Gas

Substance state

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synonym Gaseous (Substance state) generally refers to gas (substance state)

Gas is a compressible and expandable fluid without shape and volume. A gas is a state of matter. Gas and liquid The same is true fluid : It can flow and deform. Different from liquid, gas molecules are far apart and can be compressed and expanded. If not limit (container or force field), the gas can expand , its volume is unlimited. Gaseous atom or molecule They can move freely with each other. Of atoms or molecules of gaseous matter kinetic energy Quite high. The gas form can be determined by volume 、 temperature And its pressure Impact. These elements constitute a number of gas laws, and the three can affect each other.

Chinese name: Gas

Foreign name: gases \ gaseous state
Pinyin: qì tǐ

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Basic meaning

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Gas

Gas includes actual gas and ideal gas Points. An ideal gas is assumed to be a gas molecule There is no interaction between the molecules, and the gas molecules have no volume. When the actual gas pressure is small, the average distance between the molecules is large, the volume of the gas molecules themselves can be ignored, and the temperature is not low, resulting in the average kinetic energy of the molecules is large, the attraction between the molecules can be ignored, and the behavior of the actual gas is very close to the behavior of the ideal gas, It can be treated as an ideal gas. All discussed in the following contents are ideal gases, but it should not be forgotten that the actual gas is different from it, and the conclusions obtained from the discussion with ideal gas are only applicable to the actual situation where the pressure is not high and the temperature is not low Gas 。

Gas properties

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Density of gas

Density of gas (unit: 10kg/m3)
name	0 ℃, density at standard atmospheric pressure	Density in liquid state		Solid
name	0 ℃, density at standard atmospheric pressure	Temperature ℃	density	Temperature ℃	density
hydrogen	0. 00009	－252. 8	0. 0708	-262	0. 0808
nitrogen	0. 00125	－195. 8	0. 805	－252. 5	1. 026
oxygen	0. 00143	-183	1. 14	－252. 5	1. 426
fluorine	0. 001696	-181	1. 11	-223	1. 3
argon	0. 00178	－185. 7	1. 402	-233	1. 65
ozone （O3）	0. 00214	-183	1. 71	-	-
ammonia	0. 00077	－34. 1	1. 557	-102	About 1.9
name	0 ℃, standard atmospheric pressure, density	name	0 ℃, standard atmospheric pressure, density	name	0 ℃, standard atmospheric pressure, density
coal gas	0. 00060	carbon monoxide	0. 00125	chlorine	0. 00321
bromine	0. 00714	atmosphere	0. 00129	Hydrogen chloride	0. 00164
methane	0. 00078	Nitrogen oxide	0. 00134	hydrogen sulfide	0. 00154
acetylene	0. 00117	ethane	0. 00136	carbon dioxide	0. 00198

Viscosity and density of common gases

The viscosity and density values of common gases are summarized in the following table (normal temperature: 25 ℃, normal pressure)

material	English name	density	Dynamic viscosity	Kinematic viscosity
material	English name	kg/m³	μPa·s	mm/s
atmosphere	air	one point one six nine	eighteen point four four eight	fifteen point seven eight seven
ammonia	ammonia	zero point six nine four	ten point zero nine three	fourteen point five three nine
argon	argon	one point six one three	twenty-two point six two four	fourteen point zero three
butane	butane	two point four one six	seven point four zero six	three point zero six five
Butene	1- butene	two point three two seven	eight point one six three	three point five zero seven
carbon dioxide	carbon dioxide	one point seven eight four	fourteen point nine three two	eight point three six nine
carbon monoxide	carbon monoxide	one point one three	seventeen point six four nine	fifteen point six one four
dimethyl ether	dimethyl ether	one point eight nine five	nine point one	four point eight zero one
ethane	ethane	one point two two two	nine point three five four	seven point six five four
ethylene	ethylene (ethane)	one point one three eight	ten point three one eight	nine point zero six six
hydrogen	hydrogen	zero point zero eight one	eight point nine one five	one hundred and nine point six nine
Hydrosulfide	hydrogen sulfide	one point three eight five	twelve point three eight seven	eight point nine four two
Isobutane	isobutane	two point four zero seven	seven point four nine eight	three point one one five
isobutene	isobutene	two point three two seven	eight point zero eight five	three point four seven four
krypton	krypton	three point three eight seven	twenty-five point one three two	seven point four one nine
methane	methane	zero point six four eight	eleven point zero six seven	seventeen point zero seven one
neon	neon	zero point eight one four	thirty-one point one one three	thirty-eight point two three nine
Neopentane	neopentane	three point zero two one	seven point two five nine	two point four zero three
nitrogen	nitrogen	one point one three	seventeen point eight zero five	fifteen point seven five three
Nitrous oxide	nitrous oxide	one point seven eight five	fourteen point eight four one	eight point three one four
oxygen	oxygen	one point two nine two	twenty point five five	fifteen point nine one
Secondary hydrogen	parahydrogen	zero point zero eight one	eight point nine one five	one hundred and nine point six nine
propane	propane	one point eight zero eight	eight point one four six	four point five zero seven
propylene	propylene	one point seven two two	eight point five six	four point nine seven one
R11	-	five point seven four four	ten point one six two	one point seven six nine
R114		seven point one zero nine	ten point eight zero seven	one point five two
R115		six point three four seven	twelve point five one five	one point nine seven two
R116		five point six two six	fourteen point one four eight	two point five one five
R12		four point nine seven one	eleven point eight zero seven	two point three seven five
R124		five point six five one	eleven point five nine three	two point zero five one
R125		four point nine one five	twelve point nine six two	two point six three seven
R13		four point two five two	fourteen point three six two	three point three seven eight
R134a		four point two zero one	eleven point eight one nine	two point eight one three
R14		three point five six three	seventeen point two four four	four point eight three nine
R142b		four point one six	ten point four two one	two point five zero five
R143a		three point four four eight	eleven point zero eight seven	three point two one five
R152a		two point seven two two	ten point zero eight one	three point seven zero four
R218		seven point seven four eight	twelve point four nine	one point six one two
R22		three point five three nine	twelve point six three one	three point five six nine
R227ea		seven point zero five	eleven point five nine one	one point six four four
R23		two point eight four six	fourteen point nine one three	five point two four
R236ea		six point three five four	ten point eight nine seven	one point seven one five
R236fa		six point three three two	ten point nine six	one point seven three one
R245ca		five point six six one	ten point one one seven	one point seven eight seven
R245fa		five point six three nine	ten point three zero three	one point eight two seven
R32		two point one two five	twelve point six one three	five point nine three seven
R41		one point three eight four	ten point nine five five	seven point nine one three
RC318		eight point three one five	eleven point five zero five	one point three eight four
Fumaric acid	trans-2-butene	two point three three four	eight point zero two eight	three point four four
Dichloroiodomethane	trifluoroiodomethane	eight point zero eight two	fourteen point two seven seven	one point seven six seven
xenon	xenon	five point three two four	twenty-two point nine eight four	four point three one seven

Ideal gas equation

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The ideal gas is an imaginary gas. Its characteristics are:

There is no force between gas molecules; The gas molecule itself does not occupy volume; Occurrence between gas molecule and vessel wall Perfectly elastic collision 。 The lower the pressure and the higher the temperature of a real gas, the closer its properties are to an ideal gas. The gas closest to the ideal gas is helium 。

pV=nRT

follow Ideal gas equation of state Is the basic characteristic of ideal gas. There are four variables in the ideal gas state equation - gas pressure p, gas volume V, gas Amount of substance N, temperature T and a constant (R is the universal gas constant, also called Universal gas constant ）As long as three of the variables are determined, the ideal gas is in one state, so this equation is called the ideal gas state equation. The units of temperature T and material quantity n are fixed, K and mol, respectively, while the units of gas pressure p and volume V can be taken in many ways. At this time, the value (including unit) of constant R in the equation of state will change accordingly. When calculating, pay attention to the correct value of R:

Value of unit R of unit volume (V) of pressure (p) (including unit)

Standard atmospheric pressure (atm) L 0.08206L · atm/mol · K

Standard atmospheric pressure (atm) cubic centimeter (cm three ) 82.06cm three ·atm/mol·K

Pascal (Pa) liter (L) 0.008314L · Pa/mol · K

KPa L 8.314L · kPa/mol · K

Pascal (Pa) cubic meter (m three ) 8.314m three ·Pa/mol·K

1 atm=101.325kN/m two ； 1Pa=1N/ m two ； 1N·m=1J； When various physical quantity R=8.314J/mol · K when SI units are used

Example:

From this, we can calculate the volume of ideal gas under standard conditions

Solution:

From pV=nRT:

V=n·R·t/p

=1mol·8.314L·Pa/mol·K·273.16K/101325Pa

=22.41272L

Partial pressure law

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1810 Dalton It is found that the total pressure of the mixed gas is equal to the sum of the pressures generated by placing the concentration of each component gas in the same container. This rule is called Dalton's law of partial pressure 。 In fact, Dalton's law of partial pressure is only true for ideal gases. For actual gases, due to the existence of intermolecular forces, Dalton's law There will be deviations. Therefore, the gas mixture that can meet Dalton's partial pressure law is called the ideal mixture of ideal gas.

GB102.8-82 issued by the National Bureau of Survey adopts the recommendations and regulations of IUPAC mixed gas Partial pressure p of gas B in B Is defined as

p B =x B p

Where x B For gas B mole fraction , p is the total pressure of mixed gas at the same temperature. Then we can get:

p=p one +p two +p three +p four +……+p j +p B =∑p j =∑x j p

The above formula indicates that, mixed gas The total pressure of is equal to partial pressure This formula can be used for any mixed gas.

For an ideal gas, change p total V=n total RT

Visible partial pressure p B It is the pressure displayed when ideal gas B occupies the volume V of mixed gas alone.

Example:

4.4gCO in mixed gas two ,14gN two , and 12.8gO two , the total pressure is 2.026 × 105Pa, calculate the partial pressure of each component gas.

Solution:

First, calculate the volume fraction (mole fraction) of each component gas, and then substitute it into the above formula to get the partial pressure

n(CO two )=4.4g/44g/mol=0.10mol

n(N two )=14g/28g/mol=0.50mol

n(O two )=12.8g/32g/mol=0.40mol

x(CO two )=n(CO two )/[n(CO two )+ n(N two )+ n(O two )]=0.10

x(N two )=n(N two )/[n(CO two )+ n(N two )+ n(O two )]=0.50

x(O two )=n(O two )/[n(CO two )+ n(N two )+ n(O two )]=0.40

p(CO two )=0.10×2.026×10 five Pa=2.0×10 four Pa

p(N two )=0.50×2.026×10 five Pa=1.0×10 five Pa

p(O two )=0.40×2.026×10 five Pa=8.1×10 four Pa

Bauma's law

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Boyle Mallett's law means that at a certain temperature, the volume of a gas is inversely proportional to its pressure. This can be expressed by the following formula:

Gas

Here V is the volume of gas, P is the pressure, and k is a constant.

Charlie's law

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Charlie's law means that when the pressure remains fixed, the volume of gas is proportional to its temperature. That is, as the temperature of the gas increases, its volume also increases. The mathematical expression is:

Gas

Here V is the volume of gas, T is the temperature, and the unit is Absolute temperature scale Kelvin

Toxic gas

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chlorine

Chlorine (Cl2) ① Color odor state: generally, it is a yellow green gas with irritating odor.

② Density: ratio Air density Large, Standard condition 71/22.4=3.17g/L.

③ Liquefiable. It is easy to liquefy when the melting and boiling point is low, the pressure is 101kPa, and the temperature is - 34.6 ℃. Liquid chlorine is golden yellow. If the temperature continues to cool to - 101 ℃, Liquid chlorine It turns into solid chlorine.

④ Solubility: Soluble to Organic solvent , insoluble in saturated salt water. 1 volume of water normal atmospheric temperature 2 volumes of chlorine can be dissolved below to form Chlorine water , resulting Hypochloric acid It has bleachability, can deteriorate protein, and is easy to decompose into Hydrogen chloride 。

Fluorine gas

Fluorine gas is a kind of corrosive 's pale yellow double Atomic gas 。 Fluorine is Electronegativity The strongest element is also a strong oxidant. At room temperature, it can combine with almost all elements and generate a lot of heat energy. Among all elements, fluorine is the most active.

Fluorocarbon picture

Fluorine gas (F2) is a light yellow gas with a special foul smell and is highly toxic. When the temperature is below - 188 ℃, it will coagulate into yellow liquid. It becomes yellow crystal at - 223 ℃. stay normal atmospheric temperature Fluorine can combine with almost all elements: most metals will be corroded by fluorine, alkali metal It will burn in fluorine, even gold can burn in fluorine after being heated! Many nonmetals, such as silicon, phosphorus and sulfur, will also burn in fluorine. If fluorine is introduced into the water, it will take away the hydrogen in the water and release atomic oxygen (2F2+2H20=4HF+O2 ↑). The exception is only platinum, which will not be corroded by fluorine at room temperature (still corroded at high temperature). Therefore, platinum is used as an electrode when fluorine is produced by electrolysis.

In the atomic energy industry, fluorine has an important use: people use fluorine to extract uranium 235 from uranium ore, because uranium and fluorine compounds are very volatile fractionation It can be separated from other impurities to obtain very pure uranium 235. Uranium-235 is the raw material for making atomic bombs. Of all uranium compounds, only fluoride has good volatility.

The most important compound of fluorine is Hydrogen fluoride 。 Hydrogen fluoride is easily soluble in water, aqueous solution call hydrofluoric acid , just as the aqueous solution of hydrogen chloride is called hydrogen Chlorate (commonly known as hydrochloric acid). Hydrofluoric acid is installed in polyethylene In a plastic bottle. If it is put in a glass bottle, the whole glass bottle will be dissolved after a while because it can strongly corrode the glass (4HF+SiO2=SiF4+2H20). People use this feature to coat the glass first paraffin wax And then cut the wax layer with a knife to carve a pattern, and apply hydrofluoric acid. After a while, wash off the residual hydrofluoric acid, scrape off the wax layer, and beautiful patterns will appear on the glass. The engravings on glasses and the scales on glassware are all made of hydrofluoric acid. As hydrofluoric acid will strongly corrode glass, glass equipment cannot be used in hydrofluoric acid manufacturing, but lead equipment must be used.

In industry, hydrogen fluoride is widely used for manufacturing teflon Plastic. Polytetrafluoroethylene, known as the "king of plastics", has good corrosion resistance, even when immersed in Aqua regia And will not be eroded. It is also resistant to high temperatures above 250 ℃ and low temperatures below - 269.3 ℃. It has important applications in such cutting-edge science and technology as atomic energy industry, semiconductor industry, ultra-low temperature research and space rocket. China has successfully trial produced "polytetrafluoroethylene" in 1965. The surface of PTFE is very smooth and does not drip. People use it to make the tip of a fountain pen. After absorbing the ink, they don't need to wipe the ink with paper, because there is no ink on its surface. Hydrogen fluoride is also used for fluorination Organic compound 。 famous Cryogen “ Freon ”Is a compound of fluorine, carbon and chlorine. In the brewing industry, hydrofluoric acid is used to kill some bacteria harmful to fermentation.

Salts of hydrofluoric acid, such as Strontium fluoride , sodium fluoride Stannous fluoride It has a significant inhibitory effect on lactobacilli and is used to manufacture caries prevention toothpaste. The common "strontium fluoride" toothpaste contains about one thousandth of strontium fluoride.

In nature, fluorine is widely distributed, accounting for about 2/10000 of the total weight of the crust. The most important fluorine ore is fluorite —— Calcium fluoride 。 Fluorite is very beautiful, with glassy luster and square block shape. It has light yellow, light green, light blue, purple, black, red and other colors depending on the impurities contained. China has known about fluorite in ancient times and used it to make decorations. Fluorite is widely used to produce hydrogen fluoride and fluorine. In the aluminum smelting industry, a large amount of fluorite is also consumed, because the addition of cryolite (more pure calcium fluoride crystal) can reduce the alumina Melting point of. crude Cryolite Very few. It is made of fluorite. Except fluorite, apatite It also contains 3% fluorine. The average fluorine content in soil is about 2/10000, and that in seawater is about 1/10 million.

In human body, fluorine is mainly concentrated in bones and teeth. In particular, teeth contain 2/10000 fluoride. The fluorine content of oyster shell is about 20 times higher than that of seawater. Plants also contain fluorine, especially onions and beans.

Bromine vapor

See bromine

Iodine vapor

See Iodine

carbon monoxide

See carbon monoxide

Nitrogen dioxide

See Nitrogen dioxide

sulfur dioxide

See sulfur dioxide

Mercury vapor

See mercury

Cyanide gas (CN) 2

Cyanogen, also called cyanogen gas, chemical formula It is (CN) 2, a compound of carbon and nitrogen (N ∨ C-C ∨ N).

Cyanide in Standard status The following is a colorless gas with a bitter almond smell, which is extremely toxic. It is pink when burning flame , blue on the edge side. Cyanide is soluble in water, ethanol Ether 。

Cyanic chemical property And halogen Similar, yes Pseudo halogen (or pseudohalide ）One of. dicyan Will be reduced to highly toxic cyanide 。 Cyanide reacts with hydrogen at high temperature to form Hydrogen cyanide 。 And Potassium hydroxide Reaction formation Potassium cyanide and Potassium cyanate 。 Cyanide is heated to more than 400 ℃ and polymerized into insoluble white solid (CN) x.

Cyanide can be heated by Mercuric cyanide Or slowly drip potassium cyanide solution copper sulphate Prepared in solution.

Cyanide can be used for organic synthesis, disinfection and insecticidal Fumigant 。

Hydrogen cyanide

Hydrogen cyanide (HCN) is a colorless gas, extremely toxic, with a faint taste of bitter almonds. Interestingly, four adults could not smell it at all because of the lack of corresponding genes. Potassium cyanide and Sodium cyanide They are colorless crystals. In the humid air, hydrolysis produce Hydrocyanic acid It has bitter almond flavor.

Hydrogen fluoride

See hydrofluoric acid

Colored gas

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Chlorine (Cl2)

one
Color odor state: usually strong thrill The yellow green toxic gas with odor.
two
Density: chlorine density is 2.5 times of air density, ρ=3.21kg/m3 under standard condition
three
Liquefiable. The melting and boiling point is low. At normal temperature and pressure, the melting point is - 101.00 ° C, and the boiling point is - 34.05 ° C. Pressurizing chlorine to 600~700kPa at normal temperature or cooling it to - 34 ° C at normal pressure can make it become liquid chlorine, namely Cl2. Liquid chlorine is an oily liquid. It and chlorine physical property Different, but chemical property Basically the same.
four
Solubility: soluble in water and easily soluble in Organic solvent (e.g. carbon tetrachloride), insoluble in saturation Salt water 。 1 volume of water normal atmospheric temperature 2 volumes of chlorine can be dissolved below to form Chlorine water (Normally, the chlorine water is yellow green), the density is 3.170g/L, which is higher than the air density.
five
Relative molecular weight: 70.9 (71) 2 Nitrogen dioxide Nitrogen dioxide is a brownish red, highly active gaseous substance. The chemical formula is NO2, red brown gas. It has a density of 1.491, a melting point of - 9.3 ℃, and is soluble in water. It is a strong oxidant. Below 17 ℃, two molecules are often combined together, so it is also called "nitrogen tetroxide or nitrogen peroxide (N2O4)".

Nitrogen dioxide (NO2)

It is brownish red pungent gas at 21.1 ℃. Toxic gas. The density is greater than that of air, and it is easy to liquefy. Soluble in water; Dark brown liquid below 21.1 ℃. When the temperature is below - 11 ℃, it is a colorless solid, and the pressurized liquid is nitrogen tetroxide. Molecular weight 92, melting point - 11.2 ℃, boiling point 21.2 ℃, vapor pressure 101.31kPa (21 ℃), soluble in alkali, carbon disulfide and chloroform, easily soluble in water. The property is relatively stable. Nitrogen dioxide is not an acid oxide. The density of nitrogen dioxide is higher than that of air

Fluorine gas (F2)

Fluorine, the gas element of element fluorine, chemical formula F2, light yellow, corrosive Very strong, even can react with very inactive gold. Fluorine, chemical element, symbol F, is very active in chemical properties and has strong oxidizability.

Bromine vapor (Br2)

Bromine (Latin: Bromum), derived from Greek: β ρ? μο?， It means "the stench of male goats", which is a chemical element, Element symbol Br， The atomic number 35 is a halogen 。 Bromine molecule Standard temperature It is a volatile reddish brown liquid under pressure, and its activity is between chlorine and iodine. Pure bromine bromine 。 Bromine vapor is corrosive and toxic. The color is brown similar to that of nitrogen dioxide.

Iodine vapor (I)

The elemental iodine is purple black crystal, easy to sublimate, and easy to coagulate after sublimation. Toxicity and corrosiveness. Iodine will turn blue and purple when it meets starch. When heated, iodine rises to purple steam, which has a pungent odor and is toxic. After cooling, it will condense into purple black solid, namely iodine.

Ozone (O3)

Ozone is oxygen Allotrope Under normal temperature, it is a blue gas with special odor.

Nitrogen trioxide (N2O3)

Nitrogen trioxide, an oxide of nitrogen, is an acid oxide, toxic, one of the environmental pollutants, and is the acid anhydride of nitrous acid. Reddish brown gas, dark blue at low temperature volatility Liquid or blue solid. Other gaseous metals are mostly non-ferrous. Note that all rare gases are colorless.

Other related

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1、 The lightest gas in the world<hydrogen>

In 1766, a British millionaire named Henry Gavendish discovered a colorless gas hydrogen. This gas is 14 times lighter than air, that is, one cubic centimeter weighs only 0.00008989 grams

2、 The world's heaviest gas<tungsten hexafluoride>

In fact, contrary to many people's belief, radon is not the heaviest gas in the world. Tungsten hexafluoride is a colorless, odorless gas or transparent liquid at different temperatures. With a boiling point of 17.5 degrees, it is a strong fluoride. The formula quantity is 298, which is greater than radon

3、 Gas with maximum solubility in water<ammonia>

Many gases can be dissolved in water. But the solubility of various gases in water is different. Normally, 1 volume of water

It can dissolve 1 volume of carbon dioxide. One volume of water can only dissolve 1/10 volume of hydrogen. The solubility of hydrogen is visible

Very small. In contrast, some gases are much more soluble than carbon dioxide. In 1 Atmospheric pressure 1 volume at 20 ℃

Water can dissolve 2.4 volume hydrogen sulfide Gas or 2.5 volume chlorine 。 Ammonia is the most soluble gas. It is an irritant

Odorous gas, at 1 atmospheric pressure and 20 ℃, 1 volume of water can dissolve about 700 volumes ammonia 。 The aqueous solution of ammonia is called ammonia 。

Ammonia is an important fertilizer. Ammonia is one of the most important products in modern industry, which can be used to produce nitric acid explosive Etc,

It can also be used to manufacture medicines. Ammonia has other properties: it is easy to gasify, and when the pressure drops, it can evaporate rapidly

Easy liquefaction At - 33 ℃, it will coagulation It becomes a colorless liquid and releases a lot of heat at the same time.

4、 The asteroid "Dragon Palace" brought back gas

In 2022, The Hayabusa 2 probe of Japan Aerospace Exploration Agency brought back gas from the asteroid "Dragon Palace" for the first time^[1] 。

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