Ca 3 (PO 4) 2 + 3SiO 2 + 5C = 3CaSiO 3 + 5CO + P 2
Phosphorus vapor at this temperature consists almost entirely of P2 molecules, which upon cooling condense into P4 molecules.
When vapor condenses, it forms white (yellow) phosphorus, which consists of P 4 molecules having the shape of a tetrahedron. It is a highly reactive, soft, waxy, pale yellow substance, soluble in carbon disulfide and benzene. In air, phosphorus ignites at 34 o C. It has the unique ability to glow in the dark due to slow oxidation to lower levels. It was white phosphorus that was once isolated by Brand.
If white phosphorus is heated without access to air, it turns into red (it was first obtained only in 1847). Name red phosphorus refers to several modifications that differ in density and color: it ranges from orange to dark red and even purple. All varieties of red phosphorus are insoluble in organic solvents; compared to white phosphorus, they are less reactive (they ignite in air at t>200 o C) and have a polymer structure: these are P4 tetrahedra linked to each other in endless chains. “Violet phosphorus” is somewhat different from them, which consists of groups P 8 and P 9, arranged in long tubular structures with a pentagonal cross-section.
At elevated pressure, white phosphorus turns into black phosphorus, built from three-dimensional hexagons with phosphorus atoms at the vertices, connected to each other in layers. This transformation was first carried out in 1934 by the American physicist Percy Williams Bridgman. The structure of black phosphorus resembles graphite, with the only difference being that the layers formed by phosphorus atoms are not flat, but “corrugated.” Black phosphorus is the least active modification of phosphorus. When heated without access to air, it, like red, turns into steam, from which white phosphorus condenses.
White phosphorus is very toxic: a lethal dose is about 0.1 g. Due to the danger of spontaneous combustion in air, it is stored under a layer of water. Red and black phosphorus are less toxic because they are non-volatile and practically insoluble in water.
Chemical properties
The most chemically active is white phosphorus (in the equations of reactions involving white phosphorus, for simplicity, it is written as P, not P 4, especially since similar reactions are possible with the participation of red phosphorus, the molecular composition of which is uncertain). Phosphorus combines directly with many simple and complex substances. In chemical reactions, phosphorus, like , can be both an oxidizing agent and a reducing agent.
How oxidizer phosphorus reacts with many to form phosphides, for example:
2P + 3Ca = Ca 3 P 2
P + 3Na = Na 3P
Please note that it practically does not combine directly with phosphorus.
How reducing agent phosphorus interacts with halogens, sulfur (i.e. with more electronegative non-metals). In this case, depending on the reaction conditions, both phosphorus (III) compounds and phosphorus (V) compounds can be formed.
a) with slow oxidation or with a lack of oxygen, phosphorus is oxidized to phosphorus oxide (III), or phosphorous anhydride P 2 O 3:
4P + 3O 2 = 2P 2 O 3
When phosphorus burns in excess (or air), phosphorus oxide (V), or phosphorus anhydride P2O5, is formed:
4P + 5O 2 = 2P 2 O 5
b) depending on the ratio of reagents, when phosphorus interacts with halogens and sulfur, halides and sulfides of tri- and pentavalent phosphorus are formed, respectively; For example:
2P + 5Cl 2(g) = 2PCl 5
2P + 3Cl 2(insufficient) = 2PCl 3
2P + 5S (g) = P 2 S 5
2P + 3S (insufficient) = P 2 S 3
It should be noted that phosphorus forms only the PI3 compound with iodine.
Phosphorus plays the role of a reducing agent in reactions with oxidizing acids:
3P + 5HNO3 + 2H2O = 3H3PO4 + 5NO
— with concentrated nitric acid:
P + 5HNO3 = H3PO4 + 5NO2 + H2O
— with concentrated sulfuric acid:
2P + 5H 2 SO 4 = 2H 3 PO 4 + 5SO 2 + 2H 2 O
Phosphorus does not interact with other acids.
When heated with aqueous solutions, phosphorus undergoes disproportionation, for example:
4P + 3KOH + 3H 2 O = PH 3 + 3KH 2 PO 2
8P + 3Ba(OH) 2 + 6H 2 O = 2PH 3 + 3Ba(H 2 PO 2) 2
In addition to phosphine PH 3, as a result of these reactions, salts of hypophosphorous acid H 3 PO 2 are formed - hypophosphites, in which phosphorus has a characteristic oxidation state of +1.
Application of phosphorus
The bulk of the world's phosphorus production is used to produce phosphoric acid, which is used to make fertilizers and other products. Red phosphorus is used in the manufacture of matches; it is contained in the mass that is applied to the matchbox.
Phosphine
The most famous hydrogen compound of phosphorus is phosphine PH 3. Phosphine is a colorless gas with a garlicky odor and is very poisonous. Highly soluble in organic solvents. Unlike ammonia, it is slightly soluble in water. Phosphine has no practical significance.
Receipt
A method for producing phosphine by reacting phosphorus with aqueous solutions was discussed above. Another method is the action of hydrochloric acid on metal phosphides, for example:
Zn 3 P 2 + 6HCl = 2PH 3 + 3ZnCl 2
Chemical properties
- Acid–basic properties
Being slightly soluble in water, phosphine forms an unstable hydrate with it, which exhibits very weak basic properties:
PH 3 + H 2 O ⇄ PH 3 ∙H 2 O ⇄ PH 4 + + OH —
Phosphonium salts are formed only with:
PH 3 + HCl = PH 4 Cl
PH 3 + HClO 4 = PH 4 ClO 4
- Redox properties
The entire list of abstracts can be viewed
*the recording image shows a photograph of white phosphorus
Phosphine formula………………………………………………………….....PH 3
Molecular weight………………………………………………………34.04
Color and appearance................................................... .......Colorless gas.
Melting point................................... - 133.5 °C.
Boiling temperature................................................ .... -87.7°C.
Evaporation pressure........................40 mm Hg. Art. at - 129.4°C.
Solubility in water........................26% by volume at 17°C.
Density........................1.18 (0°C, 760 mmHg) (Air-1).
Flash point................................................... .....100°C.
Lower explosive limit........... 1.79-1.89% of volume;
Odor appears when................................................... ......1.3 - 2.6 ppm.
At relatively high concentrations, phosphine is explosive.
Lower flammability limit (LCFL) – 1.79-1.89%
by volume or ……………………………..26.15-27.60 g/m 3, or 17000-18900 ml/m 3.
The latent heat of evaporation of phosphine is …………………………………102.6 cal/g.
Solubility in water is 0.52 g/l at a temperature of 20 0 C and a pressure of 34.2 kgf/cm 2.
Phosphine
– a highly toxic, colorless gas that is 1.5 times heavier than air, therefore, when used, it easily penetrates into all cracks and hard-to-reach places in the premises and effectively destroys eggs, larvae, pupae and adult insects.
It dissolves poorly in water and does not react with it. Soluble in benzene, diethyl ether, carbon disulfide. Phosphine is highly toxic, affects the nervous system, and disrupts metabolism. MPC = 0.1 mg/m³. The odor is noticeable at a concentration of 2-4 mg/m³; prolonged inhalation at a concentration of 10 mg/m³ is fatal.
Application of phosphine. When carrying out fumigation with phosphine, inorganic preparations based on aluminum and magnesium phosphides are used. The objects and technology for using preparations based on magnesium phosphide are identical to those based on aluminum phosphide. Admission of people and loading of warehouses is permitted after complete ventilation and if the phosphine content in the air of the working area is not higher than the maximum permissible concentration (0.1 mg/m³). Products are sold with a phosphine residue not higher than the MRL (0.1 mg/kg for grain, 0.01 mg/kg for grain processing products).
Phosphine gas is a strong poison for humans and other warm-blooded animals. Acute phosphine poisoning occurs at a concentration in the air of 568 mg/m3. Phosphine gas is highly toxic to insects that pest grain stocks. When working with it, it is advisable to have an understanding of method and mechanism of action on harmful organisms. The maximum permissible concentration (MPC) of phosphine in the air of the working area is 0.1 mg/m3. However, the smell of gas begins to be felt at lower concentrations (about 0.03 mg/m3). The maximum permissible level (ML) of phosphine in grain is 0.01 mg/kg; phosphine residues are not allowed in grain products. Grain and products of its processing can be used for food purposes only if the residual amounts of phosphine in them do not exceed the MRL.
Phosphine gas It is weakly sorbed by grain and grain products, therefore it is easily degassed. At the consumption rates recommended for disinsection, it does not change the quality of the grain and does not impair its seed properties. It was first used in 1934 for the fumigation of grain products. Currently, due to the ban on the use of methyl bromide for fumigation purposes, phosphine is the main fumigant used to control harmful insects.
Phosphorus(from Greek phosphoros - luminiferous; lat. Phosphorus) P, chemical element of group V of the periodic system; atomic number 15, atomic mass 30.97376. It has one stable nuclide 31 P. The effective cross section for capturing thermal neutrons is 18 10 -30 m 2. External configuration electron shell of atom3 s 2 3p 3 ; oxidation states -3, +3 and +5; energy of sequential ionization during the transition from P 0 to P 5+ (eV): 10.486, 19.76, 30.163, 51.36, 65.02; electron affinity 0.6 eV; Pauling electronegativity 2.10; atomic radius 0.134 nm, ionic radii (coordination numbers are indicated in parentheses) 0.186 nm for P 3-, 0.044 nm (6) for P 3+, 0.017 nm (4 ), 0.029 nm (5), 0.038 nm (6) for P 5+ .
The average phosphorus content in the earth's crust is 0.105% by mass, in waters and oceans 0.07 mg/l. About 200 phosphorus minerals are known. they are all phosphates. Of these, the most important is apatite, which is the basis phosphorites. Also of practical importance are monazite CePO 4 , xenotime YPO 4 , amblygonite LiAlPO 4 (F, OH), triphylline Li(Fe, Mn)PO 4 , torbernite Cu(UO 2) 2 (PO 4) 2 12H 2 O, utunite Ca( UO 2) 2 (PO 4) 2 x x 10H 2 O, vivianite Fe 3 (PO 4) 2 8H 2 O, pyromorphite Pb 5 (PO 4) 3 C1, turquoise CuA1 6 (PO 4) 4 (OH) 8 5H 2 ABOUT.
Properties. It is known that St. 10 modifications of phosphorus, the most important of which are white, red and black phosphorus (technical white phosphorus is called yellow phosphorus). There is no uniform designation system for phosphorus modifications. Some properties of the most important modifications are compared in Table. Crystalline black phosphorus (PI) is thermodynamically stable under normal conditions. White and red phosphorus are metastable, but due to the low rate of transformation they can be preserved for an almost unlimited time under normal conditions.
Phosphorus compounds with nonmetals
Phosphorus and hydrogen in the form of simple substances practically do not interact. Hydrogen derivatives of phosphorus are obtained indirectly, for example:
Ca 3 P 2 + 6HCl = 3CaCl 2 + 2PH 3
Phosphine PH 3 is a colorless, highly toxic gas with the smell of rotten fish. A phosphine molecule can be thought of as an ammonia molecule. However, the angle between the H-P-H bonds is much smaller than that of ammonia. This means a decrease in the share of participation of s-clouds in the formation of hybrid bonds in the case of phosphine. Phosphorus-hydrogen bonds are less strong than nitrogen-hydrogen bonds. The donor properties of phosphine are less pronounced than those of ammonia. The low polarity of the phosphine molecule and weak proton-accepting activity lead to the absence of hydrogen bonds not only in liquid and solid states, but also with water molecules in solutions, as well as to the low stability of the phosphonium ion PH 4 +. The most stable phosphonium salt in the solid state is its iodide PH 4 I. Phosphonium salts vigorously decompose with water and especially alkaline solutions:
PH 4 I + KOH = PH 3 + KI + H 2 O
Phosphine and phosphonium salts are strong reducing agents. In air, phosphine burns to phosphoric acid:
PH 3 + 2O 2 = H 3 PO 4
When phosphides of active metals are decomposed by acids, diphosphine P 2 H 4 is formed simultaneously with phosphine as an impurity. Diphosphine is a colorless volatile liquid, similar in molecular structure to hydrazine, but phosphine does not exhibit basic properties. It ignites spontaneously in air and decomposes when stored in light or when heated. Its breakdown products contain phosphorus, phosphine and a yellow amorphous substance. This product is called solid hydrogen phosphide, and the formula P 12 H 6 is assigned to it.
With halogens, phosphorus forms tri- and pentahalides. These phosphorus derivatives are known for all analogues, but chlorine compounds are practically important. RG 3 and RG 5 are toxic and are obtained directly from simple substances.
RG 3 - stable exothermic compounds; PF 3 is a colorless gas, PCl 3 and PBr 3 are colorless liquids, and PI 3 are red crystals. In the solid state, all trihalides form crystals with a molecular structure. RG 3 and RG 5 are acid-forming compounds:
PI 3 + 3H 2 O = 3HI + H 3 PO 3
Both phosphorus nitrides are known, corresponding to the tri- and pentacovalent states: PN and P 2 N 5 . In both compounds, nitrogen is trivalent. Both nitrides are chemically inert and resistant to water, acids and alkalis.
Molten phosphorus dissolves sulfur well, but the chemical reaction occurs at high temperatures. Of the phosphorus sulfides, P 4 S 3 , P 4 S 7 , and P 4 S 10 are the best studied. These sulfides can be recrystallized in a naphthalene melt and isolated in the form of yellow crystals. When heated, sulfides ignite and burn to form P 2 O 5 and SO 2 . With water they all slowly decompose with the release of hydrogen sulfide and the formation of phosphorus oxygen acids.
Phosphorus compounds with metals
With active metals, phosphorus forms salt-like phosphides, which obey the rules of classical valency. p-Metals, as well as metals of the zinc subgroup, give both normal and anion-rich phosphides. Most of these compounds exhibit semiconductor properties, i.e. the dominant bond in them is covalent. The difference between nitrogen and phosphorus, due to size and energy factors, is most characteristically manifested in the interaction of these elements with transition metals. For nitrogen, when interacting with the latter, the main thing is the formation of metal-like nitrides. Phosphorus also forms metal-like phosphides. Many phosphides, especially those with predominantly covalent bonds, are refractory. Thus, AlP melts at 2197 degrees C, and gallium phosphide has a melting point of 1577 degrees C. Phosphides of alkali and alkaline earth metals are easily decomposed by water, releasing phosphine. Many phosphides are not only semiconductors (AlP, GaP, InP), but also ferromagnets, for example CoP and Fe 3 P.
Phosphine(hydrogen phosphide, phosphorus hydride, according to the IUPAC nomenclature - phosphane PH 3) - a colorless, very toxic, rather unstable gas with a specific smell of rotten fish.
Colorless gas. It dissolves poorly in water and does not react with it. At low temperatures it forms a solid clathrate 8РН 3 ·46Н 2 О. Soluble in benzene, diethyl ether, carbon disulfide. At −133.8 °C it forms crystals with a face-centered cubic lattice.
The phosphine molecule has the shape of a trigonal pyramid with molecular symmetry C 3v (d PH = 0.142 nm, HPH = 93.5 o). The dipole moment is 0.58 D, significantly lower than that of ammonia. The hydrogen bond between PH 3 molecules is practically not observed and therefore phosphine has lower melting and boiling points.
Phosphine is very different from its counterpart ammonia. Its chemical activity is higher than that of ammonia; it is poorly soluble in water, as a base is much weaker than ammonia. The latter is explained by the fact that the H-P bonds are weakly polarized and the activity of the lone pair of electrons in phosphorus (3s 2) is lower than that of nitrogen (2s 2) in ammonia.
In the absence of oxygen, when heated, it decomposes into elements:
spontaneously ignites in air (in the presence of diphosphine vapor or at temperatures above 100 °C):
Shows strong restorative properties:
When interacting with strong proton donors, phosphine can produce phosphonium salts containing the PH 4 + ion (similar to ammonium). Phosphonium salts, colorless crystalline substances, are extremely unstable and easily hydrolyze.
Like phosphine itself, its salts are strong reducing agents.
Phosphine is obtained by reacting white phosphorus with hot alkali, for example:
It can also be obtained by treating phosphides with water or acids:
Synthesis directly from elements is possible:
When heated, hydrogen chloride reacts with white phosphorus:
Decomposition of phosphonium iodide:
Decomposition of phosphonic acid:
or its restoration.
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Preparation of phosphine
When white phosphorus is heated with a strong alkali solution, the phosphorus disproportionates, resulting in the formation of phosphate and phosphine PH 3. Simultaneously with phosphine, a small amount of diphosphine P 2 H 4 (a phosphorous analogue of hydrazine) is formed, which easily flares up in air. At the same time, hydrogen is formed. If the gas outlet tube is directed under water, phosphine bubbles flare up to the surface; This produces rings of white smoke.
Here is a description of the experience from the workshop Ripan R. Ceteanu I. Guide to practical work in inorganic chemistry .
Preparation of hydrogen phosphide by heating white phosphorus with a 30-50% solution of potassium hydroxide. Reaction equation:
4P + 3KOH + 3H 2 O = PH 3 + 3KH 2 PO 2
With this method of production, in addition to gaseous hydrogen phosphide, liquid hydrogen phosphide, gaseous hydrogen and acid potassium hypophosphite are also formed according to the equations:
6P + 4KOH + 4H 2 O = P 2 H 4 + 4KH 2 PO 2
2P + 2KOH + 2H 2 O = H 2 + 2KH 2 PO 2
Liquid hydrogen phosphide, interacting with potassium hydroxide in an aqueous environment, forms gaseous hydrogen phosphide, hydrogen and acid potassium hypophosphite according to the equations:
2P 2 H 4 + KOH + H 2 O = 3PH 3 + KH 2 PO 2
P 2 H 4 + 2KOH + 2H 2 O = 3H 2 + 2KH 2 PO 2
Acid potassium hypophosphite in an alkaline environment is converted into potassium orthophosphate with the release of hydrogen:
KH 2 PO 2 + 2KOH = 2H 2 + K 3 PO 4
According to the above reaction equations, when white phosphorus is heated with potassium hydroxide, gaseous hydrogen phosphide, hydrogen and potassium orthophosphate are formed.
The phosphine obtained in this way spontaneously ignites. This is because it contains some vapors of self-igniting liquid hydrogen phosphide (diphosphine) and hydrogen.
Instead of potassium hydroxide, you can use sodium, calcium or barium oxide hydrates. Reactions with them proceed in a similar way.
The device is a round-bottomed flask with a capacity of 100-250 ml, tightly closed with a rubber stopper, through which a tube must be tightly passed, directing gaseous products into a crystallizer with water.
The flask is filled to 3/4 of its volume with a 30-50% solution of caustic potassium, into which 2-3 pieces of white phosphorus, the size of a pea, are thrown. The flask is secured in a tripod clamp and, using a gas outlet tube, is connected to a crystallizer filled with water (see figure).
When the flask is heated, potassium hydroxide reacts with white phosphorus according to the above equations.
Liquid hydrogen phosphorous (diphosphine), upon reaching the surface of the liquid in the flask, immediately ignites and burns in the form of sparks; this occurs until the remaining oxygen in the flask is consumed.
When the flask is heated strongly, liquid hydrogen phosphide is distilled and gaseous hydrogen phosphide and hydrogen are ignited above the water. Phosphorous hydrogen burns with a yellow flame, producing phosphorus anhydride in the form of white smoke rings.
At the end of the experiment, reduce the flame under the flask, remove the plug with the outlet tube, stop heating and leave the device under the draft until it cools completely.
Unused phosphorus is thoroughly washed with water and stored for subsequent experiments.
We decided to get phosphine. Caustic soda was poured into a test tube and half filled with water. Some of the alkali remained in the sediment. The test tube was fixed obliquely in a stand, a pea-sized piece of yellow phosphorus was placed in it and closed with a stopper with a gas outlet tube, the end of which was lowered into a crystallizer with water. Started heating.
Gas bubbles began to bubble in the crystallizer. Over time, yellow flashes began, accompanied by popping sounds: the bubbles burst and caught fire in the air. After the outbreaks, beautiful white smoke rings often formed and rose upward.
According to our observations, the experiment worked best when the liquid in the test tube was actively boiling and some of the liquid was transferred into the water of the crystallizer. In some cases, it turned out that flashes occurred less frequently and weaker if the end of the gas outlet tube was lowered too deep into the water.
In general, the “fireworks with smoke rings” lasted up to several minutes. It's safe to say that this is one of the most beautiful experiences.
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