# How many particles are in a mole?

##### 1 Answer

In science, we have a name for this, called **Avogadro's number**, and it describes the number of representative particles in one **mole** of a substance.

Avogadro's number is

#ul(6.022xx10^23 color(white)(l)"mol"^-1#

The inverse mole unit tells us **there are #6.022xx10^23# particles of something *per mole***.

The official definition of the mole is **the quantity that describes the number of elementary entities as there are atoms in #12# #"g"# of isotopically pure carbon-12**.

From this definition, we see that **exactly** **mole** of that substance is called the **molar mass** of that substance.

To find the number of moles of a substance present, we divide the mass of the substance by its molar mass, which we see from the definition of **molar mass**:

#"molar mass" = "mass"/"mol"#

#"mol" = "mass"/"molar mass"#