# Molar Mass – concepts and formula

Last updated on October 30th, 2021 at 05:05 am

*The mass of one mole of a substance in grams is called its molar mass. The molar mass in grams is numerically equal to atomic/molecular/formula mass in u.*

The molar mass of water = 18.02 g mol^{-1}

The molar mass of sodium chloride = 58.5 g mol^{-1}

Molar mass is the mass of a single mole. In other words, Molar mass is the mass of a given substance divided by the number of moles.

Hence we can write that, **Molar mass (M) = Mass of substances (m ) / number of moles (n)=> M= m/n**

## Calculating molar mass from atomic mass

Here we will see how to calculate the molar mass of an element and a compound with some examples.

### how to calculate the molar mass of an element? | molar mass of titanium

The characteristic molar mass of an element is numerically equal to the atomic mass with a unit g/mol.

For example, the atomic mass of titanium is 47.88 u. So, the *molar mass of the titanium element is 47.88 g/mol. *

This means, in 47.88 grams of titanium, there is one mole or 6.022 x 10^{23} titanium atoms.

In other words, the mass of one mole or 6.022 x 10^{23} titanium atoms is 47.88 grams.

### how to calculate the molar mass of a compound? | molar mass of NaCl

To calculate the molar mass of a compound with multiple atoms, the molecular mass of the compound (i.e., the *sum of all the atomic mass of the constituent element atoms*) is to be considered.

*For example, let’s see how to find out the molar mass of NaCl. *

The atomic mass of sodium(Na) is 22.99 u and that of chlorine(Cl) is 35.45 u. The sum of these two atomic masses is 58.44 u.

In other words, the molecular mass of NaCl is 58.44 u. *Hence, the molar mass of NaCl is 58.44 g/mol.*

**Formula of Molar mass of a gaseous substance** in terms of its density

Let’s see how to express the *Formula of Molar mass of a gaseous substance in terms of its density*.

The molar mass of an ideal gas can be calculated from the ideal gas equation as :

*p*V = *n*RT …………….. (1)

Now, number of moles (n) = Mass of substances (m ) / Molar mass (M)

n = m/M ………………….(2)

Now, from equations (1) and (2) we get:

*p*V = *n*RT

or *p**V*=* (m/M) *RT

or pV = (mRT)/M

or M = (mRT) / (pV) = dRT/p,

**M = molar mass = dRT/p**

[ where, m/V = mass/volume = density = d ]