Question

How many particles are in a mole?

Answer 1

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 `1` `"mol"` of pure `""^12"C"` has a mass of exactly `12` `"g"`. The mass of a substance in one 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"`