When calculating the empirical formula, what is the first step?

To determine the empirical formula of a compound, the first step is to find the mass of each element present in the compound. This involves analyzing the composition of the compound, usually through experimentation or deriving mass percentages from a chemical formula. Once these masses are obtained, they can be used to calculate the number of moles of each element by converting the masses to moles using the atomic masses of the elements. This is crucial as the empirical formula is based on the simplest whole-number ratio of the moles of the elements in the compound.

The other choices do not contribute to finding the empirical formula. Knowing the molecular weight or the boiling point of a compound does not help in identifying the ratios of the constituent elements. Density is also not relevant in this context, as it does not indicate the composition of the elements within the compound. Therefore, finding the mass of each element is the essential and first step in deriving the empirical formula.