What is a moth in chemistry? Definition and formulas

With the concept of "moth", every schoolboy comes across who begins to study chemistry. With more complex concepts, such as molar mass, molar concentration, molarity of the solvent, it is difficult to understand without knowing what a mole is. It can be concluded that the mole is one of the most important concepts in chemistry. Many tasks can not be solved without specifying the number of moles.

Definition

So what is a moth in chemistry? The explanation is quite simple: this is the unit in which the amount of substance is expressed, one of the SI units. The definition of what a mole is in chemistry can be formulated in this way: 1 mole is equivalent to the same amount of substance as contains the structural particles in 12 g of carbon-12.

It was found that 12 g of this isotope contains the number of atoms numerically equal to the Avogadro constant.

Origin of the concept

A little understanding of the fact that such a mole in chemistry with the help of definitions, let us turn to the history of this concept. As is commonly believed, the term "mole" was introduced by the German chemist Wilhelm Oswald, who received the Nobel Prize in 1909. The word "mole", obviously, comes from the word "molecule".

An interesting fact - Avogadro's hypothesis that under the same conditions in the same volumes of different gases contains the same amount of matter, was put forward long before Oswald, and the constant itself was calculated by Avogadro at the beginning of the XIX century. That is, although the concept of "mole" did not exist, the very idea of the amount of substance was already there.

Basic Formulas

The amount of substance is different, depending on the task data. This form has the most common formula in which this quantity is expressed by the ratio of mass to molar mass:

N = m / M

It is worth saying that the amount of matter is an additive quantity. That is, to calculate the value of this value for the mixture, you must first determine the amount of matter for each of its elements and add them.

Another formula is applied if the number of particles is known:

N = N / N _a

If the problem states that the process occurs under normal conditions, the following rule can be used: under normal conditions, any gas occupies an invariant volume of 22.4 liters. Then we can use the following expression:

NV / V _m

The amount of matter is expressed by the Clapeyron equation:

N = pV / (RT)

Knowing what a mole is in chemistry and the basic formulas for determining the number of moles of matter makes it possible to solve many problems much faster. If you know the amount of matter, you can find mass, volume, density and other parameters.