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Sodium dihydrogen arsenate
Names
IUPAC name
Sodium dihydrogen arsorate
Other names
sodium arsenate monobasic, sodium dihydroarsenate
Identifiers
3D model ( JSmol)
PubChem CID
  • InChI=1S/AsH3O4.Na/c2-1(3,4)5;/h(H3,2,3,4,5);/q;+1/p-1
    Key: XCVRTGQHVBWRJB-UHFFFAOYSA-M
  • O[As](=O)(O)[O-].[Na+]
Properties
NaH4AsO5 (monohydrate)
Molar mass 181.9 g/mol
Appearance colourless solid
Density 2.53 g/cm3
slightly soluble
Hazards
Occupational safety and health (OHS/OSH):
Main hazards
toxic
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

Sodium dihydrogen arsenate is the inorganic compound with the formula NaH2AsO4. Related salts are also called sodium arsenate, including Na2HAsO4 ( disodium hydrogen arsenate) and NaH2AsO4 (sodium dihydrogen arsenate). Sodium dihydrogen arsenate is a colorless solid that is highly toxic.

The salt is the conjugate base of arsenic acid:

H3AsO4 ⇌ H2AsO
4
+ H+ (K1 = 10−2.19)

In the laboratory, it is prepared in this way, crystallizing from a hot saturated aqueous solution, where it is highly soluble when hot (75.3 g in 100 mL at 100 °C). It is obtained as the monohydrate.

Upon heating, solid NaH2AsO4H2O, loses water of crystallization and converts to the pyroarsenate salt Na2H2As2O7. [1]

References

  1. ^ Schenk, P. W. (1963). Brauer, G. (ed.). Arsenic, Antimony, Bismuth" in Handbook of Preparative Inorganic Chemistry. Vol. 1 (2nd ed.). New York: Academic Press. p. 602.