To calculate the empirical formula from element percentages, divide the percentage of each element by its respective atomic mass (Ar). This process yields the number of moles for each element, which can then be simplified to the smallest whole number ratio. For example, if you have 40% carbon (C), 6.7% hydrogen (H), and 53.3% oxygen (O), you would divide each percentage by the atomic masses of C (12), H (1), and O (16) respectively to find the empirical formula.
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