Formulas of Compounds
- To understand the meaning of empirical formulas of compounds.
- Empirical formulas express the smallest whole-number ratio of atoms present in a compound; also called the simplest formula.
- Molecular formulas give the composition of the molecules that are present.
Calculation of Empirical Formulas
- To learn to calculate empirical formulas.
- Keep an eye on significant figures.
- Steps for Determining the Empirical Formula of a Compound:
- Obtain the mass of each element present (in grams).
- Determine the number of moles of each type of atom present.
- Divide the number of moles of each element by the smallest number of moles to convert the smallest number to 1. If all the numbers so obtained are integers (whole numbers), these are the subscripts in the empirical formula. If one or more of these numbers are not integers, go on to Step 4.
- Multiply the numbers you derived in Step 3 by the smallest integer that will convert all of them to whole numbers. This set of whole numbers represents the subscripts in the empirical formula.
- Percent by mass for a given element means the grams of that element in 100 g of the compound.
Calculation of Molecular Formulas
- To learn to calculate the molecular formula of a compound, given its empirical formula and molar mass.
Filed under: Chemistry Help , Chemistry, Empirical Formulas, Formulas of Compounds, Molecular Formulas
