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Phosphorus pentoxide crystallizes in at least four forms or polymorphs.The most familiar one, a metastable form [1] (shown in the figure), comprises molecules of P 4 O 10.Weak van der Waals forces hold these molecules together in a hexagonal lattice (However, in spite of the high symmetry of the molecules, the crystal packing is not a close packing [2]).
Tetrapolyphosphoric acid H 6 P 4 O 13 yields at least six anions, including tetrapolyphosphate [P 4 O 13] 6−, and so on. Note that each extra phosphoric unit adds one extra P atom, three extra O atoms, and either one extra hydrogen atom or an extra negative charge. Branched polyphosphoric acids give similarly branched polyphosphate anions.
At pH 1 or lower, the phosphoric acid is practically undissociated. Around pH 4.7 (mid-way between the first two pK a values) the dihydrogen phosphate ion, [H 2 PO 4] −, is practically the only species present. Around pH 9.8 (mid-way between the second and third pK a values) the monohydrogen phosphate ion, [HPO 4] 2−, is the only species ...
Conversion and its related terms yield and selectivity are important terms in chemical reaction engineering.They are described as ratios of how much of a reactant has reacted (X — conversion, normally between zero and one), how much of a desired product was formed (Y — yield, normally also between zero and one) and how much desired product was formed in ratio to the undesired product(s) (S ...
It is incompatible with alkaline chemicals because its ammonium ion is more likely to convert to ammonia in a high-pH environment. The average pH in solution is 7.5–8. [5] The typical formulation is 18-46-0 (18% N, 46% P 2 O 5, 0% K 2 O). [5] DAP can be used as a fire retardant.
In both cases the phosphoric acid solution usually contains 23–33% P 2 O 5 (32–46% H 3 PO 4). It may be concentrated to produce commercial-or merchant-grade phosphoric acid, which contains about 54–62% P 2 O 5 (75–85% H 3 PO 4). Further removal of water yields superphosphoric acid with a P 2 O 5 concentration above 70% (corresponding to ...
The second number ("P value") is the percentage by weight of phosphorus pentoxide P 2 O 5. The third number ("K value") is the equivalent content of potassium oxide K 2 O. [3] For example, a 15-13-20 fertilizer would contain 15% by weight of nitrogen, 13% by weight of P 2 O 5, 20% by weight of K 2 O, and 52% of some inert ingredient.
2 h(po 4) 2− ⇌ (p 2 o 7) 4− + h 2 o The condensation is shown as an equilibrium because the reverse reaction, hydrolysis , is also possible. The process may continue in steps; at each step another (PO 3 ) − unit is added to the chain, as indicated by the part in brackets in the illustration of polyphosphoric acid.