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Phosphorous acid (or phosphonic acid) is the compound described by the formula H 3 PO 3. This acid is diprotic (readily ionizes two protons), not triprotic as might be suggested by this formula. Phosphorous acid is an intermediate in the preparation of other phosphorus compounds.
Phosphoric acid units can be bonded together in rings (cyclic structures). The simplest such compound is trimetaphosphoric acid or cyclo-triphosphoric acid having the formula H 3 P 3 O 9. Its structure is shown in the illustration. Since the ends are condensed, its formula has one less H 2 O (water) than tripolyphosphoric acid.
For example, acetic acid is a weak acid which has a = 1.75 x 10 −5. Its conjugate base is the acetate ion with K b = 10 −14 /K a = 5.7 x 10 −10 (from the relationship K a × K b = 10 −14), which certainly does not correspond to a strong base. The conjugate of a weak acid is often a weak base and vice versa.
HPA is usually supplied as a 50% aqueous solution and heating at low temperatures (up to about 90 °C) prompts it to react with water to form phosphorous acid and hydrogen gas. H 3 PO 2 + H 2 O → H 3 PO 3 + H 2. Heating above 110 °C causes hypophosphorous acid to undergo disproportionation to give phosphorous acid and phosphine. [7] 3 H 3 PO ...
A weak acid may be defined as an acid with pK a greater than about −2. An acid with pK a = −2 would be 99 % dissociated at pH 0, that is, in a 1 M HCl solution. Any acid with a pK a less than about −2 is said to be a strong acid. Strong acids are said to be fully dissociated.
These acids, and their esters and salts ("phosphates") include some of the best-known and most important compounds of phosphorus. Orthophosphoric acid, H 3 PO 4. The simplest member of this class is: Phosphoric acid proper (also called orthophosphoric acid or monophosphoric acid), H 3 PO 4 (or OP(OH) 3), a triprotic acid.
In mathematics, a weak solution (also called a generalized solution) to an ordinary or partial differential equation is a function for which the derivatives may not all exist but which is nonetheless deemed to satisfy the equation in some precisely defined sense. There are many different definitions of weak solution, appropriate for different ...
The strength of a strong acid is limited ("leveled") by the basicity of the solvent. Similarly the strength of a strong base is leveled by the acidity of the solvent. When a strong acid is dissolved in water, it reacts with it to form hydronium ion (H 3 O +). [2] An example of this would be the following reaction, where "HA" is the strong acid: