Definition of molar volume - What it is, Meaning and Concept

Molar volume is a concept that is used in the field of chemistry .The notion is used to name the volume occupied by one mole of a substance , using as a reference unit the cubic meter per mole .

As can be seen if we analyze the definition mentioned in the first To understand what the molar volume is, it is essential to understand what the volume is and that it is a mol .

The idea of ​​volume can be used in different ways: in this case, we are interested in its meaning as the magnitude indicated by the space occupied by something high, wide and long (that is, in three dimensions).A mole, meanwhile, is a unit that allows the measurement of the existing amount of an element that has a weight equivalent to its molecular weight reflected in grams.

It is important to mention that, in every substance, one mole houses a amount of mass that is contained in 6.022 x 10 raised to 23 molecules .This figure (6.022 x 10 raised to 23) is called Avogadro number and is the amount of atoms in twelve grams of pure carbon-12 . Avogadro number allows you to count microscopic entities based on microscopic measurements.

It is also necessary to know the Avogadro law , which indicates that when different gases are measured in identical conditions of temperature and pressure, they house the same amount of particles.

Taking up the idea of ​​ molecular volume , from what is mentioned by Avogadro's law, it follows that the mole of a gas always occupies the same volume when the conditions of temperature and pressure .The normal molar volume of gaseous substances is 22.4 liters , estimated at a temperature of 0º C and a pressure of 1 atmosphere .This happens in every ideal gas.

The ideal gases , also known as perfect gases , respond to a law according to which the particles that form the gas they do not attract or repel each other, and when they collide they do so perfectly elastic.

Therefore, the normal molar volume of a gas , whose value is 22.4 liters, only occurs if we are faced with an ideal gas (or perfect), but this does not happen with the so-called ordinary gases ; The latter have molecules with volume, although not considerable, and this makes their molar volume different from 22.4 liters.However, it is not very large differences; for example, while carbon monoxide has such volume, sulfur dioxide and carbon dioxide are 0.5 and 0.1 liters below, respectively.

Molar volume partial

Given that the volume of a solution is linked to pressure, composition and temperature, and that it is an extensive magnitude, we can define the concept of partial volume as velocity of volume change as the amount of substance increases, as long as the temperature, pressure and quantity of the rest of the components are kept constant.

Partial molar volume is a function of fractional composition, pressure and temperature; in other words, it is an intensive magnitude and, according to its definition, we can affirm that if the pressure and the temperature do not vary, it intervenes in the differential of the total volume.

When we alter the composition, for example if we add a certain amount of some of the substances, since the total volume of the mixture increases, the partial molar volumes of its components also change, since the environment of its moleculas.The volume that occupies any amount of molecules depends on those around it.