Phosphorus forms very big number various and . Among them, the most stable are phosphorus (V) oxide and the corresponding orthophosphoric, or phosphoric, acid H 3 PO 4.

Phosphorus (V) oxide, or phosphoric anhydride P 2 O 5- white powder, odorless. It is typical in nature. When dissolved in water, it hydrates to form the following acids:

P 2 O 5 + H 2 O \u003d 2HPO 3

P 2 O 5 + 2H 2 O \u003d H 4 P 2 O 7

P 2 O 5 + 3H 2 O \u003d 2H 3 PO 4

How does the acid oxide P 2 O 5 interact with and basic oxides, for example:

P 2 O 5 + 6NaOH \u003d 2Na 3 PO 4 + 3H 2 O

P 2 O 5 + 3BaO = Ba 3 (PO 4) 2

When P 2 O 5 interacts with alkalis, depending on the ratio of reagents, not only medium, but also acidic ones can be formed:

P 2 O 5 + 4NaOH \u003d 2Na 2 HPO 4 + H 2 O

P 2 O 5 + 2NaOH + H 2 O \u003d 2NaH 2 PO 4

Although in P 2 O 5 phosphorus has the highest degree+5 oxidation, phosphorus (V) oxide does not show any pronounced oxidizing properties, since this oxidation state for phosphorus is very stable.

Phosphorus (V) oxide is an excellent water-absorbing and water-removing agent. This is the basis for its use in desiccators (vessels for drying substances), during dehydration reactions, etc.

Phosphoric (orthophosphoric) acid H 3 RO 4- a colorless crystalline substance, melting at a temperature of 42 ° C, very soluble in water. Phosphoric acid is medium strength.

In the laboratory, it is obtained by the oxidation of dilute phosphorus.

In industry, H 3 RO 4 is obtained by the extraction method by treating natural phosphates with sulfuric acid:

Ca 3 (PO 4) 2 + 3H 2 SO 4 \u003d 2H 3 PO 4 + 3CaSO 4

as well as by the thermal method, restoring natural phosphates to free, which is then burned and the resulting P 2 O 5 is dissolved in water.

Phosphoric acid has all common properties acids, but it is much weaker than such oxygen-containing acids as sulfuric and. Unlike these acids, phosphoric acid does not even have significant oxidizing properties, despite the stability of the +5 oxidation state.

The use of phosphoric acid

In addition to the production of fertilizers, phosphoric acid is used in the manufacture of reagents, many organic substances, for the production of catalysts, for the creation of protective coatings for food, in the pharmaceutical industry, etc.

Salts of phosphoric acid

As a tribasic acid H 3 RO 4 forms three rows: medium (normal) salts - phosphates; acidic salts hydrophosphates and dihydrophosphates.

For example, when neutralizing phosphoric acid, depending on the molar ratio and, the following reactions can occur:

H 3 PO 4 + 3NaOH \u003d Na 3 PO 4 + 3H 2 O

H 3 PO 4 + 2NaOH \u003d Na 2 HPO 4 + 2H 2 O

H 3 PO 4 + NaOH \u003d NaH 2 PO 4 + H 2 O

Most medium salts - phosphates - are insoluble in water. The only exceptions are phosphates and. Many acidic salts of phosphoric acid are highly soluble in water, with dihydrogen phosphates being the most soluble.

Phosphate fertilizers

*on the image of the record is the mineral apatite

Phosphorus oxide is a colorless amorphous or glassy substance that exists in three crystalline, two amorphous, and two liquid forms.

Toxic substance. Causes skin burns and irritation of the mucous membrane.

Phosphorus pentoxide is very hygroscopic. Reacts with alcohols, esters, phenols, acids and other substances. During the reaction with organic matter the bonds of phosphorus with oxygen are broken, and organophosphorus compounds are formed. Enters into chemical reactions with ammonia (NH 3) and hydrogen halides with the formation of ammonium phosphates and phosphorus oxyhalides. Forms phosphates with basic oxides.

3D model of a molecule

The content of phosphorus pentoxide in soil and fertilizers

In fact, only salts of orthophosphoric acid H 3 PO 4 are present in the soil, but salts of meta-, pyro- and polyphosphoric acids can also be found in complex fertilizers.

The basis for the formation of orthophosphoric acid is phosphorus pentoxide. That is why, and also due to the fact that plants do not absorb elemental phosphorus, it is conventional to denote the concentration of phosphorus through the content of phosphorus pentoxide.

P2O 5 + 3H2O→ 2 H3PO 4

All salts of orthophosphoric acid and monovalent cations found in the soil (NH 4 +, Na +, K +) and monosubstituted salts of divalent cations (Ca (H 2 PO 4) 2 and Mg (H 2 PO 4) 2) are soluble in water.

Disubstituted salts of divalent cations are insoluble in water, but readily soluble in weakly acidic acids of root exudates and organic acids of microbial activity. In this regard, they are also a good source of P 2 O 5 for plants.

Absorption of phosphorus pentoxide by plants

As mentioned above, in nature the main source of phosphorus is salts of orthophosphoric acid H 3 PO 4 . However, after hydrolysis, pyro-, poly- and metaphosphates are also used by almost all crops.

Hydrolysis of sodium pyrophosphate:

Na 4 P 2 O 7 + H 2 O + 2H + → 2NaH 2 PO 4 + 2Na +

Hydrolysis of sodium tripolyphosphate:

Na 5 P 3 O 10 + 2H 2 O + 2H + → 3NaH 2 PO 4 + 2Na +

Hydrolysis of the metaphosphate ion (in acidic environment):

(PO 3) 6 6- + 3H 2 O → H 2 P 3 O 10 3- + H 2 P 2 O 7 2- + H 2 PO 4 -

Orthophosphoric acid, being tribasic, dissociates three H 2 PO anions - 4 , HPO 4 2- , PO 4 3- . Under conditions of a slightly acid reaction of the environment, it is in them that plants are cultivated, the first ion is most common and accessible, the second ion is less common and the third is practically inaccessible. However, lupine, buckwheat, mustard, peas, sweet clover, hemp and other plants are able to absorb phosphorus from trisubstituted phosphates.

Some plants have adapted to assimilate the phosphate ion from organophosphorus compounds (phytin, glycephosphates, etc.). The roots of these plants secrete a special enzyme (photophthase), which pinches off the phosphoric acid anion from organic compounds, and then the plants absorb this anion. Such plants include peas, beans, corn. Moreover, phosphatase activity increases under conditions of phosphorus starvation.

Many plants can feed on phosphorus from very dilute solutions, up to 0.01 mg/l P 2 O 5 . Naturally, plants can satisfy the need for phosphorus only if the concentration in it is constantly renewed at least at the same low level.

It has been experimentally established that the phosphorus absorbed by the roots is primarily used for the synthesis of nucleotides, and for further movement to the ground part, phosphates again enter the conductive vessels of the root in the form of mineral compounds.

Recalculation of phosphorus content in fertilizers

y = x,% × 30.974 ( molar mass) × 2 / 30.974 (molar mass) × 2 + 15.999 (molar mass O) × 5

X- content of P 2 O 5 in fertilizer, %;

y- P content in fertilizer, %

y = x, % × 0.43643

For example:

the fertilizer contains 40% phosphorus oxide

for recalculation percentage element phosphorus in the fertilizer, you need to multiply the mass fraction of the oxide in the fertilizer by the mass fraction of the element in the oxide (for P 2 O 5 - 0.43643): 40 * 0.43643 \u003d 17.4572%

2.39 g/cm³ Thermal properties T. melt. 420 about C (H-form), 569 (O-form) T. kip. sublimes at 359 (H-form) °C Enthalpy of formation -3010.1 kJ/mol Chemical properties Solubility in water reacts Classification Reg. CAS number (P2O5)
(P 4 O 10) Data is based on standard conditions (25 °C, 100 kPa) unless otherwise noted.

Phosphorus pentoxide, also phosphorus(V) oxide (phosphoric anhydride, phosphorus pentoxide) is an inorganic chemical compound of the acid oxide class with the formulas P 4 O 10 and P 2 O 5 .

Structure

Pairs of phosphorus(V) oxide have the composition P 4 O 10 . solid oxide prone to polymorphism. Exists in an amorphous glassy state and crystalline. For the crystalline state, two metastable modifications of phosphorus pentoxide are known - the hexagonal H-form (a = 0.744 nm, = 87°, space, gr. R3C) and the orthorhombic O-form (a = 0.923 nm, b = 0.718 nm, c = 0.494 nm , spaces, gr. Ppat), as well as one stable orthorhombic O-form (a \u003d 1.63 nm, b \u003d 0.814 nm, c \u003d 0.526 nm, space group Fdd2). Molecules P 4 O 10 (H-form) are built from 4 groups PO 4 in the form of a tetrahedron, the vertices of which are occupied by phosphorus atoms, 6 oxygen atoms are located along the edges, and 4 - along the threefold axis of the tetrahedron. This modification easily sublimates (360°С) and actively interacts with water. Other modifications have a layered polymer structure of PO 4 tetrahedra combined into 10-membered (O-form) and 6-membered (O "-form) rings. These modifications have a higher sublimation temperature (~ 580 ° C) and are less chemically active The H-form changes to the O-form at 300-360°C.

Properties

P 4 O 10 interacts very actively with water (the H-form absorbs water even with an explosion), forming mixtures of phosphoric acids, the composition of which depends on the amount of water and other conditions:

$\backslash mathsf(P\_4O\_(10)\; +\; 6H\_2O\; \backslash rightarrow\; 4H\_3PO\_4)$

When heated, it breaks down into:

$\backslash mathsf(P\_4O\_(10)\; \backslash rightarrow\; P\_4O\_6\; +\; 2O\_2)$

It is also capable of extracting water from other compounds, making it a powerful dehydrator:

$\backslash mathsf(4HNO\_3\; +\; P\_4O\_(10)\; \backslash rightarrow\; 4HPO\_3\; +\; 2N\_2O\_5)$ $\backslash mathsf(4HClO\_4\; +\; P\_4O\_(10)\; \backslash rightarrow\; (HPO\_3)\_4\; +\; 2Cl\_2O\_7)$

Phosphorus(V) oxide is widely used in organic synthesis. It reacts with amides, converting them to nitriles:

$\backslash mathsf(P\_4O\_(10)\; +\; RCONH\_2\; \backslash rightarrow\; P\_4O\_9(OH)\_2\; +\; RCN)$ $\backslash mathsf(P\_4O\_(10)\; +\; 12RCOOH\; \backslash rightarrow\; 4H\_3PO\_4\; +\; 6(RCO)\_2O)$

Phosphorus(V) oxide also interacts with alcohols, ethers, phenols, and others. organic compounds. In doing so, a break occurs P-O-P connections and organophosphorus compounds are formed. Reacts with NH 3 and with hydrogen halides, forming ammonium phosphates and phosphorus oxyhalides:

$\backslash mathsf(P\_4O\_(10)\; +\; 8PCl\_3\; +\; O\_2\; \backslash rightarrow\; 12POCl\_3)$

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Literature

• Akhmetov N. S. "General and inorganic chemistry» M.: graduate School, 2001
• Remy G. "Course of inorganic chemistry" M .: Foreign Literature, 1963
• F. Cotton, J. Wilkinson "Modern inorganic chemistry" M.: Mir, 1969
• Zefirov N.S. and etc. v.5 Tri-Yatr // Chemical Encyclopedia. - M .: Great Russian Encyclopedia, 1998. - 783 p. - ISBN 5-85270-310-9.

An excerpt characterizing Oxide of phosphorus (V)

“What the hell is he doing, hefty merenina,” they said about him.
Once a Frenchman, whom Tikhon was taking, shot him with a pistol and hit him in the flesh of his back. This wound, from which Tikhon was treated only with vodka, internally and externally, was the subject of the most cheerful jokes in the whole detachment and jokes that Tikhon willingly succumbed to.
"What, brother, won't you?" Ali cringed? the Cossacks laughed at him, and Tikhon, deliberately crouching and making faces, pretending to be angry, scolded the French with the most ridiculous curses. This incident had only the effect on Tikhon that, after his wound, he rarely brought prisoners.
Tikhon was the most helpful and man of courage in the party. No one more than him discovered cases of attacks, no one else took him and beat the French; and as a result, he was the jester of all Cossacks, hussars, and he himself willingly succumbed to this rank. Now Tikhon was sent by Denisov, that night, to Shamshevo in order to take language. But, either because he was not satisfied with one Frenchman, or because he slept through the night, he climbed into the bushes during the day, into the very middle of the Frenchmen and, as he saw from Mount Denisov, was discovered by them.

After talking for some more time with the esaul about tomorrow's attack, which now, looking at the proximity of the French, Denisov seemed to have finally decided, he turned his horse and rode back.
- Well, bg "at, tepeg" let's go and dry ourselves, - he said to Petya.
Approaching the forest guardhouse, Denisov stopped, peering into the forest. A man in a jacket, bast shoes and a Kazan hat, with a gun over his shoulder and an ax in his belt, was walking through the forest, between the trees, with long light steps on long legs, with long dangling arms. Seeing Denisov, this man hurriedly threw something into a bush and, taking off his wet hat with drooping brim, went up to the chief. It was Tikhon. Pitted with smallpox and wrinkles, his face with small narrow eyes shone with self-satisfied amusement. He raised his head high and, as if restraining himself from laughter, stared at Denisov.
“Well, where did pg fall?” Denisov said.
- Where had you been? I followed the French,” Tikhon answered boldly and hastily in a hoarse but melodious bass.
- Why did you climb during the day? Beast! Well, didn't you take it?
“I took it,” said Tikhon.
– Where is he?
“Yes, I took him first of all at dawn,” Tikhon continued, rearranging his flat, turned-out feet in bast shoes wider, “and led him into the forest. I see it's not good. I think, let me go, I’ll take another more carefully one.
“Look, rogue, it’s true,” Denisov said to the esaul. - Why didn’t you pg "ivel"?
“Yes, what’s the point of driving him,” Tikhon interrupted angrily and hastily, “not a busy one. Don't I know what you need?
- What a beast! .. Well? ..
“I went after another,” Tikhon continued, “I crawled into the forest in this manner, and I lay down. - Tikhon unexpectedly and flexibly lay down on his belly, imagining in his faces how he did it. “One and do it,” he continued. - I'll rob him in this manner. - Tikhon quickly, easily jumped up. - Let's go, I say, to the colonel. How to make a noise. And there are four of them. They rushed at me with skewers. I attacked them in such a manner with an ax: why are you, they say, Christ is with you, ”Tikhon cried out, waving his arms and frowning menacingly, exposing his chest.
“That’s what we saw from the mountain, how you asked the arrow through the puddles,” said the esaul, narrowing his shining eyes.
Petya really wanted to laugh, but he saw that everyone was holding back from laughing. He quickly turned his eyes from the face of Tikhon to the face of the esaul and Denisov, not understanding what all this meant.
“You can’t imagine arcs,” Denisov said, coughing angrily. “Why didn’t you bring peg?”
Tikhon began to scratch his back with one hand, his head with the other, and suddenly his whole face stretched into a radiant stupid smile, which revealed the lack of a tooth (for which he was nicknamed Shcherbaty). Denisov smiled, and Petya burst into merry laughter, which was joined by Tikhon himself.
“Yes, quite wrong,” said Tikhon. - The clothes are poor on him, where to take him then. Yes, and rude, your honor. Why, he says, I myself am the son of Anaral, I won’t go, he says.
- What a beast! Denisov said. - I need to ask...
“Yes, I asked him,” said Tikhon. - He says: I don't know you well. There are many of ours, he says, but all are bad; only, says, one name. Ahnete, he says, it’s good, you’ll take everyone, ”Tikhon concluded, looking cheerfully and resolutely into Denisov’s eyes.
“Here I’ll pour in a hundred gog” yachs, and you will be the arc “like a cog” chit, ”Denisov said sternly.

Phosphorus oxides. Phosphorus forms several oxides. The most important of them are P4O6 and P4O10. Often their formulas are written in a simplified form as P2O3 and P2O5 (the indices of the previous ones are divided by 2).

Phosphorus (III) oxide P4O6 is a waxy crystalline mass that melts at 22.5 ° C. It is obtained by burning phosphorus with a lack of oxygen. Strong reducing agent. Very poisonous.

Phosphorus (V) oxide P4O10 is a white hygroscopic powder. It is obtained by burning phosphorus in excess air or oxygen. It combines very vigorously with water and also takes water away from other compounds. Used as a dryer for gases and liquids.

Oxides and all oxygen compounds of phosphorus are much stronger than similar nitrogen compounds, which should be explained by the weakening of the non-metallic properties of phosphorus compared to nitrogen.

Phosphorus (V) oxide. P2O5 interacts vigorously with water, and also takes away water from other compounds. That is why P2O5 is widely used as a desiccant various substances from water vapor.

Phosphoric anhydride, interacting with water, forms primarily metaphosphoric acid HPO3:

when boiling a solution of metaphosphoric acid, orthophosphoric acid H3PO4 is formed:

When H3PO4 is heated, pyrophosphoric acid H4P2O7 can be obtained:

P2O5 is a white snowy substance, greedily absorbing

no water, used for drying gases and liquids, and in some cases

yakh for splitting chemically bound water from substances:

2 HNO3 + P2O5 = N2O5 + 2 HPO3

4HClO4 + P4O10 → (HPO3)4 + 2Cl2O7.

Phosphorus(V) oxide is widely used in organic synthesis. It reacts with amides, converting them to nitriles:

P4O10 + RC(O)NH2 → P4O9(OH)2 + RCN

carboxylic acids converts to the corresponding anhydrides:

P4O10 + 12RCOOH → 4H3P04 + 6(RCO)2O

P2O5 + 6RCOOH → 2H3P04 + 3(RCO)2O

It also interacts with alcohols, ethers, phenols and other organic compounds. In this case, the P-O-P bonds are broken and organophosphorus compounds are formed. Reacts with NH3 and hydrogen halides to form ammonium phosphates and phosphorus oxyhalides:

P4O10 + 8PCl3 + O2 → 12Cl3PO

When P4O10 is fused with basic oxides, it forms various solid phosphates, the nature of which depends on the reaction conditions.

Related information:

1. biological rhythms. In 2 vols. T. 1. Per. from English. - M.: Mir, 1984.- 414 p. heat or after a separate 12-hour exposure to low temperature in the rhythm of chirring, several transient cycles were noted
2. biological rhythms. In 2 vols. T. 1. Per. from English. - M.: Mir, 1984.- 414 p. and that lost rhythms are sometimes restored after several weeks (43]
3. When are invoices issued if services are provided or shipment is carried out several times during one tax period (clause 3, article 168 of the Tax Code of the Russian Federation)?

Phosphorus - vital important element from the fifth group periodic table Mendeleev. The chemical properties of phosphorus depend on its modification. The most active substance is white phosphorus, which oxidizes in air. Phosphorus has two valencies (III and V) and three oxidation states - +5, +3, -3.

Phosphorus and compounds

Phosphorus has three allotropic modifications that differ in chemical and physical properties:

• white;
• red;
• the black.

under the phosphorus chemical reactions the most commonly understood is white phosphorus (P 4). Red phosphorus reacts under certain conditions. For example, it reacts with water when heated and under pressure. Black phosphorus is practically inert.

Rice. 1. Luminous white phosphorus.

Phosphorus reacts with simple and complex substances, forming:

• phosphine;
• phosphoric acid;
• phosphides;
• oxides.

Phosphine (PH 3) is a poisonous gas that is poorly soluble in water, an analogue of ammonia. In the absence of oxygen, when heated, it decomposes into simple substances- phosphorus and hydrogen.

Rice. 2. Phosphine.

Phosphoric or orthophosphoric acid (H 3 PO 4) is formed by the interaction of phosphorus or phosphorus (V) oxide with water.

Phosphides are salts formed by interaction with metals or non-metals. They are unstable and easily decomposed by acids or water.

Phosphorus can form two oxides - P 2 O 3 and P 2 O 5.

H 3 PO 4 - acid of medium strength, showing amphoteric properties when interacting with strong acid. Phosphoric acid forms phosphates.

Chemical properties

Main Chemical properties phosphorus and its compounds are described in the table.

Substance	Reaction	Peculiarities	The equation
		With an excess of O 2 forms phosphorus oxide (V)	4P + 5O 2 → 2P 2 O 5; 4P + 3O 2 → 2P 2 O 3
	with metal	Is an oxidizing agent	3Mg + 2P → Mg 3 P 2
	With halogens and non-metals	Does not react with hydrogen	2P + 3S → P 2 S 3
			8P + 12H 2 O → 5RN 3 + 3H 3 RO 2
	With acids		2P + 5H 2 SO 4 → 2H 3 PO 4 + 5SO 2 + 2H 2 O
	With alkalis		P 4 + 3NaOH + 3H 2 O → PH 3 + 3NaH 2 PO 2
		Ignites in air	PH 3 + 2O 2 → H 3 PO 4
	With halogens and non-metals		РН 3 + 2I 2 + 2H 2 O → H(PH 2 O 2) + 4HI
	With acids	Shows the properties of the reducing agent	РН 3 + 3H 2 SO 4 → H 2 (PHO 2) + 3SO 2 + 3H 2 O
	with metals	with active metals	2H 3 PO 4 + 3Ca → Ca 3 (PO 4) 2 + 3H 2
		undergoing dissociation	H 3 PO 4 + H 2 O ↔ H 3 O + + H2PO 4 -
	With alkalis	Forms acidic or alkaline phosphates	H 3 PO 4 + 3NaOH → Na 3 PO 4 + 3H 2 O
	With oxides		2H 3 PO 4 + 3K 2 O → 2K 3 PO 4 + 3H 2 O
			2H 3 PO 4 + 3CaCO 3 → Ca 3 (PO 4) 2 + 3H 2 O + 3CO 2
	With ammonia		H 3 PO 4 + 3NH 3 → (NH 4) 3 PO 4
	With halogens and non-metals		2P 2 O 3 + 6Cl 2 → 4PCl 3 O + O 2; 2P 2 O 3 + 9S → P 4 S 6 + 3SO 2
		Slow to react with cold water and quickly - with hot	P 2 O 3 + 3H 2 O → 2H 3 PO 3
	With alkalis		P 2 O 3 + 4NaOH → 2Na 2 HPO 3 + H 2 O
		Reacts with an explosion	2P 2 O 5 + 6H 2 O → 4H 3 PO 4
	With acids	substitution reaction	4HNO 3 + 2P 2 O 5 → 4HPO 3 + 2N 2 O 5
		Forms metal hydroxides and phosphine	Ca 3 P 2 + 6H 2 O → 3Ca(OH) 2 + 2PH 3
	With acids	substitution reaction	Ca 3 P 2 + 6HCl → 3CaCl 2 + 2PH 3

When heated, phosphorus oxide decomposes. Moreover, P 2 O 3 forms red phosphorus, and P 2 O 5 - phosphorus (III) oxide and oxygen.

Rice. 3. Red phosphorus.

Usage

Phosphorus compounds are widely used:

• fertilizers and detergents are obtained from phosphates;
• phosphoric acid is used to dye fabric;
• phosphorus (V) oxide dries liquids and gases.

Red phosphorus is used in the manufacture of matches and explosives.

What have we learned?

Phosphorus is an active non-metal that reacts with simple and complex substances. As a result of reactions, it forms oxides (III) and (V), phosphine, phosphoric acid and phosphides. Phosphorus compounds react with metals, non-metals, acids, alkalis, water. Phosphorus and its compounds are used in industry and agriculture.

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