We explain what the mole is and how this magnitude is calculated. In addition, its general characteristics and what is its volume.

To calculate the moles we need to know the atomic or molecular mass.## What is the mole?

The mole is one of the quantities stipulated by theInternational System of Units (YES). Its symbol is "mole".

The mole is defined as the amount of matter containing a certain number of elementary entities (atoms, molecules, etc) equivalent to the number of atoms in 12 grams of the carbon-12 (12C) isotope.

Themass of a mole of substance (called molar mass) is equivalent to the atomic or molecular mass (depending on whether a mole of atoms or molecules has been considered) expressed in grams.

TheAvogadro's number (NA) is the amount of particles (molecules, atoms,electrons) that contains one mole of any substance. It is a constant that corresponds to the value of 6.022 × 10 ^ 23 mol-1. Therefore, 1 mole of any substance contains 6.022 × 10 ^ 23 elemental entities of that substance. On the other hand, Avogadro's number allows us to establish conversions between the gram and the atomic mass unit, where 6.022 × 10 ^ 23 u.m.a (atomic mass unit) is equal to 1 gram. Avogadro's number is the number of atoms contained in 1 mole of atoms whose mass is equal to the atomic mass of the element.

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## How is the mole calculated?

To calculate the moles it is necessary to know the atomic or molecular mass.To calculate the moles it is necessary to know the atomic or molecular mass, depending on whether it is atoms or compounds respectively. So, to calculate the number of moles of molecules or atoms in a substance Either the fraction must be made between the mass of the substance, over its molecular or atomic mass. For example, if we want to calculate the number of moles of X we write:

Where: is the number of moles of X, *m (X)* is the mass of X and *M (X)* is the atomic or molecular mass of X.

## What is the volume of a mole?

When substances are ingaseous state it is possible to calculate the volume that a mole occupies. Volume is a measure of the magnitude of the extension of a body and its unit is the cubic meter (m3) in the SI.

Under normal conditions oftemperature YPressure (T = 25⁰C and P = 1atm), the volume of one mole of gas equals 22.4 liters (L). This value is called *molar volume* (Vm) and corresponds to the so-called ideal gases. Real gases have Vm values slightly different from this value. For example, CO2 has Vm = 22.3L.