Monopotassium arsenate

Monopotassium arsenate
Names
	IUPAC name Potassium dihydrogen arsorate
	Other names Macquer's salt
Identifiers
CAS Number	7784-41-0 ;
3D model (JSmol)	Interactive image;
ChemSpider	22977;
ECHA InfoCard	100.029.150
EC Number	232-065-8;
PubChem CID	516881;
UNII	55K74GS94Q;
UN number	1677
CompTox Dashboard (EPA)	DTXSID9041100 ;
	InChI InChI=1S/AsH3O4.K/c2-1(3,4)5;/h(H3,2,3,4,5);/q;+1/p-1 Key: GVPLVOGUVQAPNJ-UHFFFAOYSA-M;
	SMILES O[As](=O)(O)[O-].[K+];
Properties
Chemical formula	AsH2KO4
Molar mass	180.032 g·mol−1
Appearance	white solid
Density	2.867 g/cm3
Melting point	288 °C (550 °F; 561 K)
Hazards
	GHS labelling:
Pictograms
Signal word	Danger
Hazard statements	H301, H331, H350, H410
Precautionary statements	P201, P202, P261, P264, P270, P271, P273, P281, P301+P310, P304+P340, P308+P313, P311, P321, P330, P391, P403+P233, P405, P501
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Monopotassium arsenate is the inorganic compound with the formula KH₂AsO₄. A white solid, this salt is used to prepared other arsenic-containing compounds, mainly pesticides. It is prepared by calcining arsenic oxide and potassium nitrate, followed by extraction with water.^[1]

Relevant acid-base equilibria for aqueous solutions of this diprotic acid derived from arsenic acid are as follows:

H₃AsO₄ + H₂O ⇌ H
₂AsO⁻
₄ + H₃O⁺ (pK_a1 = 2.19)

H
₂AsO⁻
₄ + H₂O ⇌ HAsO²⁻
₄ + H₃O⁺ (pK_a2 = 6.94)

^ Grund, S. C.; Hanusch, K.; Wolf, H. U. "Arsenic and Arsenic Compounds". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a03_113.pub2. ISBN 978-3527306732.{{cite encyclopedia}}: CS1 maint: multiple names: authors list (link)

[Ullmann-1] Grund, S. C.; Hanusch, K.; Wolf, H. U. "Arsenic and Arsenic Compounds". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a03_113.pub2. ISBN 978-3527306732.{{cite encyclopedia}}: CS1 maint: multiple names: authors list (link)

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