Potassium chromate

Names
IUPAC name

Potassium chromate

Other names

Chromic acid, (K2CrO4), dipotassium salt

Identifiers

CAS Number

* 7789-00-6 Y

3D model (JSmol)

* Interactive image

ChEBI |

* CHEBI:75249 N

ChemSpider |

* 22999 N

EC Number |

* 232-140-5

PubChem CID

* 24597

RTECS number |

* GB2940000

UNII |

* 5P0R38CN2X Y

InChI

* InChI=1S/Cr.2K.4O/q;2*+1;;;2*-1 N

Key: XMXNVYPJWBTAHN-UHFFFAOYSA-N N

* InChI=K2CrO4

Key: XMXNVYPJWBTAHN-QALQIXLOAU

SMILES

* [O-][Cr](=O)(=O)[O-].[K+].[K+]

Properties

Chemical formula

| K2CrO4
Molar mass | 194.189 g·mol−1
Appearance  | Yellow powder
Odor | odorless
Density | 2.7320 g/cm3
Melting point |  968 °C (1,774 °F; 1,241 K)
Boiling point |  1,000 °C (1,830 °F; 1,270 K)

Solubility in water

| 62.9 g/100 mL (20 °C)

75.1 g/100 mL (80 °C)
79.2 g/100 mL (100 °C)
Solubility | insoluble in alcohol

Magnetic susceptibility (χ)

| −3.9·10−6 cm3/mol

Refractive index (nD)

| 1.74
Structure

Crystal structure

| rhombic
Hazards
Safety data sheet | Chemical Safety Data

GHS hazard statements

| HH315Script error: No such module "Preview warning".Category:GHS errors, HH317Script error: No such module "Preview warning".Category:GHS errors, HH319Script error: No such module "Preview warning".Category:GHS errors, HH335Script error: No such module "Preview warning".Category:GHS errors, HH340Script error: No such module "Preview warning".Category:GHS errors, HH350iScript error: No such module "Preview warning".Category:GHS errors, HH410Script error: No such module "Preview warning".Category:GHS errors
NFPA 704 (fire diamond)  |

Related compounds

Other anions

| Potassium dichromate
Potassium molybdate
Potassium tungstate

Other cations

| Sodium chromate
Calcium chromate
Barium chromate

Related chromates

| Potassium hypochromate
Potassium perchromate

Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

N verify (what is YN ?)
Infobox references

Potassium chromate is the inorganic compound with the formula K2CrO4. This yellow solid is the potassium salt of the chromate anion. It is a common laboratory chemical, whereas sodium chromate is important industrially.

## Contents

* 1 Structure
* 2 Production and reactions
* 3 Applications
* 4 Occurrence
* 5 Safety
* 6 References

## Structure

Two crystalline forms are known, both being very similar to the corresponding potassium sulfate. Orthorhombic β-K2CrO4 is the common form, but it converts to an α-form above 66 °C.[1] These structures are complex, although the chromate ion adopts the typical tetrahedral geometry.[2]

* Structure of β-K2CrO4.

* Coordination sphere of one of two types of K+ site.

* The environment about the tetrahedral CrO42− center in β-K2CrO4.

## Production and reactions

It is prepared by treating potassium dichromate with potassium hydroxide:

[math]\ce{ K2Cr2O7(aq) + 2KOH -> 2K2CrO4 + H2O }[/math]

Or, the fusion of potassium hydroxide and chromium trioxide:

[math]\ce{ 2KOH + CrO3 -> K2CrO4 + H2O }[/math]

In solution, the behavior of potassium and sodium dichromates are very similar. When treated with lead(II) nitrate, it gives an orange-yellow precipitate, lead(II) chromate.

## Applications

Unlike the less expensive sodium salt, potassium salt is mainly used for laboratory work in situations where an anhydrous salt is required.[1] It is as an oxidizing agent in organic synthesis. It is used in qualitative inorganic analysis, e.g. as a colorimetric test for silver ion. It is also used as an indicator in precipitation titrations with silver nitrate and sodium chloride (they can be used as standard as well as titrant for each other) as potassium chromate turns red in the presence of excess of silver ions.

## Occurrence

Tarapacaite is the natural, mineral form of potassium chromate. It occurs very rarely and until now is known from only few localities on Atacama Desert.[citation needed]

## Safety

As with other Cr(VI) compounds, potassium chromate is carcinogenic.[3] The compound is also corrosive and exposure may produce severe eye damage or blindness.[4] Human exposure further encompasses impaired fertility, heritable genetic damage and harm to unborn children.

## References

1. ↑ 1.0 1.1 Gerd Anger, Jost Halstenberg, Klaus Hochgeschwender, Christoph Scherhag, Ulrich Korallus, Herbert Knopf, Peter Schmidt, Manfred Ohlinger, "Chromium Compounds" in Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim, 2005. doi:10.1002/14356007.a07_067
2. ↑ Gaultier, M.; Pannetier, G. "Structure cristalline de la forme 'basse temperature' du sulfate de potassium K2SO4-beta" (Crystal structure of the "low temperature" β-form of potassium sulfate) Bulletin de la Société Chimique de France 1968, vol. 1, pp. 105-12.
3. ↑ IARC (2012). Volume 100C: Arsenic, Metals, Fibres, and Dusts. Lyon: International Agency for Research on Cancer. ISBN 978-92-832-0135-9. https://publications.iarc.fr/_publications/media/download/3026/50ed50733f7d1152d91b30a803619022ef098d59.pdf. Retrieved 2020-01-05. "There is sufficient evidence in humans for the carcinogenicity of chromium (VI) compounds. Chromium (VI) compounds cause cancer of the lung. Also positive associations have been observed between exposure to Chromium (VI) compounds and cancer of the nose and nasal sinuses. There is sufficient evidence in experimental animals for the carcinogenicity of chromium (VI) compounds. Chromium (VI) compounds are carcinogenic to humans (Group 1)."
4. ↑ "Potassium dichromate MSDS". JT Baker. http://hazard.com/msds/mf/baker/baker/files/p5719.htm.

* v
* t
* e

Potassium compounds

* KAsO2
* KBr
* KBrO3
* KCN
* KCNO
* KCl
* KClO
* KClO3
* KClO4
* KF
* KH
* KHCO2
* KHCO3
* KHF2
* KHS
* KHSO3
* KHSO4
* KH2AsO4
* KH2PO3
* KH2PO4
* KI
* KIO3
* KIO4
* KMnO4
* KNH2
* KN3
* K3N
* KNO2
* KNO3
* KOCN
* KOH
* KO2
* KPF6
* KSCN
* KCH3COO
* K2Al2O4
* K2CO3
* K2CrO4
* K2Cr2O7
* K2FeO4
* K2HPO4
* K2MnO4
* K2O
* K2O2
* K2PtCl4
* K2PtCl6
* K2S
* K2SeO4
* K2SO3
* K2SO4
* KHSO5
* K2S2O5
* K2S2O7
* K2S2O8
* K2Po
* K2SiO3
* K3[Fe(CN)6]
* K3[Fe(C2O4)3]
* K4[Fe(CN)6]
* K3PO4
* K4Mo2Cl8

0.00

(0 votes)

Original source: https://en.wikipedia.org/wiki/Potassium chromate. Read more

|

Retrieved from "https://handwiki.org/wiki/index.php?title=Chemistry:Potassium_chromate&oldid=3334184"
*[CID]: Compound ID
*[v]: View this template
*[t]: Discuss this template
*[e]: Edit this template