Created By : Rina Nayak

Reviewed By : Rajashekhar Valipishetty

Last Updated : Apr 29, 2023


The chemical symbols that make up a molecular formula. It also includes the constituent elements as well as numeric subscripts that describe the number of atoms present in each element. It's a method of displaying chemical proportions data.

What does Molecular Weight mean?

The molecular weight is used in chemistry to calculate stoichiometry in chemical reactions. The relative molecular mass is the same as the molecular weight. The molecular weight is the total atomic weight of the atoms in a molecule. It refers to a molecule's mass.

Mass spectrometry, static light scattering, and the hydrodynamic method are all methods for calculating a molecule's molecular weight. M.W. is the abbreviation for molecular weight.


Molecular Formula

MOlecular Formula = n (Empirical formula). It specifies the atom type and the number of each element in the molecular compound. The formula will always be a multiple of the formula in integers. During the formation of a compound, it is the sole whole-integer ratio of atoms. A compound's formula is frequently an equivalent or a multiple of the compound's formula.

Molecular formulas are short and easy to express, but they lack the knowledge about bonding and atomic organization that a molecular formula provides. We express the number of atoms of each element present in each molecule as a subscript after that element's symbol since we represent the constituent elements by their chemical symbols.

A single line of element symbols and numbers is used. Other representations, such as parentheses, dashes, brackets, plus (+) and minus (–) signs, are sometimes included.

Properties of Molecules

Molecules with several functional groups that are interchangeable can also be expressed by surrounding the repeating group in round brackets. For example,  Isobutane can be written (CH3)3CH. Three lines (HCCH) or three pairs of dots (HC:::CH) can be used to depict a triple bond, and if there is any uncertainty, a single line or pair of dots can be used to denote a single bond.

Law of Composition

For example, in a 2:1 ratio, any water molecule is composed of two hydrogen atoms and one oxygen atom. When we look at the relative masses of oxygen and hydrogen during the formation of a water molecule, we can observe that oxygen makes up 94% of the total mass. As a result, the mass of hydrogen accounts for the remaining 6%. As a result, any water molecule will have the same mass proportion as this mass proportion.

How to Calculate Molecular Formula?

  • Step 1: Firstly calculate the molar mass formula. 
  • Step 2: Divide the compound's molar mass by the formula molar mass. The result should be a whole number or a close approximation of a whole number. 
  • Step 3: Finally, multiply the entire value by all of the subscripts within the formula. The formula is the end outcome.

FAQs on Molecular Formula

1. What's the easiest way to find out the molecular formula from the empirical formula?

We take the subscripts of the molecular formula (C6H12O6) and reduce them to the simplest whole-number ratios to derive the empirical formula of a known chemical, such as glucose. C1H2O1 is obtained by dividing this by 6.


2. Is the molecular formula the same as the real thing?

The kind and amount of atoms of each element contained in a molecular composition are determined by molecular formulae. In many circumstances, the molecular formula and the empirical formula are identical. Methane has a chemical formula of CH4 and an empirical formula of CH4 because it only has one carbon atom.


3. Is molecular mass the same as molar mass?

Furthermore, the fundamental distinction between the two is that molar mass refers to the mass of a mole of a certain substance. The mass of a molecule of a given chemical is known as molecular weight. The molar mass and molecular weight have distinct definitions and units, but the value is the same.