Monohydrogen phosphate ion

Additional base reacts with the monohydrogen phosphate ion to produce phosphate ion, P043-. When this reaction is complete, the primary species in solution are the phosphate ion and sodium ion, which form a solution of Na3P04(aq). To reach this stoichiometric point, we have to add another mole of base for each mole of acid present (F in the plot). At this point, a total of 3 mol OH has been added for each mole of H3P04. Notice that the third stoichiometric point is not as distinct as the first two, largely because fCa3 is comparable to Kw. 

In the investigation of the cleavage of S-substituted thioureas (24), the increase in the anodic wave of the mercaptans formed can be followed. In this base-catalysed reaction, the reactivities of hydroxyl and carbonate ions are considerably greater than those of the other bases investigated (borate, bicarbonate, ammonia, phosphate and monohydrogen phosphate). There is some analogy with base-catalysed ester hydrolysis. 

Considering the dissociation of phosphate in the pH range investigated (pk - 2.15, pk2 - 7.21, pk3 - 12.67) it becomes clear, that the concentrations of the phosphate, and the monohydrogen phosphate ions are too low to give a substantial contribution to the apparent reaction rate as shown in the formula. The formula may therefore be simplified to ... 

Practice Problem 8.22 What is the charge on the monohydrogen phosphate ion ... 

It is possible to predict the concentrations of the various molecular species in a solution of phosphoric acid, but the calculations involved, which require the simultaneous solution of several equilibrium equations, are rather complicated. In a 1 F solution of phosphoric acid, H3PO4, it is found that the concentration of hydrogen ion and of dihydrogen phosphate ion, H2P04, is 0.083 mole/1, the concentration of monohydrogen phosphate ion, HP04, is 6.2 X 10 moles/1, and the concentration of phosphate ion, P04 -, is 1 X 10 moles/l. 

Dissolved calcium and phosphate ions may remain soluble despite their concentrations exceeding the solubility product in blood plasma and stromal extracellular (interstitial) fluid where the pH is just above 7 (Sect. 3.3.1). In blood plasma, mineralization is prevented by polyanions, especially albumin, citrate, and pyrophosphate (PPi), which chelate calcium ions and prevent their precipitation with monohydrogen phosphate ions (orthophosphate, Pi, or HP042-). Pyrophosphate (PPi) inhibits the premature aggregation of calcium with monohydrogen phosphate ions in mineralizing tissues and interstitial fluid throughout the body (Fig. 9.1b). 

Dihydrogen phosphate and monohydrogen phosphate ions play an important role in maintaining the pH in intracellular fluid. Write equations that show how these... 

Problem A buffered solution maintains acidity as a reaction occurs. In living cells, phosphate ions play a key buffering role, so biochemists often study reactions in such solutions. How many grams of solute are in 1.75 L of 0.460 M sodium monohydrogen phosphate Plan We know the solution volume (1.75 L) and molarity (0.460 M), and we need the mass of solute. We use the known quantities to find the amount (mol) of solute and then convert moles to grams with the solute molar mass, as shown in the roadmap. 

H.RV Dihvdroj en phosphate ion HPOj - Monohydrogen phosphate ion 1-H" L5SX 10 ... 

Colorimetric Techniques The most familiar colorimetric technique is the molybdate blue method (Koch and Koch-Dedic 1964). Phosphate ion (P04 ), when in solution, reacts with a molybdate ion to form a heteropoly acid complex, H7[P(Mo207)5], that after use of suitable reduction agent is reduced to a phosphoro-molybdate blue complex, with an absorption maximum at 820-830 nm. The most popular reduction agents are chlorostannous (tin II dichloride) acid reductant, sodium bisulfite (monosodium, monohydrogen sulfate (IV)) and ascorbic acid. 

Hydroxylapatite is the stable orthophosphate of calcium in neutral and alkaline media. Its preparation in pure form is difficult, since with the customary precipitation reaction the monohydrogen phosphate ion always forms according to the reaction ... 

The results are different when 99.0 mL of buffer solution is used instead of pure water. A solution that contains the monohydrogen phosphate and dihydrogen phosphate ions, HPOf and H2PO4, in suitable proportions can serve as such a buffer. The Henderson-Hasselbalch equation can be used to calculate the HPO /H2PO4 ratio that corresponds to pH 7.0. 

Ka for HP04 is 4.8 x 10 Note that HP04 is the conjngate base of H2PO4, so Kb is 1.6 x 10 Comparing the two A s, we conclnde that the monohydrogen phosphate ion is a much stronger proton acceptor (base) than a proton donor (acid). The solntion will be basic. 

C3H7NH2 (b) monohydrogen phosphate ion, HP04 (c) benzoate ion, C6H5CO2 . 

Write the chemical equation and the JCj expression for the reaction of each of the following bases with water (a) propylamine, C3H7NH2 (b) monohydrogen phosphate ion, HP04 (c) benzoate ion, CgH5C02. ... 

Amphoteric species may also act as buffers by reacting with an acid or a base. (For an example of an amphoteric species, see "Make up your mind Amphoteric water, earlier in this chapter) The bicarbonate ion (HCO3 ) and the monohydrogen phosphate ion (HP04 ) are amphoteric species... 

As in (i) above, the carbonic anhydrase reaction forms protons (H+) and the new HCO3 " is secreted into the peritubuiar piasma. This time, the protons (H ) associate with monohydrogen phosphate ions (HF04 ) to form dihydrogen phosphate (H2P04") which is excreted in the urine... 

An example of this can be found in solutions for parenteral nutrition that contain calcium and phosphate ions (see Sect. 13.9.2). At the pH of parenteral nutrition mixtures dihydrogen phosphate and monohydrogen phosphate will both be present. The solubility of calcium dihydrogen... 

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