How many particles are in a mole?

1 Answer
Nathan L.
Aug 19, 2017

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"#

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