Empirical and Molecular Formulas

Front

What is an empirical formula?

Back

An empirical formula represents the simplest whole-number ratio of atoms of each element in a compound.

Front

What is a molecular formula?

Back

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

Front

How do you determine the empirical formula from percent composition?

Back

Convert the percentages to grams, then to moles, and simplify the mole ratio to the smallest whole numbers.

Front

What is the empirical formula of a compound with 81.82% carbon and 18.18% hydrogen?

Back

C3H8

Front

How do you calculate the molar mass of a compound?

Back

Add the atomic masses of all the atoms in the molecular formula.

Front

What is the molar mass of C4H6?

Back

4(12.0111) + 6(1.00794) = 54.0944 g/mol.

Front

What is the empirical formula of Si2F6?

Back

SiF3

Front

What is the empirical formula of K2SO4?

Back

K2SO4

Front

If the empirical formula is CH2O and the molar mass is 180 g/mol, what is the molecular formula?

Back

C6H12O6

Front

How do you convert an empirical formula to a molecular formula?

Back

Determine the molar mass of the empirical formula, divide the compound's molar mass by this value, and multiply the subscripts in the empirical formula by this ratio.