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Phosphoric acid (orthophosphoric acid, monophosphoric acid or phosphoric(V) acid) is a colorless, odorless phosphorus-containing solid, and inorganic compound with the chemical formula H 3 P O 4. It is commonly encountered as an 85% aqueous solution , which is a colourless, odourless, and non- volatile syrupy liquid.
The general formula of a phosphoric acid is H n−2x+2 P n O 3n−x+1, where n is the number of phosphorus atoms and x is the number of fundamental cycles in the molecule's structure; that is, the minimum number of bonds that would have to be broken to eliminate all cycles.
The standard enthalpy change can be determined by calorimetry or by using the van 't Hoff equation, though the calorimetric method is preferable. When both the standard enthalpy change and acid dissociation constant have been determined, the standard entropy change is easily calculated from the equation above.
Hypophosphoric acid can be prepared by the reaction of red phosphorus with sodium chlorite at room temperature. [2]2 P + 2 NaClO 2 + 2 H 2 O → Na 2 H 2 P 2 O 6 + 2 HCl. A mixture of hypophosphoric acid, phosphorous acid (H 3 PO 3) and phosphoric acid (H 3 PO 4) is produced when white phosphorus oxidises in air when partially immersed in water.
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The reaction of an acid in water solvent is often described as a dissociation + + where HA is a proton acid such as acetic acid, CH 3 COOH. The double arrow means that this is an equilibrium process, with dissociation and recombination occurring at the same time.
The formula for this acid is generally written H 3 PO 2, but a more descriptive presentation is HOP(O)H 2, which highlights its monoprotic character. Salts derived from this acid are called hypophosphites. [3] HOP(O)H 2 exists in equilibrium with the minor tautomer HP(OH) 2. Sometimes the minor tautomer is called hypophosphorous acid and the ...
In thermodynamics, an activity coefficient is a factor used to account for deviation of a mixture of chemical substances from ideal behaviour. [1] In an ideal mixture, the microscopic interactions between each pair of chemical species are the same (or macroscopically equivalent, the enthalpy change of solution and volume variation in mixing is zero) and, as a result, properties of the mixtures ...