What is molar volume?

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

As can be seen if we analyze the definition that we mentioned in the first paragraph, in order to understand what molar volume is, it is essential to understand what volume is and what is a mole. The notion of molar volume is used in chemistry. Analyzing the concepts of volume and mole The idea of ​​volume can be used in different ways: in this case, we are interested in its meaning as the magnitude that indicates the space occupied by something in height, width and length (that is, in three dimensions ). A mole, in turn, is a unit that allows you to measure the 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, a mole contains an amount of mass that is contained in 6.022 x 10 raised to 23 molecules. This value (6.022 x 10 raised to the power of 23) is called the Avogadro number and is the number of atoms in twelve grams of pure carbon-12. Avogadro’s number allows counting microscopic entities based on microscopic measurements. It is also necessary to know Avogadro’s law, which indicates that when different gases are measured under identical conditions of temperature and pressure, they harbor the same amount of particles. What is molar volume Returning to the idea of ​​molar 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 are maintained. The normal molar volume of gaseous substances is 22.4 liters, estimated at a temperature of 0ºC and a pressure of 1 atmosphere. This occurs in all ideal gas. A mole contains a specific amount of mass. The ideal gas, also known by the name of perfect gases, responds to a law that the particles that form the gas do not attract or repel each other, and when they collide they are perfectly elastic.

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Therefore, the normal molar volume of a gas, whose value is 22.4 liters, only occurs if it is an ideal (or perfect) gas, but not with the so-called common gases; the latter have molecules with volume, although not considerable, which makes their molar volume different from 22.4 liters. In any case, these differences are not very large; for example, while carbon monoxide has this volume, sulfur dioxide and carbon dioxide are 0.5 and 0.1 liters below it, respectively. The notion of partial molar volume Bearing in mind that the volume of a solution is linked to pressure, composition and temperature, and that it is a large quantity, we can define the concept of partial volume as the rate of change of volume as the quantity increases. Of the substance, provided that the values ​​of temperature, pressure and the amount of the other components are kept constant. Partial molar volume is a function of fractional composition, pressure and temperature; in other words, it is an intensive quantity and, according to its definition, we can say that, if pressure and temperature do not vary, it interferes with the differential of the total volume. When we change the composition, for example, we add a certain number of substances, given that the total volume of the mixture increases, the partial molar volumes of its components also change, and it is first done in the surroundings of its molecules. The volume that occupies a number of molecules depends on those that are located nearby.

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