How can one derive the molecular formula from the empirical formula?

The molecular formula can be derived from the empirical formula by multiplying the empirical formula by a whole number.

The empirical formula of a compound provides the simplest whole-number ratio of the atoms of each element present. However, it does not provide the actual number of atoms in each molecule. To derive the molecular formula from the empirical formula, you need to know the molar mass of the compound.

First, calculate the molar mass of the empirical formula. This can be done by adding up the atomic masses of all the atoms in the empirical formula. The atomic masses can be found on the periodic table.

Next, divide the molar mass of the compound by the molar mass of the empirical formula. This will give you a whole number, or very close to a whole number. This number represents the number of empirical formula units in each molecule of the compound.

Finally, multiply the subscripts in the empirical formula by this number to get the molecular formula.

For example, let's say the empirical formula of a compound is CH and the molar mass of the compound is 26 g/mol. The molar mass of CH is approximately 13 g/mol. Dividing 26 g/mol by 13 g/mol gives 2. Therefore, the molecular formula of the compound is C2H2.

Remember, the molecular formula of a compound can be the same as its empirical formula, or it can be a multiple of the empirical formula. The key is to find that multiple, which requires knowing the molar mass of the compound.