Molecular Formula Acetic Acid Glucose Formaldehyde

Steps Find the empirical formula Calculate the molar mass of the empirical formula Multiplier = ( 𝑚𝑜𝑙𝑎𝑟 𝑚𝑎𝑠𝑠 𝑔𝑖𝑣𝑒𝑛 𝑚𝑜𝑙𝑎𝑟 𝑚𝑎𝑠𝑠 𝑜𝑓 𝑒𝑚𝑝𝑖𝑟𝑖𝑐𝑎𝑙 𝑓𝑜𝑟𝑚𝑢𝑙𝑎 ) Multiply empirical formula subscripts by the multiplier to get the molecular formula

Example 1 A compound composed of 40.68% carbon, 5.08% hydrogen and 54.24% oxygen has a molar mass of 118.1 g/mol. Determine the empirical and molecular formula. E.F. = C2H3O2 40.68 g C 1 mol C 12.01 g C = 3.387 mol C 3.387 = 1.00 mol C ×2 = 2 Molar Mass: C: 12.01 ×2 H: 1.01 ×3 + O: 16.00 ×2 59.05g 5.08 g H 1 mol H 1.01 g H = 5.03 mol H 3.387 = 1.49 mol H ≈ 1.5 ×2 = 3 118.1 g 59.05g 54.24 g O 1 mol O 16.00 g O = 3.390 mol O 3.387 = 1.00 mol O ×2 = 2 = 2 M.F. = C4H6O4

Example 2 A compound has a molar mass of 462.8 g/mol and contains 77.87% C, 11.76% H, and 10.37% O. Determine the empirical and molecular formulas. M.F. = C30H54O3