Orthophosphoric acid is a type of phosphoric acid, the difference lies in its different structure. Orthophosphoric acid is a phosphoric acid composed of a single phosphorus-oxygen tetrahedron. In the phosphoric acid molecule, the P atom is sp3 hybridized. The three hybrid orbitals form three σ bonds with the oxygen atom. The other P—O bond is composed of a σ bond from phosphorus to oxygen and two σ bonds from oxygen to oxygen. Composed of d-pπ bonds of phosphorus. The σ bond is formed by the coordination of a lone pair of electrons on the phosphorus atom to the empty orbit of the oxygen atom. The d←p bond is formed by the overlap of two lone pairs of electrons in the py and pz orbitals of the oxygen atom and the dxz and dyz empty orbits of the phosphorus atom. Since the 3d energy level of the phosphorus atom is much higher than the 2p energy level of the oxygen atom, the molecular orbital is not very effective, so the P-O bond is a triple bond in terms of number, but intermediate in terms of bond energy and bond length. between single and double bonds. Orthophosphoric acid is obtained by treating apatite with sulfuric acid in industry.
H3PO2, hypophosphorous acid, in which the oxidation number of phosphorus is positive one;
H3PO3, phosphorous acid, in which the oxidation number of phosphorus is positive three;
H3PO4, orthophosphoric acid in which the oxidation number of phosphorus is positive five. In the orthophosphoric acid molecule, there is only one phosphorus-oxygen bond called a triple bond, also called a coordination bond, and there are three phosphorus-oxygen covalent single bonds directly connected to hydrogen, that is, there are three hydroxyl groups;
The phosphorous acid molecule has a hydrogen atom that directly shares an electron pair with the phosphorus atom, a phosphorus-oxygen coordination bond, and a P-O-H bond;
The hypophosphorous acid molecule has two hydrogen atoms that directly share electron pairs with phosphorus atoms, one phosphorus-oxygen coordination bond, and two P-O-H bonds;
According to the delocalization theory, one P-O coordination bond is for one hydroxyl group, one phosphorus-oxygen coordination bond is for two hydroxyl groups, and one phosphorus-oxygen coordination bond is for three hydroxyl groups. Then the acidity is hypophosphorous > hypophosphorous acid Phosphoric acid > Phosphoric acid. That is to say, the degree of ionization of the hydrogen atoms in the hydroxyl group is stronger than that of hypophosphorous acid than that of phosphorous acid than that of phosphoric acid.
Phosphate groups generally appear in organisms. They generally refer to phosphate acyl groups, which are structures in which phosphoric acid removes one hydroxyl group, or it can also be a phosphate group in which two hydroxyl groups are removed. This type of structure is found in many cellular active substances. There are all of them, such as ATP, nucleotides, etc.
Phosphoric acid refers to the inorganic phosphoric acid. In biology, it refers to free phosphate.
Phosphonic acid is a compound in which one or two hydroxyl groups in the phosphoric acid (HO)3PO molecule are replaced by alkyl or aryl groups.
Pure phosphoric acid is a colorless crystal with a melting point of 42.3 degrees Celsius, a high boiling point acid, and is easily soluble in water. Phosphoric acid Commercially available phosphoric acid reagents are viscous, non-volatile concentrated solutions containing 83-98% phosphoric acid.
Phosphoric acid or orthophosphoric acid, chemical formula H3PO4, molecular weight 97.9724, is a common inorganic acid and a medium-strong acid. It can be obtained by dissolving tetraphosphorus decoxide in hot water. Orthophosphoric acid is obtained by treating apatite with sulfuric acid in industry. Phosphoric acid deliquesces easily in the air. Heating will cause water loss to produce pyrophosphoric acid, and further water loss will produce metaphosphoric acid. Phosphoric acid is mainly used in pharmaceutical, food, fertilizer and other industries, and can also be used as a chemical reagent.
Physical properties
Melting point: 42℃
Boiling point: 261°C (decomposed, phosphoric acid gradually dehydrates when heated, so it has no boiling point of its own)
P2O5 and cold water produce metaphosphoric acid, and hot water is phosphoric acid. Phosphoric acid and AgNO3 produce a yellow precipitate, and metaphosphoric acid produces a white precipitate. But only metaphosphoric acid can coagulate the protein aqueous solution to produce a white precipitate.
The most critical point: phosphoric acid is non-toxic but metaphosphoric acid is highly toxic.
Orthophosphoric acid and AgNO3 produce a yellow precipitate, and metaphosphoric acid produces a white precipitate. But only metaphosphoric acid can coagulate the protein aqueous solution to produce a white precipitate.
Phosphoric acid or orthophosphoric acid, chemical formula H3PO4, molecular weight 97.994, is a common inorganic acid and a medium-strong acid. It can be obtained by dissolving phosphorus pentoxide in hot water. Orthophosphoric acid is obtained by treating apatite with sulfuric acid in industry. Phosphoric acid deliquesces easily in the air. Heating will cause water loss to produce pyrophosphoric acid, and further water loss will produce metaphosphoric acid. Phosphoric acid is mainly used in pharmaceutical, food, fertilizer and other industries, including as a rust inhibitor, food additive, dental and orthopedic surgery, EDIC corrosive, electrolyte, flux, dispersant, industrial corrosive, fertilizer raw material and component for household cleaning products. Also used as a chemical reagent, phosphate is a nutrient for all life forms.
After the German businessman Boland discovered phosphorus and the German chemist Konkel prepared phosphorus, the British chemist Boyle also independently prepared phosphorus. He was also the first chemist to study the properties and compounds of phosphorus. He did so in 1682 The paper “A New Experiment on Observed Luminescence” published in 2007 states that “phosphorus generates white smoke after burning, and the solution generated after the white smoke interacts with water is acidic.” The white smoke is phosphoric anhydride (pentaphosphate). Diphosphorus oxide), and the solution generated by the reaction with water is phosphoric acid. However, he did not conduct further research on phosphoric acid.
The earliest chemist to study phosphoric acid was the French chemist Lavoisier. In 1772, he conducted an experiment in which he burned phosphorus in a bell jar sealed with mercury. The experimental results of reverse osmosis bactericide lead to the following conclusion: a certain amount of phosphorus can burn in a certain volume of air; when phosphorus burns, it produces white powder flakes of anhydrous phosphorus, like fine snow; after burning, the air in the bottle is about 80% of the original capacity remains; phosphorus after burning is about 2.5 times heavier than before burning; white powder flakes dissolve in water to form phosphoric acid. Lavoisier also proved that phosphoric acid can be produced by reacting concentrated nitric acid with phosphorus.
About more than a hundred years later, the German chemist Liebig conducted many agricultural chemistry experiments and revealed the value of phosphorus and phosphoric acid to plant life.�In “The Role of Organic Chemistry in Agriculture and Physiology” written by Liebig in 1840, he scientifically demonstrated the problem of soil fertility and pointed out the role of phosphorus on plants. At the same time, he further explored the application of phosphoric acid and phosphates as fertilizers, and from then on the production of phosphoric acid entered the era of large-scale production.
Orthophosphoric acid is a phosphoric acid composed of a single phosphorus-oxygen tetrahedron. In the phosphoric acid molecule, the P atom is sp3 hybridized. The three hybrid orbitals form three σ bonds with the oxygen atom. The other P—O bond is composed of a σ bond from phosphorus to oxygen and two σ bonds from oxygen to oxygen. Composed of d-pπ bonds of phosphorus. The σ bond is formed by the coordination of a lone pair of electrons on the phosphorus atom to the empty orbit of the oxygen atom. The d←p bond is formed by the overlap of two lone pairs of electrons in the py and pz orbitals of the oxygen atom and the dxz and dyz empty orbits of the phosphorus atom. Since the 3d energy level of the phosphorus atom is much higher than the 2p energy level of the oxygen atom, the molecular orbital is not very effective, so the P-O bond is a triple bond in terms of number, but intermediate in terms of bond energy and bond length. between single and double bonds. There are hydrogen bonds in pure H3PO4 and its crystal hydrate, which may be the reason why the concentrated phosphoric acid solution is viscous.
Melting point: 42℃
Boiling point: 261°C (decomposed, phosphoric acid gradually dehydrates when heated, so it has no boiling point of its own)
Commercially available phosphoric acid is a viscous concentrated solution containing 85% H3PO4. Crystallization from concentrated solution forms hemihydrate 2H3PO4·H2O (melting point 302.3K).
Jet (ice) crystal point:
Phosphoric acid is a medium-strong acid with glycerol. Its crystallization point (freezing point) is 21°C. When the temperature is lower than this, semi-hydrated (ice) crystals will precipitate. Of course, usually phosphoric acid does not form (ice) crystals at temperatures above 10°C or even lower. This is due to the supercooling characteristics of phosphoric acid. In fact, commercially available phosphoric acid will deviate from its crystallization (ice) state below 21°C. ) crystal point, the phenomenon of immediate (ice) crystal formation does not exist. However, as long as such a low temperature is maintained for a period of time, phosphoric acid can easily produce ice (ice) crystals in a static state.
Phosphoric acid crystallization, like other liquid crystals, is a physical change rather than a chemical change. Its chemical properties will not change due to crystallization, that is, the quality of phosphoric acid will not be affected by crystallization. As long as it is melted at a certain temperature or diluted and dissolved with heated water, it can still be used normally.
Crystal characteristics: high phosphoric acid concentration, high purity, and high crystallinity. According to experience, when the temperature is around 4 degrees Celsius and the concentration is greater than 85%, its crystallinity increases. If phosphoric acid that has crystallized (ice) crystals is accidentally mixed in, the phosphoric acid that originally did not have crystallized (ice) crystals will immediately become infected and freeze (ice). ) crystals, and phosphoric acid crystallizes (ice) extremely quickly, causing most of the phosphoric acid storage container to freeze (ice) crystals. After phosphoric acid crystallizes (ice), the upper part of the phosphoric acid edge is dilute, and the lower part is deposited with needle-shaped (ice) crystals of pure phosphoric acid. According to experience, 75% phosphoric acid is more difficult to crystallize at lower temperatures (near 4°C). Therefore, under lower temperature conditions, it is recommended to use 75% phosphoric acid.
Phosphoric acid (ice) crystals are like water freezing. They are its own physical properties and inherent attributes and cannot be changed. Only proper storage and handling can prevent (ice) crystals.
