Molar Mass and Molecular Mass

Do you know the difference between molar mass and molecular mass? If not, don’t worry! In this article, we will discuss the differences between these two terms. Molar mass is a measure of the weight of a molecule, while molecular mass is a measure of the weight of an atom. It’s important to understand the differences between these two terms, as they are often confused. Let’s get started!

What is Molar Mass? 

Molar mass is the weight of a mole of atoms or molecules. A mole is defined as the amount of substance that contains as many atoms, molecules, or ions as there are in 12 grams of carbon-12. Molar mass can be expressed in grams per mole (g/mol) or kilograms per mole (kg/mol).

What is Molecular Mass? 

It’s the total of all the atoms in a molecule’s average atomic masses. The molecular mass of a molecule is usually expressed in Daltons (abbreviated Da or u). One Dalton is defined as one-twelfth the mass of an atom of carbon-12. This unit is also called an atomic mass unit (amu). Molecular mass can be thought of as the weight of a molecule.

Molar Mass and Molecular Mass: Difference 

Let’s compare and contrast the definitions of molar mass and molecular mass now that we know what they mean.

Meaning

The main difference between molecular mass and molar mass is that molar mass is the weight of a mole of atoms or molecules, while molecular mass is the total of all the atoms in a molecule’s average atomic masses.

Units

Molar mass is measured in grams per mole (g/mol), whereas molecular mass is measured in Daltons (abbreviated Da or u).

Scale

Molar mass is measured on a larger scale than molecular mass because it measures the weight of a mole of atoms or molecules. Molecular mass is measured on a smaller scale because it only measures the weight of an individual atom or molecule.

Precision

Molar mass is more precise than molecular mass because it uses average atomic masses to calculate the total weight of a molecule. Molecular mass can be less precise if there is significant variation in the atomic masses of different atoms in a molecule.

Application 

The number of particles that has a specific number of moles is calculated using molar mass. Molecular mass is used to identify the unknown chemicals and to figure out what a compound’s formula is.

Examples

Let’s consider two examples to illustrate the differences between molar mass and molecular mass.

First, let’s calculate the molar mass of water. We know that the atomic weight of hydrogen is approximately 0.007 amu, and the atomic weight of oxygen is approximately 0.0094 amu. So, the molar mass of water would be:

(0.007 amu x (12 grams/mol)) + (0.0094 amu x (12 grams/mol)) = 0.018 grams/mol

Now, let’s calculate the molecular mass of water. We know that the formula for water is H₂O, which means that there are two atoms of hydrogen and one atom of oxygen in each molecule of water. So, the molecular mass of water would be:

(0.007 amu x (12 grams/mol)) + (0.0094 amu x (12 grams/mol)) = 0.0308 grams/mol

Conclusion

To understand the difference between molar mass and molecular mass, it is important to first know what each term means. Molar mass is a measure of the average atomic weight of a molecule, while molecular mass is the total of all the atoms in a molecule. By understanding these concepts, you can more accurately calculate the weight and concentration of molecules in solutions.