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Obtaining an Empirical Formula from Experimental Data
- Write down (or calculate) as given the masses of each element present in a sample of the compound. If you are given mass percent composition, assume a 100-g sample and calculate the masses of each element from the given percentages.
- Convert each of the masses in Step 1 to moles by using the appropriate molar mass for each element as a conversion factor.
- Write down a pseudo-formula for the compound, using the moles of each element (from Step 2) as subscripts.
- Divide all the subscripts in the formula by the smallest subscript.
- If the subscripts are not whole numbers, multiply all the subscripts by a small whole number (see the following table) to arrive at whole-number subscripts.