With the concept of "mole" is faced by every student who begins to study chemistry. With more complex concepts, such as molar mass, molar concentration, solvent molarity, it is difficult to understand without knowing what a mole is. It can be concluded that moth is one of the most important concepts in chemistry. Many tasks cannot be solved without determining the number of moles.
Definition
So what is a mole in chemistry? The explanation is quite simple: it is a unit in which the amount of a substance is expressed, one of the SI units. The definition of what a mole is in chemistry can also be formulated as follows: 1 mole is equivalent to as much substance as there are structural particles in 12 g of carbon-12.
It was found that in 12 g of this isotope contains the number of atoms, numerically equal to the Avogadro constant.
Origin of the concept
Having a little understanding of what a mole in chemistry is with the help of definitions, we turn to the history of this concept. As is commonly believed, the term "moth" was introduced by the German chemist Wilhelm Oswald, who received the Nobel Prize in 1909. The word mole is obviously derived from the word molecule.
An interesting fact is Avogadro’s hypothesis that under the same conditions the same amount of substance contains the same amount of different gases, it was put forward long before Oswald, and the constant itself was calculated by Avogadro at the beginning of the 19th century. That is, even though the concept of “mole” did not exist, the very idea of the amount of substance already existed.
Basic formulas
The amount of substance is different, depending on the data of the task. This form has the most common formula in which this value is expressed by the ratio of mass to molar mass:
n = m / M
It is worth saying that the amount of substance is an additive quantity. That is, in order to calculate the value of this quantity for the mixture, you must first determine the amount of substance for each of its elements and add them.
Another formula is used if the number of particles is known:
n = N / N a
If the task indicates that the process occurs under normal conditions, you can use the following rule: under normal conditions, any gas occupies an invariant volume of 22.4 liters. Then you can use the following expression:
nV / V m
The amount of substance is expressed from the Clapeyron equation:
n = pV / (RT)
Knowing what a mole is in chemistry and the basic formulas for determining the number of moles of a substance makes it possible to solve many problems much faster. If you know the amount of substance, you can find the mass, volume, density and other parameters.