Before we talk about what is the pressure of an ideal gas, should specify the actual content of the concept of "ideal gas".A concept is characterized by a mathematical model, a universal formula is assumed that the distribution of the potential and kinetic energy of the interacting molecules such that the magnitude of the potential energy can be ignored.Chemical and physical sense is that it is assumed perfectly elastic walls of blood vessels, which is a gas, but also recognized the value of negligible forces of attraction of the molecules, the pulse of their impact on the vessel wall and to each other.
Such an understanding of the essence of an ideal gas is very widely used in solving problems of thermodynamics of gases.
In the physical sense, different varieties of ideal gas: classic, whose properties are determined by the laws of classical mechanics and quantum, the nature of which is derived from the principles of quantum mechanics.
first brought the general equation of the great French physicist Benoit Clapeyron.He has developed and the basic provisions of the doctrine of the ideal gas, which form the basis of all modern theories of learning a variety of gases.
The starting point of this theory is the finding that the pressure of an ideal gas at a constant value according to the linear nature of the scope of the temperature.It is necessary to take into account some conventional assumptions:
- the diameter of a molecule of an ideal gas to the small size of its permissibility neglect;
- momentum between molecules can be transferred only in collisions, so can be ignored and the force of attraction between them;
- the total amount of energy of the gas molecules recognized as a constant in the absence of heat exchange and the work done on the gas.In this case, the pressure of an ideal gas depends on the amount of pulse which are molecular collisions with the walls of the vessel.
During the existence of the teachings of many scientists engaged in the study of physical and chemical nature of the gas, the approach many of them were not the same.This led to the fact that in considering the classification of the physical theory of an ideal gas in terms of the laws that are put in the basis of his research that a physicist - Fermi gas, Bose gas, and others.For example, according to an equivalent approach, considered the gas at the same time satisfy the law, and Boyle and Gay-Lussac: pV = bT, where p - pressure, T - the absolute temperature.Mendeleev's formula provides more than a lengthy presentation about the properties: pV = m / M x RT, where indicated by: R - the gas constant, M - molar mass, m - mass.
One of the earliest and most developed the doctrine of the properties of gas was a description of the properties of the pressure of an ideal gas.But this concept had some shortcomings related to the one-sided approach to the study.Thus, even by measuring the pressure, we can not find out the mean values of the parameters of the kinetic energy of each of the individual molecules, and also the concentration of these molecules in the vessel.Therefore, a more certain option, by using which you can solve the problem.As such the value of physicists was proposed by the temperature.This scalar value in thermodynamics gives an idea in which the thermal state of the system and how its dynamics.But in the theory of gases the temperature is important and how the molecular-kinetic parameters because it describes the behavior of gas molecules in a container, as well as a reflection of their high kinetic energy.This value is called the Boltzmann constant.
to finding the formula of pressure not to enter the complexity of higher mathematics, it is necessary to artificially introduce some simplification:
- the shape of the molecules present in the form of a ball;
- the distance between the molecules present infinitely large, excluding the forces of gravity;
- set the speed of the molecules to average;
- present the vessel wall completely elastic.
this we can derive a formula in which the pressure of a perfect gas will be the quotient of the magnitude of the force acting perpendicular to the vessel wall surface area on which the force acts: p = F / S.
In those cases when we do not simplify the steps to install, how to change the pressure of an ideal gas, this simple formula will need to enter additional values.
