Final answer:
To find the empirical formula, convert percentage to grams, grams to moles, divide by the smallest mole value, and adjust to whole numbers. Multiply subscripts by the whole number found when dividing the compound's molar mass by the empirical formula mass to get the molecular formula.
Step-by-step explanation:
The Dulong and Petit rule is not directly used for determining the empirical formula of a compound. However, once you have an empirical formula, you can find the molecular formula if you have the molar mass of the compound. Here are the steps you can use to determine the empirical formula and then the molecular formula:
- Assume a 100 g sample of the compound so that percentages can be directly converted into grams.
- Convert the grams of each element to moles using their molar mass.
- Find a whole-number ratio by dividing the moles of each element by the smallest number of moles calculated.
- If necessary, multiply all moles by the smallest whole number to convert them to whole numbers to get the empirical formula.
- Calculate the empirical formula mass (EFM).
- Divide the molar mass of the compound by the empirical formula mass. The result should be a whole number or very close to one.
- Multiply all the subscripts in the empirical formula by this whole number to get the molecular formula.