Chemistry:Disodium hydrogen arsenate

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Disodium hydrogen arsenate
Na2HAsO4.svg
Names
IUPAC name
Disodium hydrogen arsorate
Other names
Sodium arsenate dibasic
Identifiers
ChEBI
EC Number
  • 231-902-4
UNII
Properties
H15Na2AsO11 (heptahydrate)
Molar mass 312.01 g/mol (heptahydrate)
Appearance white solid
good
Hazards
Main hazards poison
GHS pictograms GHS06: ToxicGHS08: Health hazardGHS09: Environmental hazard
GHS Signal word Danger
H301, H331, H350, H410
P201, P202, P261, P264, P270, P271, P273, P281, P301+310, P304+340, P308+313, P311, P321, P330, P391, P403+233, P405, P501
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references
Tracking categories (test):

Disodium hydrogen arsenate is the inorganic compound with the formula Na2HAsO4.7H2O. The compound consists of a salt and seven molecules of water of crystallization although for simplicity the formula usually omits the water component. The other sodium arsenates are NaH2AsO4 and Na3AsO4, the latter being called sodium arsenate. Disodium hydrogen arsenate is highly toxic. The salt is the conjugate base of arsenic acid. It is a white, water-soluble solid.[1]

Being a diprotic acid, its acid-base properties is described by two equilibria:

H2AsO4 + H2O ⇌ HAsO2−4 + H3O+  (pKa2 = 6.94)
HAsO2−4 + H2O ⇌ AsO3−4 + H3O+  (pKa3 = 11.5)

Related compounds

References