# Mole calculator

## How to use our mole calculator?

The mole calculator allows to get the number of moles of a chemical substance by giving its mass and its molecular weight. With these two information, the calculator will show the number of moles.

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## What is a mole?

The mole is defined by the amount of a chemical substance containing exactly 6.022 140 76 x 10^{23} of elementary entity (atoms, ions, molecules, …). This number is the Avogadro number, with as symbol *N*_{A}.

The definition and the value of the Avogadro number (also called the Avogadro constant) have recently changed. The value indicated in our definition is the last value of this constant.

Until the 20 may of 2019, the Avogadro number (and so the mole) were defined as the number of atoms of carbon in 12 grams of Carbon 12. The measured value was 6.022 140 857 x 10^{23} mol^{-1}.

Since the 20 May 2019, the Avogadro number has become a constant fixed by convention to 6.022 140 76 x 10^{23} mol^{-1}.

By consequence, one mole of carbon has the same amounts of atoms as one mole of lead. One mole of water has also the same amounts of molecules as the amounts of atoms of one mole of Mercury.

The mole is very useful to expressed amounts of reactants and products of chemical reactions. For example:

2H_{2} + O_{2} → 2H_{2}O

Is interpreted as 2 moles of hydrogen (H_{2}) and 1 mole of dioxygen (O_{2}) react to form 2 moles of water (2H_{2}O).

## Mole formula

The amount of substance n in moles (mol) can be calculated with the following formula:

*n = m / M*

where

*n*is the amount of the chemical substance in moles (mol)*m*is the mass of the compound in (g)*M*is the molecular weight (g / mol)

## Mole unit

The mole is the SI base unit of the amount of substance containing exactly 6.022 140 76 x 10^{23} of elementary entities. These entities can be atoms, ions, molecules, …

## Mole symbol

The symbol for the mole is mol.