Stoichiometry: 3.13 - Avogadro's constant (L)

Due to the incredibly small size of the basic particles of matter there are fantastic numbers of them in the masses used in everyday life. Amedeo Avogadro is the scientist most credited with work done in this domain.

Syllabus reference

Structure 1.4.1 - The mole (mol) is the SI unit of amount of substance. One mole contains exactly the number of elementary entities given by the Avogadro constant.

Convert the amount of substance, n, to the number of specified elementary entities.

Guidance

An elementary entity may be an atom, a molecule, an ion, an electron, any other particle or a specified group of particles.
The Avogadro constant NA is given in the data booklet. It has the units mol^–1.

Tools and links

Avogadro's number

Avogadro's number

Avogadro defined the number of particles of a substance that have a mass equivalent to the relative mass of that substance. He found that the number of atoms in 12 g of carbon was equal to approximately 6.02 x 10²³

This number was given his name - the Avogadro constant.

Avogadro's number = 6.02 x 10²³

An Avogadro number of particles = 6.02 x 10²³ particles

The Avogadro number or constant may be represented by the letter 'L' and when dealing with this number of particles we say that there is an 'amount' of 1 mole.

1 mole of any substance contains an Avogadro number of particles of that substance = 6.02 x 10²³ particles

Examples:

1 mole of iron contains 6.02 x 10²³ iron atoms

1 mole of chlorine gas contains 6.02 x 10²³ chlorine molecules

1 mole of electrons contains 6.02 x 10²³ electrons (also called a Faraday of charge)

Note that the Avogadro constant simply describes a specific number of any particle, be they atoms, molecules, electrons or even armchairs!

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