Percent Composition, Empirical & Molecular Formulas

Front

What is percent composition?

Back

Percent composition is the percentage by mass of each element in a compound.

Front

How do you calculate the empirical formula from percent composition?

Back

1. Convert the percentages to grams. 2. Convert grams to moles using molar mass. 3. Divide by the smallest number of moles to find the simplest ratio.

Front

What is the empirical formula of a compound?

Back

The empirical formula is the simplest whole-number ratio of the elements in a compound.

Front

What is the molecular formula?

Back

The molecular formula shows the actual number of atoms of each element in a molecule of the compound.

Front

How do you determine the molecular formula from the empirical formula?

Back

Multiply the empirical formula by a whole number (n) that gives the molecular weight of the compound.

Front

What is the molar mass of sulfur (S)?

Back

32.07 g/mol

Front

What is the molar mass of oxygen (O)?

Back

16.00 g/mol

Front

If a compound is 40.05% S and 59.95% O, what is the empirical formula?

Back

SO3 (Sulfur trioxide)