What must the ratios of moles be expressed as when determining an empirical formula?

When determining an empirical formula, the ratios of moles must be expressed as whole numbers. This is because the empirical formula represents the simplest whole number ratio of the elements in a compound. For example, if the mole ratio of carbon to hydrogen in a compound is found to be 1:2, this reflects the simplest form of their ratio.

While calculations may initially yield decimal values or fractions, these must be converted to whole numbers to accurately reflect the composition of the compound. The process often involves multiplying all ratios by the same factor to eliminate any fractions and achieve whole numbers. This ensures that the resulting empirical formula correctly conveys the relative quantities of each element in the simplest terms.

Other options, such as decimal numbers, fractions, or percentages, do not provide the precise representation needed for an empirical formula, which is explicitly defined as a ratio of whole numbers.