Molecular Formula Calculator

Molecular Formula Calculator

This molecular formula calculator calculates the molecular formula of any compound based on its empirical formula and molar mass. It can handle formulas for both organic and inorganic compounds.

Molecular Formula:

A chemical formula that gives the total number of atoms of each element present in a molecule of a compound using the symbol & subscripts is called the molecular formula.

Subscripts are small numbers that are written after the element symbol and indicate the exact number of atoms present in the molecule of a compound. A subscript can be a whole number zero or greater than one. For example, CO2 for carbon dioxide (one carbon atom and two oxygen atoms).

The following table shows the molecular formula of various compounds:

How To Calculate Molecular Formula?

Finding the molecular formula of a compound involves four steps:

Step #1: Get The Required Information

• The empirical formula of the compound
• The molar mass of the compound. It is typically expressed in grams per mole (g/mol)

Step #2: Calculate The Empirical Formula Mass(EFM)

• See the atomic masses of each element on the periodic table
• Multiply the number of atoms of every element by the atomic mass of each element
• Add the masses of all the elements together. It will give you the EFM

Step #3: Determine The Multiplier (n)

• Divide the molar mass of the compound by the empirical formula mass

Note: The value of n is considered as a whole number and not any decimal number. 

Step #4: Multiply The Empirical Formula By The Multiplier (n)

• Once you have the multiplier (n), multiply each subscript in the formula by n. It will give you the molecular formula

Molecular Formula = n(Empirical Formula)

Example: 

Suppose you have a compound of boron and hydrogen is BH4. Its molar mass is 31.2 g/mol. Now find the molecular formula.

Solution:

EFM = 10.811+1.008+1.008+1.008+1.008 =14.843g/mol

Now we have to find the value of n as follows:

n = MM(Molar Mass) EFM(Empirical Formula Molar Mass)

n = 31.2 14.843

By putting values in the molecular formula equation:

Molecular Formula =2 * (BH4)

Molecular Formula = B2H8

The molecular formula can be automatically determined with the use of our molecular formula calculator, where you just need to make a couple of clicks!

FAQ’s:

What Is The Rule of Molecular Formula?

• Single Atom: When there is only one atom of an element available in a molecule, then no number (subscript) is written after the element’s symbol(e.g., H for Hydrogen)
• Multiple Atoms: When there are two or more atoms of an element present, then the number (subscript) is written after the symbol of the element. It informs you about the number of atoms of each element present in the molecule (e.g., H2O for water, There are two Hydrogen atoms present)

What Are Compounds With The Same Molecular Formula But Different Arrangements of Atoms?

Isomers are compounds that share the same molecular formula (same number and type of atoms) but different structures of atoms. Because of this difference, these isomers have distinct physical and chemical properties. 

References:

From the source of Wikipedia: Chemical Formula.

From the source of chem.libretexts.org: Calculating Molecular Formulas for Compounds.