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Ammonium chromate

Ammonium chromate

Last updated: March 19, 2023

Ammonium chromate is an inorganic compound with formula (NH₄)₂CrO₄.

Table of contents

Names

List of substance names

Nomenclature

Name

Typical name: Ammonium chromate

Compositional nomenclature: Ammonium chromate; Diammonium chromate

Substitutive nomenclature: Azanium chromate

Additive nomenclature: Tetrahydridonitrogen(1+) tetraoxidochromate(2−)

Formulae and structures

List of formulae

Formula name

Formula

Typical formula: (NH₄)₂CrO₄

Compositional formula: (NH₄)₂CrO₄

Structural formula

Other structural formulas

Lewis structure

Colored Lewis structure

Properties

List of substance properties

Item

Value

Name: Ammonium chromate

Formula: (NH₄)₂CrO₄

Appearance: Yellow solid

Odor: Odorless

Molar mass: 152.070 g/mol

Density: 1.91 g/cm³^[1]
Solid, 12°C

Melting point: 185 °C^[1]
Decompose → (NH₄)₂Cr₂O₇, NH₃, H₂O

Boiling point: –

Constituents

Constituent ions

Ion	Name	Charge number	Number
NH₄⁺	Ammonium ion	1	2
CrO₄²⁻	Chromate ion	-2	1

Constituent atoms

Atom	Name	Oxidation state	Number
N	Nitrogen	−3	2
H	Hydrogen	+1	8
Cr	Chromium	+6	1
O	Oxygen	−2	4

Ratio of atoms

Atom	Atomic weight	Number	Atomic ratio	Weight ratio
N	14.007	2	13.33%	18.42%
H	1.008	8	53.33%	5.30%
Cr	51.9961	1	6.67%	34.19%
O	15.999	4	26.67%	42.08%

Thermodynamic properties

Phase transition properties

Item

Value

Enthalpy of fusion: –

Enthalpy of vaporization: –

Enthalpy of vaporization at 25°C: –

Enthalpy of other transition: –

Standard thermodynamic properties

State	Standard enthalpy of formation Δ_fH° kJ · mol⁻¹	Standard Gibbs energy of formation Δ_fG° kJ · mol⁻¹	Standard molar entropy S° J · K⁻¹ · mol⁻¹	Standard molar heat capacity at constant pressure C_p° J · K⁻¹ · mol⁻¹
Crystalline solid	−1167.3^[2]	–	–	–
Ionized aqueous solution	−1146.16^[2]	−886.36^[2]	277.0^[2]	–

Solubility

Qualitative solubility

Reactive

Miscible

Very soluble: H₂OWater

Soluble

Slightly soluble: CH₃OH^[1]Methanol

Very slightly soluble

Insoluble

Solubility in water (g/100 g)^[3]

0°C	10°C	20°C	30°C	40°C	60°C	80°C
25	29.2	34	39.3	45.3	59	76.1

Solubility curve (g/100 g)

Preparations

Reaction of acid and base

The reaction of chromic acid and ammonia yields ammonium chromate.

Reaction of chromic acid and ammonia: H₂CrO₄Chromic acid + 2NH₃Ammonia
⟶
(NH₄)₂CrO₄Ammonium chromate

Reaction of base, acidic oxide, and water

The reaction of ammonia, chromium(VI) oxide, and water yields ammonium chromate.

Reaction of ammonia, chromium(VI) oxide, and water: 2NH₃Ammonia + CrO₃Chromium(VI) oxide + H₂OWater
⟶
(NH₄)₂CrO₄Ammonium chromate

Chemical reactions

Electrolytic dissociation

Electrolytic dissociation of ammonium chromate yields ammonium ion and chromate ion.

Electrolytic dissociation of ammonium chromate: (NH₄)₂CrO₄Ammonium chromate
⟶
2NH₄⁺Ammonium ion + CrO₄²⁻Chromate ion

Reaction with reducing species

The reaction of reducing species and ammonium chromate yields a variety of products.

Reaction of hydrogen and ammonium chromate ◆ Δ_rG −147.9 kJ/mol K 8.15 × 10²⁵ pK −25.91: 3H₂Hydrogen + (NH₄)₂CrO₄Ammonium chromate
⟶
CrChromium + 2NH₃Ammonia + 4H₂OWater

Reaction of sodium and ammonium chromate ◆ Δ_rG −398.12 kJ/mol K 5.59 × 10⁶⁹ pK −69.75: 2NaSodium + (NH₄)₂CrO₄Ammonium chromate
⟶
Na₂CrO₄Sodium chromate + 2NH₃↑Ammonia + H₂↑Hydrogen

Reaction of hydrogen and ammonium chromate ◆ Δ_rG −589.6 kJ/mol K 1.97 × 10¹⁰³ pK −103.29: 3H₂Hydrogen + 2(NH₄)₂CrO₄Ammonium chromate
⟶
Cr₂O₃Chromium(III) oxide + 4NH₃Ammonia + 5H₂OWater

Reaction of sodium and ammonium chromate ◆ Δ_rG −648.38 kJ/mol K 3.90 × 10¹¹³ pK −113.59: 8NaSodium + (NH₄)₂CrO₄Ammonium chromate
⟶
4Na₂OSodium oxide + CrChromium + 2NH₃↑Ammonia + H₂↑Hydrogen

Reaction of hydrogen sulfide and ammonium chromate ◆ Δ_rG −23.4 kJ/mol K 1.26 × 10⁴ pK −4.10: 4H₂SHydrogen sulfide + (NH₄)₂CrO₄Ammonium chromate
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⟶
3SSulfur + CrChromium + (NH₄)₂SAmmonium sulfide + 4H₂OWater

Reaction with reducible species

The reaction of ammonium chromate and reducible species yields a variety of products.

Reaction of ammonium chromate and iodine: (NH₄)₂CrO₄Ammonium chromate + I₂Iodine
⟶
N₂H₄Hydrazine + 2HI↑Hydrogen iodide + H₂CrO₄Chromic acid

Reaction of ammonium chromate and iodine: 8(NH₄)₂CrO₄Ammonium chromate + 7I₂Iodine
⟶
2NO₂↑Nitrogen dioxide + 14NH₄IAmmonium iodide + 4H₂Cr₂O₇Dichromic acid

Reaction with oxidizable species

The reaction of oxidizable species and ammonium chromate yields a variety of products.

Reaction of copper and ammonium chromate ◆ Δ_rG 0.3 kJ/mol K 0.89 × 10⁰ pK 0.05: 5CuCopper + 2(NH₄)₂CrO₄Ammonium chromate
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⟶
5CuOCopper(II) oxide + Cr₂O₃Chromium(III) oxide + 4NH₃↑Ammonia + 2H₂↑Hydrogen

Reaction of copper and ammonium chromate ◆ Δ_rG −81.2 kJ/mol K 1.68 × 10¹⁴ pK −14.23: 10CuCopper + 2(NH₄)₂CrO₄Ammonium chromate
⟶
5Cu₂OCopper(I) oxide + Cr₂O₃Chromium(III) oxide + 4NH₃↑Ammonia + 2H₂↑Hydrogen

Reaction of iron(II) oxide and ammonium chromate: 8FeOIron(II) oxide + (NH₄)₂CrO₄Ammonium chromate
⟶
4Fe₂O₃Iron(III) oxide + CrChromium + 2NH₃↑Ammonia + H₂↑Hydrogen

Reaction of iron(II) oxide and ammonium chromate: 9FeOIron(II) oxide + (NH₄)₂CrO₄Ammonium chromate
⟶
3Fe₃O₄Iron(II,III) oxide + CrChromium + H₂OWater + 2NH₃↑Ammonia

Reaction with oxidizable species under acidic condition

The reaction of oxidizable species, ammonium chromate, and hydrogen ion yields a variety of products.

Reaction of copper and ammonium chromate under acidic condition: 3CuCopper + 2(NH₄)₂CrO₄Ammonium chromate + 16H⁺Hydrogen ion
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⟶
3Cu²⁺Copper(II) ion + 2Cr³⁺Chromium(III) ion + 4NH₄⁺Ammonium ion + 8H₂OWater

Reaction of copper and ammonium chromate under acidic condition: 3CuCopper + (NH₄)₂CrO₄Ammonium chromate + 8H⁺Hydrogen ion
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⟶
3Cu⁺Copper(I) ion + Cr³⁺Chromium(III) ion + 2NH₄⁺Ammonium ion + 4H₂OWater