Search the World of Chemistry

×

# Molar Mass Constant

26th Jun 2019 @ 2 min read

Physical Chemistry

The molar mass constant is a quantity similar to the atomic mass constant. The constant, as from the name, is related to the molar mass of carbon-12.

## Definition of Molar Mass Constant

It is defined as the one-twelfth of the molar mass of carbon-12.

## Symbol

The molar mass constant is denoted by Mu.

## Unit

The unit of the molar mass constant is g mol−1.

## Formula

According to the above definition, the formula of the constant is as follows: where 12C is the molar mass of carbon-12.

## Value of Molar Mass Constant

The approximate value of Mu is 1 g mol−1. The more precise value, as per Committee on Data for Science and Technology (CODATA), is given below. As we can see the above-mentioned value is very close to one. Thus, we can say for practical purposes Mu ≈ 1.

## Molar Mass Constant, Atomic Mass Constant, and Avogadro Constant

The molar mass constant, as mention earlier, is given as: Here, M(12C) is the molar mass of carbon-12, or in other words, the mass of carbon-12 in one mole.

The molar mass of carbon-12 can be expressed as the mass of one carbon-12 atom (m(12C)) multiplied by the Avogadro’s constant (NA). Using the above two equations , we get, From the definition of the unified mass unit (u) and the atomic mass constant (mu), we have the below relationship. From the above two equations, we have  Using Mu ≈ 1 g mol−1, ## Relation with Relative Atomic Weight

Relative atomic weight is a dimensionless quantity and it is denoted as Ar. The relative atomic weight of carbon-12 is 12. We can replace the numeral 12 in the equation Mu = 112 M(12C) by Ar(12C). Thus, we have From the above equation, the molar mass constant is the ratio of the molar mass of carbon-12 to the relative atomic weight of carbon-12.

## Associated Articles

If you appreciate our work, consider supporting us on ❤️ patreon.

Copy Article Cite 