Nitrogen - a chemical element in the periodic system, designated by the letters N and having a sequence number 7. There is a molecule N2, consisting of two atoms.This chemical is a colorless, odorless and tasteless gas, it is inert under standard conditions.The density of nitrogen under normal conditions (0 ° C and a pressure of 101.3 kPa) is equal to 1,251 g / dm3.Element is a part of the earth's atmosphere in an amount of 78.09% of its volume.It was first discovered as a component of air Scottish physician Daniel Rutherford in 1772.
Liquid nitrogen is a cryogenic liquid.At atmospheric pressure it boils at - 195.8 ° C.Therefore, it can be stored only in isolated vessels, which are steel cylinders for liquefied gases or Dewar vessels.Only in this case it can be stored or transported without any loss due to evaporation.As dry ice (liquefied carbon dioxide, also known as carbon dioxide), liquid nitrogen is used as refrigerant.In addition, it is used for cryopreservation of blood, reproductive cells (sperm and oocytes), and other biological samples and materials.He is in demand and in clinical practice, for example, in the cryotherapy in removing cysts and warts on the skin.The density of the liquid nitrogen is equal to 0.808 g / cm3.
Many industrially important compounds such as nitric acid, ammonia, organic nitrates (explosives, fuels) and cyanides comprise N2.Extremely strong ties elemental nitrogen in the molecule cause difficulties for its participation in chemical reactions, it is due to its inertia under standard conditions (temperature and pressure).Especially for these reasons, and N2 is of great importance in many industrial and scientific fields.For example, it is necessary to maintain in situ pressure for oil or gas.Any its practical or scientific applications, demands to know what is the density of nitrogen at a particular pressure and temperature.From the laws of physics and thermodynamics it is known that at constant volume with increasing temperature and will increase the pressure of the gas density, and vice versa.
When and why you need to know the density of the nitrogen?The calculation of this indicator is used in the design of processes that occur with the use of N2, in the laboratory and production.Using the known value of the density of the gas, it is possible to calculate the mass of a certain volume.For example, it is known that the gas occupies under normal conditions, the volume of 20 dm3.In this case, it is possible to calculate the weight: m = 20 • 1,251 = 25,02 g If the conditions differ from standard and known volume of N2 under these conditions, it must first find (for directories), the density of nitrogen at a given pressure and temperature, andthis value is then multiplied by the volume occupied by the gas.
Similar calculations carried out on the production in compiling material balances of process units.They are necessary for the conduct of technological processes, the choice of instrumentation, the calculation of technical and economic parameters, and more.For example, after stopping all chemical production units and pipelines must before their opening and the terminal repair purged with an inert gas - nitrogen (it is the cheapest and most affordable in comparison, for example, helium or argon).As a rule, they are blown so many N2, which is several times greater than the volume of devices or pipes, the only way to uninstall the combustible gases and vapors and to avoid an explosion or fire.When planning the operation stops before the repair, technology, knowing the volume of the system is emptied and density of nitrogen, expects a lot N2, which is required for purging.
To simplify the calculations that do not require precision, real gases equate to an ideal gas and apply the law of Avogadro.Since the mass of 1 mole of N2 is numerically equal to 28 grams, and 1 mole of any ideal gas occupies a volume of 22.4 liters, the density of nitrogen would be equal to 28 / 22.4 = 1.25 g / l = 1.25 g / dm3.This method is applicable to quickly find the density for each gas, not only N2.It is often used in analytical laboratories.