Water-soluble fertilizers. Ca3 (PO4) 2 graphical formula
B) yellow.
2. Write the equations of reactions leading to a change in the acidity of the medium (pH) in a solution of sodium orthophosphate.
Solution:Let's write the equations:
From RO 4 + H 2 O:
PO 4 −3 + H 2 O → NRO 4 2− + OH -
NRO 4 2− + Н 2 О → Н 2 РО 4− + ОН -
H 2 PO 4 - + H 2 O → H 3 PO 4 + OH -
Consequently, the medium becomes alkaline.
3T. Calcium phosphide formula A) Ca 3 (PO 4) 2 B) Ca (PO 3) 2 C) Ca 2 P 2 O 7 D) Ca 3 P 2
Answer:D) Ca 3 P 2.
Ca 3 (PO 4) 2 - calcium phosphate;
Ca (PO 3) 2 - calcium phosphite;
Ca 2 P 2 O 7 - calcium pyrophosphate.
4. At what temperature (above or below 100 ° C) does the transformation of orthophosphoric acid into diphosphoric acid take place?
Answer:Conversion of phosphoric acid to diphosphoric acid
occurs at T = 200 ° C.
5. Is the reaction of formation of diphosphoric acid from orthophosphoric acid exo- or endothermic?
Answer:The reaction of formation of diphosphoric acid from orthophos-
fornoy is exothermic.
6. Draw the structural formula of dichromic acid.
Answer:The structural formula of dichromic acid H2Cr2O7 has
). The formed ones are taken off to the refluxed condensers and then collected in the receiver c, under which the molten layer is accumulated.
One of the methods used to obtain PH 3 is heating with strong water. goes, for example, according to the equation:
8Р + ЗВа (ОН) 2 + 6Н 2 О = 2РН 3 + ЗВа (Н 2 РО 2) 3
HgCl 2 + H 3 PO 2 + H 2 O = H 3 PO 3 + Hg + 2HCl
The latter is a white, crystalline-like mass (mp 24 ° C, bp 175 ° C). Its definitions lead to the doubled formula (Р 4 О 6), which corresponds to the shown aa Fig. 125 spatial structure.
Р 2 О 3 + ЗН 2 О = 2Н 3 РО 3
As can be seen from the above comparison, the richest is ortho-acid, which is usually called simply phosphoric. When it is heated, elimination occurs, and pyro- and meta-forms are sequentially formed:
2H 3 PO 4 = H 2 O + H 4 R 2 O 7
H 4 R 2 O 7 = H 2 O + 2HPO 3
ЗР + 5HNO 3 + 2Н 2 О = ЗН 3 РО 4 + 5NO
On an industrial scale, H 3 PO 4 is obtained on the basis of the P 2 O 5 formed during combustion (or it) on, is colorless, spreading to (mp 42 ° C). It is usually sold in the form of 85% water, which has the consistency of a thick syrup. Unlike other derivatives, H 3 PO 4 is not poisonous. Oxidizing properties are not at all typical for it.
NaH 2 PO 4 [primary phosphate]
Na 2 HPO 4 [secondary phosphate]
Na 3 PO 4 [tertiary phosphate]
Ca 3 (PO 4) 2 + 4 3 PO 4 = ZCa (H 2 PO 4) 2
Sometimes, instead of this, NZRO 4 is neutralized, and the so-called. (CaHRO 4 · 2H 2 O), which is also good. On many soils (with an acidic character) it is quite well absorbed by plants directly from finely ground
Simple superphosphate Ca (Н2РО4) 2 · Н2О + 2CaSO4. Powdery (РС) contains 19-20% Р2О5, granular (РСГ) - 19.5-22%. This is the first artificial mineral fertilizer, which began to be produced in 1843 in England, decomposing phosphorites with sulfuric acid.
In Russia, at present, apatite concentrate is obtained by processing with sulfuric acid:
[Ca3 (PO4) 2] 3 · CaF2 + 7H2SO4 + 3H2O → 3Ca (H2PO4) 2 · H2O + 7CaSO4 + 2HF.
Thus, the fertilizer contains about 40% gypsum. Powdered superphosphate is a white or light gray fine powder with a characteristic odor of phosphoric acid. It dissolves poorly in water.
Due to uneven mixing in the reacting mass, other reactions also occur. With a lack of acid, disubstituted calcium phosphate is formed:
[Ca3 (PO4) 2] 3 · CaF2 + 4H2SO4 + 12H2O → 6CaHPO4 · 2H2O + 4CaSO4 + 2HF.
As a result, 10-25% of phosphorus is in a citrate-soluble form.
With an excess of sulfuric acid, phosphoric acid is formed:
[Ca3 (PO4) 2] 3 · CaF2 + 10H2SO4 → 6H3PO4 + 10CaSO4 + 2HF.
Therefore, powdered superphosphate contains 5.0-5.5% free phosphoric acid, which determines the increased acidity and significant hygroscopicity of the fertilizer. Accordingly, it can damp and cake. According to the standard, its moisture content should not exceed 12-15%.
Granular simple superphosphate- these are light gray granules of irregular shape, 1-4 mm in size. During granulation, it is dried to a moisture content of 1-4%, phosphoric acid is neutralized with lime-containing materials (limestone, etc.) or phosphorite, its content is reduced to 1.0-2.5%. Therefore, the physical properties of granular superphosphate are better, it is non-hygroscopic, practically does not cake.
Double (triple) superphosphate Ca (H2PO4) 2 H2O (RSD) contains 43-49% P2O5 (C 76). This is the most concentrated phosphate fertilizer. Available in granular form. The production technology includes two stages: 1) obtaining orthophosphoric acid; 2) treatment with apatite acid (C 80).
Orthophosphoric acid is most often obtained by an extractive method, that is, by decomposition of apatites or phosphorites, including low-percentage ones, with sulfuric acid in accordance with the last reaction (C 79, 81).
A method for obtaining phosphoric acid by means of the following technological processes has also been developed: a) sublimation of phosphorus of low-percentage phosphorites at 1400-1500 ºС, b) combustion of released phosphorus, c) interaction of the formed phosphorus oxide with water (С 81).
The resulting phosphoric acid is used to treat the apatite concentrate:
[Ca3 (PO4) 2] 3 · CaF2 + 14H3PO4 + 10H2O → 10Ca (H2PO4) 2 · H2O + 2HF.
These are light gray or dark gray granules, slightly soluble in water, 1-4 mm in size. The content of free phosphoric acid does not exceed 2.5%, therefore double superphosphate is non-hygroscopic and does not cake.
Enriched superphosphate contains 23.5-24.5% P2O5. Obtained by decomposition of apatite concentrate with a mixture of sulfuric and orthophosphoric acids. Produced in granular form.
Superphos contains 38-40% Р2О5. The production of this fertilizer is based on the interaction of a mixture of sulfuric and phosphoric acids with phosphate rock. Superphos is available in granular form. Water-soluble phosphorus is only half of the total content (19-20%).
When superphosphates are introduced into the soil, chemical, metabolic and biological absorption of phosphorus occurs, therefore it is fixed at the place of application and practically does not move along the soil profile. At the same time, chemisorption greatly reduces the availability of phosphorus to plants.
Superphosphates can be used on all soils for all crops. Simple superphosphate is more expedient to use on soils poorly supplied with sulfur, as well as for legumes and cruciferous plants that are more demanding on sulfur.
As the main fertilizer, superphosphates are best applied in autumn for plowing, but it is also possible in spring for cultivation. To reduce phosphorus retrogradation, local (most often, tape) main application of superphosphates is recommended, which determines their slower interaction with the soil.
One of the recommended methods of using granular forms of superphosphates is pre-sowing application. Sometimes they are also used for feeding. Powdered superphosphate can be used for sowing and feeding only if it has good physical properties, because the damp and caked fertilizer clogs the fertilizer sowing devices of seeders and cultivators-plant feeders.
Semi-soluble fertilizers (soluble in weak acids)
CaHPO4 2H2O precipitate(RP) contains 25-35% P2O5. Obtained by neutralizing solutions of phosphoric acid (waste in the preparation of gelatin from bones) with milk of lime or a suspension of chalk:
H3PO4 + Ca (OH) 2 → CaHPO4 2H2O ↓;
H3PO4 + CaCO3 + H2O → CaHPO4 2H2O ↓ + CO2.
White or light gray finely ground dusty powder, insoluble in water. Accordingly, it is non-hygroscopic and does not cake.
Tomoslak Ca3 (PO4) 2 CaO contains 8-20% P2O5, but the fertilizer used according to the standard must contain at least 14% citrate-soluble phosphorus. The fertilizer contains magnesium, iron and trace elements (manganese, molybdenum, etc.). This is a waste from the metallurgical industry, obtained during the processing of phosphorus-rich cast irons according to the Thomas method. A heavy, finely dispersed powder of dark gray or black color, insoluble in water.
Phosphate slag open-hearth Ca3 (PO4) 2 CaO (RFSh) contains 8-12% P2O5, but the standard provides for the content of citrate-soluble phosphorus in the fertilizer not less than 10% (C 92). Includes iron, magnesium and trace elements. Waste from the processing of phosphorus-rich cast irons by the open-hearth method. Fine dark gray dusty powder. It does not dissolve in water.
Hardly soluble fertilizers. Phosphate flour (phosphate flour)(RF) mainly contains phosphorus in the form of fluorapatite [Ca3 (PO4) 2] 3 · CaF2, in a simplified form its chemical formula looks like Ca3 (PO4) 2. It is obtained by grinding phosphorites to a powdery state so that at least 80% of the product passes through a sieve with a hole diameter of 0.17 mm. This is the cheapest phosphate fertilizer. That is why phosphate rock, with all its shortcomings, is firmly entrenched in the range of phosphorus fertilizers used.
Depending on the phosphorite deposit, the phosphorus content in phosphate rock varies greatly. The highest grade contains at least 30% P2O5, the first - 25, the second - 22, the third - 19% P2O5. This is a finely ground dusty powder of gray, earthy gray, dark gray or brown color, insoluble in water.
The rate of decomposition of phosphate rock depends on the degree of acidity of the soil, the type of phosphorites and the fineness of grinding (C 98).
On soils with a hydrolytic acidity of less than 2.5 meq per 100 g, phosphate is practically insoluble, and phosphorus from it is not assimilated by plants. Therefore, it is recommended to use it on more acidic soils. In this case, it is also necessary to take into account the CEC value, since at the same Hg the effect of phosphate rises with a decrease in the absorption capacity.
It is important that phosphate rock can act on a par with superphosphate if Ng is higher than the calculated value obtained by the formula:
Ng, meq / 100 g of soil = 3 + 0.1 ECO (C 99).
The dependence of the action of phosphate flour on the two considered indicators is clearly shown in the graph of Boris Alexandrovich Golubev (C 100). Thus, a good return on phosphorite flour can be expected when it is used on acidic sod-podzolic, gray forest, peat soils and red soils, as well as on those with high Ng podzolized and leached chernozems. But, using phosphate flour on strongly acidic soils, one should take into account the possibility of retrogradation of water-soluble phosphorus compounds formed during its decomposition.
For the production of phosphate rock, it is more expedient to use nodular phosphorites, younger from a geological point of view, which do not have a well-defined crystalline structure and are easier to decompose. Phosphorites more ancient origin crystalline structure, therefore, their phosphorus is much less available to plants.
The effect of phosphate rock, especially on slightly acidic soils, largely depends on the fineness of grinding. The smaller the particle size, the faster the fertilizer interacts with the soil and the transition of phosphorus to more soluble compounds (C 101, 102).
Phosphoric flour on acidic soils can be applied under all crops, and on neutral soils only under those capable of using phosphorus from trisubstituted phosphates (lupine, buckwheat, mustard, etc.). When applying phosphate flour on neutral soils for other crops, the following methods can be used to decompose phosphate flour (C 103).
1) Composting with peat and manure. Peat in most cases has an acidic reaction that helps to dissolve phosphate rock. In addition, during the decomposition of manure and peat, a significant amount of organic acids is released (C 104).
2) Introduction of phosphate rock on clover. After harvesting clover 2 gp. a lot of stubble-root residues remain. Fosmuk is spread over the surface, disking is carried out, and after a week, plowing. Within a week, the turf decomposes under aerobic conditions with the formation of organic acids.
3) Introduction of phosphate rock into clean steam, in which, as a rule, there is an intensive accumulation of nitrates (nitric acid).
4) Mixing phosphate rock with physiologically acidic fertilizers.
Phosphorite flour is used only for the main application, which, in order to achieve good mixing and long-term interaction with the soil, is best done in the fall under autumn plowing.
Phosphorite flour is also used to improve soil fertility, namely, to increase the content of mobile phosphorus. In this case, high doses of phosphate flour (1-3 t / ha) are used, which are set depending on the acidity of the soil and the initial content of mobile phosphorus. This most important reclamation technique, which provides plants with phosphorus for 6-8 years, is called "phosphorization".
The utilization rates of phosphorus from fertilizer. Phosphorus of water-soluble fertilizers in large quantities is fixed by soils, therefore, in the year of application, plants use only 15-25% of the total amount. Local application of fertilizers increases the phosphorus utilization factor by 1.5-2 times (С 108).
At the same time, phosphorus fertilizers are characterized by a significant aftereffect, that is, they have a positive effect on crop yields for a number of years. For the rotation of a 7-8-field crop rotation, 40-50% of phosphorus of mineral fertilizers is used.
Doses of phosphorus fertilizers.
Phosphate fertilizers are usually applied before sowing and when sowing (planting) crops. In the non-chernozem zone, for the main application for grain crops, an average of 30-90 is used, for row crops and vegetables 60-120 kg / ha P2O5. When sowing, phosphorus is applied in low doses - from 7 to 30 kg / ha P2O5.
Timing and methods of applying phosphorus fertilizers... The main application is best done in autumn under autumn plowing, so that fertilizers get into a deeper soil layer with relatively stable moisture conditions that ensure uninterrupted plant nutrition. It can also be applied in the spring for cultivation, but shallow embedding can lead to the fact that fertilizers end up in the upper, often drying layer of the soil.
Phosphate fertilizers can be stocked for 2-3 years. A single application of 2-3 times increased doses provides plants with phosphorus for 2-3 years, while reducing the cost of using fertilizers.
A universally recommended method of using superphosphates, especially relevant in case of their deficiency, is pre-sowing application, which is desirable to carry out with combined seeders that ensure the placement of fertilizers at a distance of 2.5-3 cm from the seeds in depth or to the side. Granular superphosphate can be applied along with the seeds, but in order to avoid a decrease in their germination when in contact with fertilizer, it is necessary to prepare the mixture immediately before sowing.
For top dressing, as well as for pre-sowing, only water-soluble fertilizers are suitable. One-sided phosphorus fertilization is used very rarely, as a rule, if it was not possible to add a sufficient amount of phosphorus before sowing crops. Therefore, the use of superphosphates for dressing is not widespread. An example of adding superphosphate to top dressing is phosphorus-potassium (mixed with potassium fertilizers) top dressing of perennial legumes. It should be noted that this top dressing is advisable only when low doses of phosphorus are used for cover grasses.
Basically, nitrogen-phosphorus and nitrogen-phosphorus-potassium fertilizing of row crops is carried out, and usually with complex fertilizers.
Example.
Example.
1 mole of Ca 3 (PO 4) 2 weighs as much as its molar mass. M [Ca 3 (PO 4) 2] = 3 · M (Ca) + 2 · M (R) + 8 · M (O) = 3 · 40,078 + 2 · 30,974 + 8 · · 15.999 = 310.174 g / mol.
Mass of 1 mole of Ca 3 (PO 4) 2 or 6.022 · 10 23 Ca 3 (PO 4) 2 molecules is equal to 310.174 g.
Atomic mass unit (amu) (another name is a carbon unit (cu)). It is equal to 1/12 of the mass of an atom of a light isotope of carbon with massive number 12. The atomic mass unit is a constant value equal to 1.6605402 · 10-24 g.
1 amu = m at. (C) = ≈ 0.166 · 10-26 kg.
Units of measurement amu - grams, kilograms, etc.
Mass of atoms and molecules ... m at. , m mol-ly is expressed in very small quantities of the order of 10–26 kg.
m (H) = 0.167 · 10 −26 kg = 1.0079 · a.m.
m (C) = 1.994 · 10 −26 kg = 12.011 · a.m.
m (CO 2) = 7.305 · 10 −26 kg = 12.011 · a.m. + 2 · 15,999 · a.m.
Units of measurement of the masses of atoms and molecules: kg, g, amu. etc.
m at = = A r · a.u .; m mol-ly = = M r · a.m.
m of any number of particles: m (N) = = M · ν.
m at. (C) = 
= 1,992·
10-26 kg;
m at. (C) = 
= 1,994·
10-26 kg.
Relative atomic mass(A r) shows how many times the average mass of an atom of the natural isotopic composition of an element is greater than 1 amu. e.m. Values of А r are given in periodic system elements of DI Mendeleev. And r can be calculated by the formula A r =. And r is a dimensionless quantity. Subscript "r" is the first letter english word relative or Latin relativus - relative, comparative; the mass of the atom is compared to 1 amu.
Superphosphate- this mixture of calcium salts is obtained by treating phosphorites or apatites with a calculated amount of technical sulfuric acid.
Ca 3 (PO 4) 2 + 2H 2 SO 4 = Ca (H 2 PO 4) 2 + 2CaSO 4(Р 2 О 5 »20%)
Useful part superphosphate - water-soluble calcium dihydrogen phosphate, well absorbed by plants. Calcium sulfate is a ballast. Therefore, it is more profitable to obtain double superphosphate.
For this, phosphoric acid is first obtained
Ca 3 (PO 4) 2 + 3H 2 SO 4 = 3CaSO 4 ↓ + 2H 3 PO 4
and then fertilization
Ca 3 (PO 4) 2 + 4H 3 PO 4 = 3Ca (H 2 PO 4) 2- concentrated phosphorus fertilizer.
In addition to superphosphate, a good phosphorus fertilizer for acidic soils is precipitate... It is obtained by neutralizing phosphoric acid with lime.
H 3 PO 4 + Ca (OH) 2 = CaHPO 4 ↓ + 2H 2 O
Calcium hydrogen phosphate is insoluble in water, but soluble in soil acids.
Ammophos - combined fertilizer, includes nitrogen and phosphorus.
NH 3 + H 3 PO 4 = NH 4 H 2 PO 4
2NH 3 + H 3 PO 4 = (NH 4) 2 HPO 4
1) with the P-N connection and 2) without it.
With the P-N bond, they are less stable (energy P-O> energies communication R-N), therefore it is easily oxidized by oxygen.
Phosphate H 3 R +1 O 2 – monobasic, which does not have anhydride (rather strong K = 8.5 * 10 -2).
Salts - hypophosphites - are readily soluble in Н 2 О.
Hypophosphites and H 3 PO 2 are energetic reducing agents (especially in an acidic environment).
Orthophosphorous H 3 +3 PO 3 - H 2 – dibasic, is formed by the interaction of P 4 O 6 with cold H 2 O. This is a crystalline substance, an acid of medium strength K = 8 · 10 -3.
When heated, H 3 PO 3 disproportionates.
4H 3 PO 3 ® 3H 3 PO 4 + PH 3
Pyrophosphorous - Н 4 Р 2 О 5.
Phosphoric acid H 4 R 2 O 6- four basic, medium strength (K = 6.1 · 10 -3), its anhydride is not known.
The compound P 2 O 4 is known, but it, when reacted with H 2 O, gives H 3 PO 3 and H 3 PO 4, i.e. disproportionate like N 2 O 4
Phosphorophosphoric Н 4 Р 2 О 6- tribasic, the same composition as phosphate, but differs in structure.
Biogenic role
Nitrogen in living matter 3 10%, i.e. we live in a nitrogen atmosphere, moderately enriched with oxygen and in very small quantities with other elements.
The term "nitrogen" means lifeless. He received this name for his inertness to reactions with other elements. At the same time, it is known that it is difficult to imagine life on earth without nitrogen, and that nitrogen and life are inseparable concepts.
In the biosphere, nitrogen is formed during bacterial fermentation of protein substances, as well as as a result of the decomposition of nitrogen-containing substances that are part of the mountain population.
It is characteristic that plants and animals consume not free, but bound nitrogen, which is in the soil in the form of nitric acid and ammonium salts.
The functions of transferring free nitrogen into bound nitrogen are performed by nitrogen-fixing bacteria, which, absorbing nitrogen from the air, use it to synthesize proteins and other organic compounds.
Nitrogen compounds, especially nitrates, pollute the biosphere, are harmful to the body and can cause human poisoning. Nitrogen in the soil is in the form inaccessible to plants organic matter, which are decomposed by bacteria into simple compounds NH 3, CO 2, H 2 O, salts. The process of separating ammonia is called ammonization. Ammonia with soil acids form salts that are assimilated by plants.
Atmospheric nitrogen is fixed by nodule bacteria living on the roots of leguminous plants. These bacteria assimilate nitrogen from the air, create nitrogen substances from it, which are used by plants to synthesize proteins.
Phosphorus- belongs to the relatively common elements crust... Clark his 8 · 10 -2%. Fersman called it an element of life and thought. In the body of animals, plants and humans, phosphorus contains from hundredths to tenths to whole percent. Its greatest amount is concentrated in bone tissue (in humans, bones contain 5.05%, in tooth enamel - 17% phosphorus). There is relatively much phosphorus in the brain tissues and muscles. Phosphorus in organisms provides energy processes. With a lack of phosphorus in the body (below 0.1%), bone diseases develop in animals.
Arsenic- v different cases and species acts as a poison and as a healing agent. History gives many cases of the use of arsenic as a poison to poison opponents. Symptoms of arsenic poisoning - metallic taste in the mouth, vomiting, abdominal pain: in case of severe poisoning - convulsions, paralysis, death.
At the same time, arsenic is an essential component of many drugs. In small amounts, salts of arsenic and arsenous acids improve animal nutrition, enhance the processes of assimilation and assimilation of nitrogen and phosphorus.
Arsenic is used by NATO countries to make deadly weapons.
Orthoarsenates are used in agriculture like insecticides.
Na 2 HAsO 4, Na 3 AsO 4
CaHАsO 4, Ca 3 (AsO 4) 2
LECTURE 6
Topic: p - Elements of group VI
