### Avogadro’s law definition and explanation

Avogadro’s law definition and explanation is listed below :

Avogadro’s law states that equal volumes of different gases, under the same conditions of temperature and pressure, contain the same number of molecules.

Avogadro’s law is included in a more general law: the law of “ideal gases” which reads as follows:

The amount of gas matter (or “number of moles”) is

-proportional to the volume of gas.

-proportional to the gas pressure.

– inversely proportional to the temperature.

But it is independent of the nature of the gas.

We thus obtain:

n = PV / RT

SI units: n (mol), P (Pa), V (m3), T (K)

R is the constant of ideal gases independent of the nature of the gas

R = 8.31J.K ^{-1} · mol ^{-1}

A gas is considered “perfect” if it strictly follows the previous law. A gas is never “perfect” but it is all the closer to this model the further it is from the liquefaction conditions.

One mole occupies approximately a volume of 22.4 liters at normal temperature and pressure conditions (CNTP), which corresponds to a pressure of 1 atmosphere or 1013 h Pa (hectopascal) and a temperature of 0 ° C.

Under the usual conditions of temperature and pressure (in the laboratory for example)), one mole of gas occupies approximately 24.0 liters, the pressure is at 1 bar and the temperature at approximately 20 ° C.

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