Empirical Formula

Empirical Formula in chemistry is defined as the simplest ratio of the elements present in the compound. It does not take into account that these elements are connected with each other in any manner. This is explained in the formula of Glucose as we know that the formula for Glucose is C₆H₁₂O₆ here we see that there are 3 atoms in the glucose molecule, they are carbon, hydrogen, and oxygen, Now the ratio of these elements is 1: 2: 1 i.e. for one molecule of hydrogen we have 2 molecules of hydrogen and one molecule of oxygen. So its empirical formula is CH₂O. It doesn’t tell us how many elements of each element are there in the Glucose molecule.

In this article, we will learn about the Empirical Formula in Chemistry, Molecular Formula, the Difference between Molecular Formula and Empirical Formula, and others in detail.

Empirical Formula

Empirical formula in Chemistry is the simplest formula for a compound. It is defined as the ratio of subscripts of the smallest possible whole number of the elements present in the formula. This formula gives information about the ratio of the number of atoms in the compound.

There is a relationship between molecular formula and empirical formula, which is given by,

Molecular Formula = n × Empirical Formula

where,

• n is Whole Number

To get a better understanding of the empirical formula, let’s look into an example,

Molecular formula of acetylene is C₂H₂

Emeperical Formula Definition

Empirical formula is the simplest ratio of number of each different atom present in the compound

Empirical Formula = Molecular Formula/n

For Example, C₂H₂ can be represented as 2(CH)

So, Empirical formula of Acetylene is CH

Molecular Formula

Molecular Formula of a compound is defined as the formula that tells us how may atoms are there in a molecule of the compound. It tells us exactly how many atoms are required to form a molecule. We know that molecular formula of water is H₂O. This signifies that in a water molecule we have two atoms of Hydrogen and an Oxygen atoms linked together to form a water molecule.

Molecular Formula Examples

Molecular Formula for various compounds are,

• Molecular Formula of Benzene: C₆H₆
• Molecular Formula of Ethyl Alcohol: C₂H₅OH
• Molecular Formula of Ethane: C₂H₆

Molecular Formula Vs Empirical Formula

The molecular formula and empirical formula of various compounds are different (in some special cases they can be same). They represent different properties of the compound. The differences between Empirical Formula and the Molecular Formula of the compound are given below in the table.

Empirical Formula	Molecular Formula
Empirical Formula represent the simplest ratio in which the atoms combined to form a molecule.	Molecular formula tells us that exactly how many atoms combined to form molecule.
Example: Empirical Formula for Butane is C2H5	Example: Molecular Formula for Butane is C4H10

Empirical Formula of Various Compounds

Emperical formula of any compound only tells us that how many atoms are in any compound and they are in which ratio. Empirical formula for some important compounds are discussed below.

Empirical Formula of C₆H₁₂O₆(Glucose)

• Empirical Formula of Glucose is CH₂O

Empirical Formula of Rust

• Empirical Formula of Rust i.e. Iron Oxide is Fe₂O₃

Empirical Formula of Benzene

• Empirical Formula of Benzene is CH

Empirical Formula of Urea

• Empirical Formula of Urea is CH₄N₂O

Empirical Formula of Acetic Acid

• Empirical Formula of Urea is CH₂O

Empirical formula for Magnesium Oxide

• Empirical Formula of Magnesium Oxide is MgO

How to Find Molecular Formula from Empirical Formula?

We can easily calculate the molecular formula from empirical formula by following the steps added below,

Step 1: Find molar mass of the Empirical Formula.

Step 2: Find the molecular mass of the given compound and divide the following molecular formula by the empirical formula from step 1.

Step 3: The whole number is obtained as a result of division. Multiply each atom of the empirical formula in subcript by this whole number.

This is the required molecular formula.

Read More,

• Molecular Weight
• Chemical Formula
• Chemical Formula of Common Compounds

Examples of Emperical Formula

Example 1: The Empirical formula of Butane is C₂H₅. Calculate the Molecular formula when the measured mass of the compound is 58.1224

Solution:

Atomic mass of given empirical formula = 2(C) + 5(H) = 2(12.011) + 5(1.00784) = 29.0612u

But, the measured molecular mass for Butane is given as 58.1224u

By using the expression, Molecular formula = n × empirical formula

n = weight of molecular formula/weight of empirical formula

= 58.1224/29.0612

= 2

Molecular formula = 2 × C₂H₅

= C₄H₁₀

Example 2: Find a molecular formula for the compound having the empirical formula CH₂ with a molecular weight of 42.08.

Solution:

Atomic mass of given empirical formula = C + 2(H) = 12.011 + 2(1.00784) = 14.02u

But, the measured molecular mass for given compound is 42.08u

By using the expression, Molecular formula = n × empirical formula

n = weight of molecular formula/weight of empirical formula

= 42.08/14.02

= 3

Molecular formula = 3 × CH₂

= C₃H₆

Example 3: Find the empirical for the compound with molecular formula C₆H₁₂O₆.

Solution:

C₆H₁₂O₆ = 6 × CH₂O

We know that Molecular Formula = n × Empirical Formula

Here, n = 6

So empirical formula for the given compound is CH₂O.

FAQs on Empirical Formula

1. Define Empirical Formula.

Empirical formula is defined as the formula of the molecules that tells us the simplest ratio of the the atoms present in the molecule. This is explained by the example as empirical formula of ethylene is CH. This tells us that in ethylene one molecule of carbon reacts with one molecule of hydrogen.

2. What is Molecular Formula?

Molecular formula of any chemical compounds tells us about the total atoms present in any molecule. This tells us that exactly how many molecules are required to form the given molecule. This is explained by the example that molecular formula of ethylene is C₂H₂. This tells us that in an ethylene molecule two carbon atoms combined with two hydrogen atoms to get a the ethylene molecule.

3. What is the Use of Empirical Formula?

Empirical formula is generally used to simply show what elements are present in a molecule. This is useful when one wants to know at a glance about what elements they are dealing with.

4. What is the Difference Between Molecular Formula and Empirical Formula?

Molecular Formula specifies the actual number of atoms of different elements in a compound. In the other side, Empirical Formula gives the simplest ratio of number of each different atom in a compound.

5. Determine Emperical Formula of An Oxide of Iron.

There are various types of Iron Oxide such as,

• Ferrous Oxide (FeO)
• Ferric Oxide (Fe₂O₃)

Emperical Formula of ferrous oxide is FeO.