To find the empirical formula of a compound, we follow these steps:

Here's how to determine the formula of the hydrated salt. To find the empirical formula of a compound, we follow these steps: 1. Assume a 100 g sample, so the percentages become masses in grams. 2. Convert the mass of each element and water to moles using their respective molar masses. 3. Divide the moles of each component by the smallest number of moles to find the simplest whole-number ratio. 4. Write the formula based on these ratios. Given percentages by mass: Iron (Fe) = 20.2% Sulphur (S) = 11.5% Oxygen (O) = 23.0% Water (H_2O) = 45.3% Given relative atomic masses: Fe = 56 S = 32 O = 16 H = 1 Step 1: Assume a 100 g sample. Mass of Fe = 20.2 g Mass of S = 11.5 g Mass of O = 23.0 g Mass of H_2O = 45.3 g Step 2: Calculate the moles of each component. Molar mass of Fe = 56 g/mol Molar mass of S = 32 g/mol Molar mass of O = 16 g/mol Molar mass of H_2O = (2 × 1) + 16 = 18 g/mol Moles of Fe = 20.2 g56 g/mol = 0.3607 mol Moles of S = 11.5 g32 g/mol = 0.3594 mol Moles of O = 23.0 g16 g/mol = 1.4375 mol Moles of H_2O = 45.3 g18 g/mol = 2.5167 mol Step 3: Divide by the smallest number of moles to find the simplest ratio. The smallest number of moles among Fe, S, and O is approximately 0.36. We will use the moles of S (0.3594 mol) as the smallest for the anhydrous part. Ratio for Fe: (0.3607)/(0.3594) ≈ 1.00 Ratio for S: (0.3594)/(0.3594) = 1.00 Ratio for O: (1.4375)/(0.3594) ≈ 4.00 This gives the anhydrous part of the formula as FeSO_4. Now, we find the ratio of water molecules to the anhydrous salt. We use the moles of FeSO_4 (which is 0.3594 mol, based on the 1:1 ratio of Fe and S). Ratio for H_2O: (2.5167)/(0.3594) ≈ 7.00 Step 4: Write the formula of the hydrated salt. The ratio of FeSO_4 to H_2O is 1:7. The formula of the hydrated salt is FeSO_4 · 7H_2O. 3 done, 2 left today. You're making progress.