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H 2 AsO − 4 + H 2 O ⇌ HAsO 2− 4 + [H 3 O] +, pK a2 = 6.94 HAsO 2− 4 + H 2 O ⇌ AsO 3− 4 + [H 3 O] +, pK a3 = 11.5. These pK a values are close to those for phosphoric acid. The highly basic arsenate ion (AsO 3− 4) is the product of the third ionization. Unlike phosphoric acid, arsenic acid is an oxidizer, as illustrated by its ...
The biogeochemistry of arsenic is complex and includes various adsorption and desorption processes. The toxicity of arsenic is connected to its solubility and is affected by pH. Arsenite (AsO 3− 3) is more soluble than arsenate (AsO 3− 4) and is more toxic; however, at a lower pH, arsenate becomes more mobile and toxic. It was found that ...
Arsenic forms colorless, odorless, crystalline oxides As 2 O 3 ("white arsenic") and As 2 O 5 which are hygroscopic and readily soluble in water to form acidic solutions. Arsenic(V) acid is a weak acid and the salts are called arsenates , [ 5 ] the most common arsenic contamination of groundwater , and a problem that affects many people.
Trihydrogen arsenate is also known as arsenic acid. At a given pH, the distribution of these arsenate species can be determined from their respective acid dissociation constants. [17] H 3 AsO 4 + H 2 O ⇌ H 2 AsO − 4 + [H 3 O] + (pK a1 = 2.19) H 2 AsO − 4 + H 2 O ⇌ HAsO 2− 4 + [H 3 O] + (pK a2 = 6.94) HAsO 2− 4 + H 2 O ⇌ AsO 3− 4 ...
In its standard state arsine is a colorless, denser-than-air gas that is slightly soluble in water (2% at 20 °C) [1] and in many organic solvents as well. [citation needed] Arsine itself is odorless, [5] but it oxidizes in air and this creates a slight garlic or fish-like scent when the compound is present above 0.5 ppm. [6]
With its first pK a being 9.2, As(OH) 3 is a weak acid. [4] Reactions attributed to aqueous arsenic trioxide are due to arsenous acid and its conjugate bases. Like arsenic trioxide, arsenous acid is sometimes amphoteric. For example, it reacts with hydrochloric, hydrobromic, and hydroiodic acids to produce arsenic trichloride, tribromide, and ...
Arsenic-arsenic bonds are very weak, and oligomeric arsenic compounds are even more liable to oxidize than their hydrogenated precursors. [6]: 318–320 The following reaction can, however, be prepared through electrochemical reduction in a zinc-sulfate cell. [6]: 473 Oxidation first forms polymeric arsinoxides, e.g.: MeAs + O → MeAsO
2 Na 2 H[AsO 4] + 3 CaCl 2 → 4 NaCl + Ca 3 [AsO 4] 2 + 2 HCl. In the 1920s, it was made in large vats by mixing calcium oxide and arsenic oxide. [6] In the United States, 1360 metric tons were produced in 1919, 4540 in 1920, and 7270 in 1922. [1] The composition of commercially available calcium arsenate varies from manufacturer to manufacturer.