Final answer:
The empirical formula of a compound is calculated by assuming a 100 g sample for direct conversion of percent to grams, converting these to moles, finding the simplest whole number ratio of these moles, adjusting non-whole number moles by multiplication, and then composing the formula using these ratios.
Step-by-step explanation:
To calculate the empirical formula for a stimulant from its elemental percent composition, you can use the following steps:
Assume a 100 g sample of the compound to convert the percentage composition into grams directly.
Use the molar mass of each element to convert the grams to moles.
Divide the moles of each element by the smallest number of moles obtained from step 2 to find the simplest whole number ratio.
If not all moles are whole numbers, multiply by the smallest whole number to make them whole numbers for establishing the empirical formula.
Write the empirical formula by using the moles as subscripts.
To determine the percent composition, divide the mass of each element in one mole of the compound by the molar mass of the compound, and multiply by 100%.
Finally, the empirical formula mass (EFM) is the sum of the masses of all the elements represented in the empirical formula, which can be compared to the molar mass to find the molecular formula.