Empirical Formulas and Molecular Formulas

Earlier, chemical formulas were determined by the mass of elements that form a molecule but later, two important formulas were formulated- molecular formula and empirical formula.

The empirical formula is the simplest ratio of the number of atoms in the molecule, on the other hand the molecular formula is the number of individual atoms in that molecule. An empirical formula is the simplified version while a molecular formula is generally the multiple of the empirical formula.

One can summarize the relation between empirical and molecular formula as, 

Molecular Formula  = n x Empirical Formula

Where, n represents the ratio of molecular and empirical mass of the compound.

What is Molecular Formula?

• The molecular formula is derived from molecules and is representative of  the total number of individual atoms in a molecule of a compound.
• In a molecular formula a subscript is used to denote the number of atoms of each molecule in the compound.
• Molecular formulas are linked to the gram molecular masses that are multiples of the associated empirical formula mass.

How Do You Define Empirical Formula

• The empirical formula by definition, simply put, is the simplest form of a compound represented as the ratio of elements that is written in the lowest possible whole number of the subscripts. It is also called the simplest formula.
• Empirical formula of a compound is the lowest whole number of the number of atoms of the molecule. 
• The empirical formula provides information about in which ratio the atoms involved in the compound are related to each other. The percentage composition of each element in a compound is directly related to its empirical formula.

So we can summarize that,

• Empirical formula simply is a ratio of atoms of individual elements in the compound, represented by a whole number. 
• Molecular formula shows the definite number of atoms of each element involved to form that particular molecule present in a compound. 

Empirical Formula Vs Molecular Formula

The Difference 

The significant difference between the empirical and molecular formula is that the former represents a simplest ratio of atoms while the latter shows the total number of atoms, in any compound. 

An empirical formula also represents the percentage of a particular element in that compound. 

Example

The molecular formula of water is H2O.

The empirical formula here is in the ratio of  2:1. For 2 Hydrogen atoms, there is one oxygen atom. 

In this case, both the empirical and molecular formula remain the same.

Lets see other examples, 

The similarities 

• The elements that form the compound are represented in both formulas.
• Both the formulas represent the ratio of atoms but the empirical formula is in the simplest form. Molecular formula will be its multiple.

How to Find the Empirical Formula of a Compound?

The simplest way to determine the empirical formula of any compound is to find the simplest ratio of atoms in a given compound.

The simple steps to help in determining the empirical formula of any compound are, 

• Finding the mass of all the elements.
• Use each element’s molar mass to convert the grams of each element to moles.
• Determine its simplest ratio.

What is the Use of Empirical Formula?

Empirical formulas use the lowest notational form that provides the lowest ratio of numbers between the elements in a compound. Unlike molecular formula, it may not impart other vital information regarding the number of atoms present in that particular molecule.

The empirical formula is a kind of chemical formula that shows the ratio of atoms involved in the chemical formula.  The relation between the empirical and molecular formula is represented as Molecular Formula  = n × Empirical Formula. It is useful in finding both the empirical and molecular formula of any compound. The empirical formula is significant in experimental chemistry; where it lets the statisticians find the probable result when sufficient data is not available.