Today, a wide variety of gases are known. A person receives some of them by laboratory methods, from chemicals, some are formed as a result of reactions as by-products. And what gases are born in nature? The main such gases of natural origin are four:
- natural gas whose formula is CH 4 ;
- nitrogen, N 2 ;
- hydrogen, H 2 ;
- carbon dioxide, CO 2 .
Of course, there are some others - oxygen, hydrogen sulfide, ammonia, inert gases, carbon monoxide. However, the above are practically significant for people and are used by them for various purposes, including as fuel.
What is natural gas?
Natural is the gas that nature gives us. That is, one whose content in the bowels of the Earth is much higher and greater than the amount that is obtained in industry as a result of chemical reactions.
Naturally called methane as natural gas, but this is not entirely true. If we consider the composition of such gas by fractions, then we can see its following component composition:
- methane (up to 96%);
- ethane;
- propane;
- butane;
- hydrogen;
- carbon dioxide;
- nitrogen;
- hydrogen sulfide (small, trace amounts).
Thus, it turns out that natural gas is a mixture of several gases of natural origin.
Natural gas: formula
From a chemical point of view, natural gas is a mixture of hydrocarbons of a linear simple structure - methane, ethane, propane and butane. But since methane is still a larger volume, it is customary to express the general formula of natural gas by the formula directly of methane. So, it turns out that the chemical formula of methane natural gas is -CH 4 .
The remaining components have the following empirical formulas in chemistry:
- ethane - C 2 H 6 ;
- propane - C 3 H 8 ;
- butane - C 4 H 10 ;
- carbon dioxide - CO 2 ;
- nitrogen - N 2 ;
- hydrogen is H 2 ;
- hydrogen sulfide - H 2 S.
A mixture of such substances is natural gas. The formula of its main methane compound shows that its carbon content is very small. This affects its physical properties, for example, such as the ability to burn with a colorless, completely non-smoky flame. While other representatives of its homologous series (a number of saturated hydrocarbons or alkanes) during combustion form a black smoking flame.
Being in nature
In nature, this gas is found deep underground, under thick and dense layers of sedimentary rocks. There are two main theories of the origin of natural gas in nature.
- Theory of tectonic rock movements. Proponents of this theory believe that hydrocarbons are always found in the earth's interior and rise as a result of tectonic movements and contractions up. Upstairs, high pressure and changing temperature turn them as a result of chemical reactions into two natural minerals - oil and gas.
- Biogenic theory speaks of another method, as a result of which natural gas was formed. Its formula reflects the qualitative composition - carbon and hydrogen, which suggests that living organic beings took part in its formation, whose bodies were mostly built from these elements, like all living things on our planet that still exist. Over time, the dead remains of animals and plants sank lower and lower to the bottom of the ocean, where there was neither oxygen nor bacteria capable of decomposing and processing this organic mass. As a result of anaerobic oxidation, biomass decayed, and over millions of years two sources of minerals have been formed - oil and gas. In this case, the basis of both is the same - these are hydrocarbons and partially low molecular weight substances. The chemical formula of gas and oil proves this. However, under the influence of different conditions, different products are formed: high pressure and temperature - gas, low indicators - oil.
Today, countries such as Russia, the USA, Canada, Iran, Norway and the Netherlands possess the main gas fields and reserves.
According to its state of aggregation, natural gas cannot always be contained only in the state of gas. There are several options for its condensation:
- Gas is dissolved in oil molecules.
- Gas is dissolved in water molecules.
- Gas forms solid gas hydrates.
- Under normal conditions, a gaseous compound.
Each of these states has its own deposit and is very valuable to humans.
Obtaining in the laboratory and industry
In addition to the natural gas production sites, there are a number of ways to obtain it in the laboratory. However, these methods, of course, are used only for small portions of the product, since it is not profitable to economically synthesize natural gas in the laboratory.
Laboratory methods:
- By hydrolysis of a low molecular weight compound - aluminum carbide: AL 4 C 3 + 12H 2 O = 3CH 4 + 4AL (OH) 3.
- From sodium acetate in the presence of alkali: CH 3 COOH + NaOH = CH 4 + Na 2 CO 3.
- From synthesis gas: CO + 3H 2 = CH 4 + H 2 O.
- Of the simple substances - hydrogen and carbon - at elevated temperature and pressure.
The chemical formula of natural gas is reflected by the formula of methane; therefore, all reactions characteristic of alkanes are also characteristic of this gas.
In industry, methane is obtained by extraction from natural deposits and further processing by fractions. Also, the produced gas needs to be cleaned. After all, the formula of natural gas methane shows only part of those components that it contains. And for domestic use, you need clean gas that does not contain other substances than methane. Separated ethane, propane, butane and other gases are also widely used.
Physical properties
The gas formula gives an idea of what physical properties it should possess. Consider what these characteristics are.
- Colorless, odorless substance.
- The approximate density varies between 0.7-1 kg / m 3.
- Burning temperature 650 0 .
- Almost two times lighter than air.
- The heat generated by the combustion of one cubic meter of gas is 46 million Joules.
- At elevated concentrations (over 15%) in air, gas is very explosive.
- When used as fuel, it displays an octane value of 130.
Pure gas is obtained only after passing it through special treatment plants (plants), which are erected at the place of extraction of the fossil.
Application
There are several main uses for natural gas. Indeed, in addition to its main component, the gas formula of which is CH 4 , all other components of the mixture are used.
1. The household sphere of human life. This includes gas for cooking, heating residential buildings, fuel for boiler rooms and so on. In the gas that is used for cooking, add special substances belonging to the group of mercaptans. This is done so that in the event of a pipe leak or other gas leakage, people can smell it and take measures. A mixture of domestic gas (a mixture of propane and butane) is extremely explosive in high concentrations. Mercaptans also make natural gas specific and odorless. Their formula includes elements such as sulfur and phosphorus, which gives them such specificity.
2. Chemical production. In this area, one of the main initial substances for many reactions to obtain important compounds is natural gas, the formula of which shows which syntheses it can take part in:
- basis for the production of plastics, which are the most common modern material for almost all industries;
- raw materials in the synthesis of ethine, hydrogen cyanide and ammonia. The products themselves are subsequently used in the production of many synthetic fibers and fabrics, fertilizers and insulation in construction;
- rubber, methanol, organic acids - are formed from methane and other substances. Find application in almost all areas of human life;
- polyethylene and many other compounds of a synthetic nature were obtained thanks to methane.
3. Use as fuel. Moreover, for any type of human activity, from refueling the appropriate type of table lamps to the operation of thermal power plants. This type of fuel is considered environmentally correct and appropriate against the backdrop of all alternative methods. However, when burned, methane forms carbon dioxide, like any other organic substance. And he, as you know, the cause of the greenhouse effect of the Earth. Therefore, people are faced with the task of finding an even cleaner and higher quality source of thermal energy.
So far, these are all the main sources that use natural gas. Its formula, if we take all the complex components, shows that it is a practically renewable resource, only this takes a lot of time. Our country with gas reserves is extremely lucky, because such a quantity of natural resources will last for many hundreds of years not only in Russia itself, but also in many countries of the world through export.
Nitrogen
It is an integral part of oil and gas natural deposits. In addition, this gas occupies a large part of the volume in the air (78%), and also occurs as natural nitrate compounds in the lithosphere.
As a simple substance, nitrogen is practically not used by living organisms. Its formula has the form N 2 , or, from the point of view of chemical bonds, N ≡ N. The presence of such a strong bond indicates high stability and chemical inertness of the molecule under ordinary conditions. This explains the possibility of the existence of a large amount of this gas in free form in the atmosphere.
In the form of a simple substance, nitrogen is able to be fixed by special organisms - nodule bacteria. They then process this gas into a more suitable plant form and thus provide mineral nutrition to the root plant systems.
There are several basic compounds in the form of which nitrogen exists in nature. Their formula is as follows:
- oxides - NO 2, N 2 O, N 2 O 5;
- acids - nitrous HNO 2 and nitric HNO 3 (formed during lightning discharges from oxides in the atmosphere);
- saltpeter - KNO 3 , NaNO 3 and so on.
Nitrogen is used by humans not only in the form of gas, but also in a liquid state. It has the ability to go into a liquid state at a temperature below -170 0 C, which allows it to be used to freeze plant and animal tissues, many materials. That is why liquid nitrogen is widely used in medicine.
Nitrogen is also the basis for obtaining one of its main compounds - ammonia. The production of this substance is multi-tonnage, since it is very widely used in everyday life and industry (the production of rubbers, dyes, plastics, synthetic fibers, organic acids, paint and varnish production, explosives, and so on).
Carbon dioxide
What is the formula of the substance? Carbon dioxide is recorded as CO 2 . The bond in the molecule is covalent slightly polar, double strong chemical forces between carbon and oxygen. This indicates the stability and inertness of the molecule under ordinary conditions. This fact is confirmed by the free existence of carbon dioxide in the Earth’s atmosphere.
This substance is an integral part of natural gas and oil, and also accumulates in the upper atmosphere of the planet, causing the so-called greenhouse effect.
A huge amount of carbon dioxide is formed during the combustion of any type of fossil fuel. Whether it is coal, firewood, gas or other fuels, complete combustion leads to the formation of water and this substance.
From this it turns out that its accumulation in the atmosphere is inevitable. Therefore, an important task of modern society is the search for alternative, giving a minimum greenhouse effect of fuel.
Hydrogen
Another associated compound found in natural minerals is hydrogen. A gas whose formula is H 2 . The lightest substance of all known to date.
Due to its special properties, it occupies two positions in the periodic system - among alkali metals and halogens. Having one electron, it is capable of both giving (metallic properties, reducing) and accepting (non-metallic, oxidizing properties).
The main area of use is environmentally friendly fuel, for which scientists see the future. Causes:
- unlimited reserves of this gas;
- the formation of only water as a result of combustion.
However, the full technology for the development of hydrogen as an energy source requires refinement of many more nuances.
Formulas for calculating the mass, density and volume of gases
In physics and chemistry, several basic methods are used for gas calculations. So, for example, if we are talking about one of the most basic parameters, such as the mass of gas, the formula for the calculation will be as follows:
m = V * þ, where þ is the density of the substance, and V is its volume.
For example, if we need to calculate the mass of natural gas with a volume of 1 meter cubic under normal conditions, then we take the standard average value of its density in reference materials. It will be equal to 0.68 kg / m 3 . Now that we know the volume and density of the gas, the calculation formula is quite satisfactory. Then:
m (CH 4 ) = 0.68 kg / m 3 * 1 m 3 = 0.68 kg, as cubic meters are reduced.
The gas volume formula, by contrast, is made up of mass and density indicators. That is, we can express this value from the above configuration:
V = m / þ, then under standard conditions the volume of 2 kg of methane will be equal to: 2 / 0.68 = 2.914 m 3 .
Also in more complex cases (when the conditions are non-standard), the Mendeleev-Clapeyron equation, which has the form:
p * V = m / M * R * T, where p is the gas pressure, V is its volume, m and M are the mass and molar mass, respectively, R is the universal gas constant equal to 8.314, T is the temperature in Kelvin.
Such a formula for gas volume allows one to obtain calculations very close to the value of an ideal gas, which exists purely hypothetically and is used for an abstract concept in solving problems in physics and chemistry. You can also calculate the volume using the Boyle-Marriott equation, which has the form:
V = p n * V n * T / p * T n , where values with index n are values under normal standard conditions.
In order for the calculation to be as accurate as possible and correspond to reality, it is necessary to take into account such a parameter as gas density. The formula for calculating this parameter is still a moot point. It is customary to use the most ordinary simple, which has the form:
þ = m 0 * n, where m 0 is the mass of the molecule (kg), and n is the concentration, the unit of measurement is 1 / m 3 .
However, in some cases it is necessary to use other, more complex and complete calculations with several variables to obtain an accurate and close to ideal result.