Before looking for the meaning of the phrase "gas law", it is necessary to find out what a gas is. Gases are substances whose particles move randomly in space. These substances are characterized by very weak intermolecular, interatomic and interionic interactions. The gaseous state is also called a gas, that is, one of four, in addition to liquid, solid and plasma, aggregate states of matter. Gases have their own laws. What is the gas law?
Definition
From a physical point of view, gas laws are laws that explain isoprocesses occurring in an ideal gas. An interesting fact is that in chemistry there are also certain patterns for describing such substances that resonate with the laws of physics. However, these laws apply to real gases. Now it’s worth understanding what an ideal gas and an isoprocess are. Let's get started.
Ideal gas
An ideal gas is a mathematical model of a real gas, which assumes that there is no interaction between gas particles. From this assumptionit follows that the particles are in contact only with the vessel in which the substance is located, and also that the mass of the particles of this substance is so small that it can be completely excluded from consideration.
Isoprocesses
To answer the question of what is an isoprocess, you need to turn to thermodynamics (one of the branches of physics). To describe the state of a gas (ideal gas), the main parameters are pressure, temperature and volume.
So, isoprocesses are processes occurring in gases, provided that one of these three parameters remains unchanged over time. In isothermal processes the temperature does not change, in isobaric processes the pressure does not change, and in isochoric processes the volume does not change.
Mendeleev-Clapeyron equation
Before discussing gas laws, it is necessary to know what the Mendeleev-Clapeyron equation is and how this equation relates to gases and their laws. To describe the dependence on each other of all the same indicators - pressure, volume, temperature, the universal gas constant and volume (molar) are also added.
The equation has the following form: pV=RT.
R - universal gas constant, you can calculate it yourself, or you can use the already known value - 8, 3144598(48)J⁄(mol∙K).
Thus, the molar volume is the ratio of volume to the amount of substance (in moles), and the amount of substance, in turn, is the ratio of mass to molar mass.
The equation can be written as followsway: pV=(m / M)RT.
What laws of gases exist in physics
As mentioned earlier, isoprocesses are considered in physics. There are formulas for the dependence of three basic quantities (volume, pressure, temperature) on each other. Gas laws in physics:
- Boyle-Mariotte's law, applied in the case of an isothermal process: the product of pressure and volume of gas remains unchanged over time. Based on the Mendeleev-Clapeyron equation - pV=(m / M)RT=const, this law states that the result of multiplying pressure and volume will be constant, provided that the temperature of the gas and its mass remain unchanged.
- Gay-Lussac's law, which applies to isobaric processes. In this case, the ratio of volume and temperature remains unchanged: V / T=const. Gay-Lussac's law can be formulated as follows: if the pressure and mass of a gas remain unchanged over time, then the quotient of volume divided by temperature is a constant value.
- Charles' law - for isochoric processes. The ratio of pressure and temperature does not change: p / T=const. In this case, the ratio of gas pressure and temperature is constant while pressure and mass remain unchanged.
Gas Laws: Chemistry
Among these laws:
- Avogadro's law. It is formulated as follows: equal volumes of different gases contain the same number of molecules, other things being equal (pressure and temperature). From this law follows -under normal conditions (normal conditions are a pressure of 101.235 kPa and a temperature of 273 K), the volume of absolutely any gas occupied by 1 mole is 22.4 liters.
- D alton's Law: the volumes occupied by gases reacting with each other and products obtained during the reaction, when dividing the first by the second, result in small, but exactly integer numbers, which are called coefficients.
- Law of partial pressures: in order to determine the pressure of a mixture of gases, it is necessary to add the pressures created by the gases of the mixture.
Variety of laws that apply to gases
Perhaps many people think that gases are the simplest of aggregate states: both particles move randomly, and the distance between them is maximum (especially in comparison with solids), and the mass of these same particles is small. However, the laws applied to describe the states of such substances are very diverse. It follows from what has been said above that not only physics deals with the study of the question of gas laws. Moreover, both in physics and in chemistry there are not one or two of them. From this one can come to the conclusion that what seems simple is not always so in reality.
