30.97 g/mol ≈ 1.82 mol
* Oxygen (O): 43.65 g / 16.00 g/mol ≈ 2.73 mol
3. Find the Simplest Mole Ratio
* Divide each mole value by the smallest mole value:
* Phosphorus: 1.82 mol / 1.82 mol ≈ 1
* Oxygen: 2.73 mol / 1.82 mol ≈ 1.5
4. Adjust to Whole Numbers
* Since we have a 1.5 ratio for oxygen, multiply both ratios by 2 to get whole numbers:
* Phosphorus: 1 * 2 = 2
* Oxygen: 1.5 * 2 = 3
5. Write the Empirical Formula
* The empirical formula represents the simplest whole-number ratio of atoms in the compound.
* The empirical formula is P₂O₃.
