🧪 Determining the Empirical Formula of a Compound
The empirical formula of a compound represents the simplest whole-number ratio of the elements present in the compound. Follow the steps below to determine it from experimental data.
🔢 Step 1: Convert Percentages to Mass
Assume you have 100 g of the compound. This way, the percentages become grams directly. For example, 40% becomes 40 g.
⚖️ Step 2: Convert Mass to Moles
Use the formula: moles = mass (g) ÷ molar mass (g/mol) for each element.
➗ Step 3: Divide by the Smallest Number of Moles
Divide all the mole values by the smallest number among them. This gives a mole ratio.
✖️ Step 4: Multiply to Get Whole Numbers
If the mole ratios are not whole numbers, multiply all values by the same factor to convert them into whole numbers (e.g., 1.5 × 2 = 3).
🧮 Step 5: Write the Empirical Formula
Use the whole number ratios as subscripts in the chemical formula.
📌 Example:
A compound contains 40% carbon, 6.7% hydrogen, and 53.3% oxygen.
- Assume 100 g: C = 40 g, H = 6.7 g, O = 53.3 g
- Moles: C = 40 ÷ 12 = 3.33, H = 6.7 ÷ 1 = 6.7, O = 53.3 ÷ 16 = 3.33
- Divide by smallest (3.33): C = 1, H = 2, O = 1
- Empirical Formula = CH2O
✅ By following this method, you can find the simplest ratio of elements in any compound using just mass or percentage data.