Determining Empirical Formula from Molecular Formula
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Determining a compound's empirical formula from its molecular formula means dividing every subscript by the largest whole number that divides all of them evenly.
Acetic acid's molecular formula, C2H4O2, has subscripts 2, 4, and 2. The largest number dividing all three evenly is 2, giving a reduced ratio of 1, 2, 1 — the empirical formula CH2O. Glucose's molecular formula, C6H12O6, divides by 6 the same way, giving the identical empirical formula CH2O, even though glucose and acetic acid are different-sized molecules. Hydrogen peroxide, H2O2, divides by 2 as well, reducing to HO, a formula whose subscripts are already the smallest possible whole numbers.
Stopping after dividing only one subscript, instead of every subscript by the same number, produces a ratio that no longer matches the original molecule's actual atom counts.
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