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Sodium selenate

Sodium selenate

Last updated: March 19, 2023

Sodium selenate is an inorganic compound with formula Na₂SeO₄.

Table of contents

Names

List of substance names

Nomenclature

Name

Typical name: Sodium selenate

Compositional nomenclature: Sodium selenate

Additive nomenclature: Sodium tetraoxidoselenate(2−)

Formulae and structures

List of formulae

Formula name

Formula

Typical formula: Na₂SeO₄

Compositional formula: Na₂SeO₄

Structural formula

Other structural formulas

Lewis structure

Colored Lewis structure

Properties

List of substance properties

Item

Value

Name: Sodium selenate

Formula: Na₂SeO₄

Appearance: Colorless solid

Odor: Odorless

Molar mass: 188.947 g/mol

Density: 3.098 g/cm³^[1]
Solid

Melting point: –

Boiling point: –

Constituents

Constituent ions

Ion	Name	Charge number	Number
Na⁺	Sodium ion	1	2
SeO₄²⁻	Selenate ion	-2	1

Constituent atoms

Atom	Name	Oxidation state	Number
Na	Sodium	+1	2
Se	Selenium	+6	1
O	Oxygen	−2	4

Ratio of atoms

Atom	Atomic weight	Number	Atomic ratio	Weight ratio
Na	22.990	2	28.57%	24.33%
Se	78.971	1	14.29%	41.80%
O	15.999	4	57.14%	33.87%

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	−1069.0^[2]	–	–	–
Ionized aqueous solution	−1079.5^[2]	−965.2^[2]	172.0^[2]	–
Crystalline solid 10 hydrate	−4006.6^[2]	–	–	–

Solubility

Qualitative solubility

Reactive

Miscible

Very soluble: H₂OWater

Soluble

Slightly soluble

Very slightly soluble

Insoluble

Solubility in water (g/100 g)^[1]

0°C	10°C	20°C	30°C	40°C	60°C	80°C	90°C	100°C
13.3	25.2	26.9	77	81.8	78.6	74.8	73	72.7

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

0°C	15°C	18°C	25.2°C	27°C	30°C	35.2°C	39.5°C	50°C	75°C	100°C
11.74	25.01	29	36.91	39.18	44.05	45.47	45.26	44.49	42.83	42.14

Solubility curve (g/100 g)

Solubility curve (g/100 g solution)

Hazards

GHS label^[4]

Item

Value

Hazard pictograms: GHS08: Health hazard; GHS09: Environment

Signal word: Danger

Hazard statements: H341: Suspected of causing genetic defects; H361: Suspected of damaging fertility or the unborn child; H372: Causes damage to organs through prolonged or repeated exposure; H372: Causes damage to skin through prolonged or repeated exposure; H372: Causes damage to tooth through prolonged or repeated exposure; H372: Causes damage to central nervous system through prolonged or repeated exposure; H372: Causes damage to liver through prolonged or repeated exposure; H372: Causes damage to kidney through prolonged or repeated exposure; H372: Causes damage to bone through prolonged or repeated exposure; H400: Very toxic to aquatic life; H410: Very toxic to aquatic life with long lasting effects

Physical hazards^[4]

Classification	Category	Label	Hazard statement
Explosives	Not applicable
Flammable gases	Not applicable
Aerosols	Not applicable
Oxidizing gases	Not applicable
Gases under pressure	Not applicable
Flammable liquids	Not applicable
Flammable solids	Not classified
Self reactive substances and mixtures	Not applicable
Pyrophoric liquids	Not applicable
Pyrophoric solids	Not classified
Self heating substances and mixtures	Not classified
Substances and mixtures which in contact with water emit flammable gases	Not classified
Oxidizing liquids	Not applicable
Oxidizing solids	Classification not possible
Organic peroxides	Not applicable
Substances and mixtures corrosive to metals	Classification not possible
Desensitized explosives	No data

Health hazards^[4]

Classification	Category	Label	Hazard statement
Acute oral toxicity	Classification not possible
Acute dermal toxicity	Classification not possible
Acute inhalation toxicity by gas	Not applicable
Acute inhalation toxicity by vapor	Not applicable
Acute inhalation toxicity by dust or mist	Classification not possible
Skin corrosion irritation	Classification not possible
Serious eye damage eye irritation	Classification not possible
Respiratory sensitization	Classification not possible
Skin sensitization	Classification not possible
Germ cell mutagenicity	Category 2	Warning	H341: Suspected of causing genetic defects
Carcinogenicity	Classification not possible
Reproductive toxicity	Category 2	Warning	H361: Suspected of damaging fertility or the unborn child
Specific target organ toxicity single exposure	Classification not possible
Specific target organ toxicity repeated exposure	Category 1 (Skin, Tooth, Central nervous system, Liver, Kidney, Bone)	Danger	H372: Causes damage to organs through prolonged or repeated exposure H372: Causes damage to skin through prolonged or repeated exposure H372: Causes damage to tooth through prolonged or repeated exposure H372: Causes damage to central nervous system through prolonged or repeated exposure H372: Causes damage to liver through prolonged or repeated exposure H372: Causes damage to kidney through prolonged or repeated exposure H372: Causes damage to bone through prolonged or repeated exposure
Aspiration hazard	Classification not possible

Environmental hazards^[4]

Classification	Category	Label	Hazard statement
Hazardous to the aquatic environment short term	Category 1	Warning	H400: Very toxic to aquatic life
Hazardous to the aquatic environment long term	Category 1	Warning	H410: Very toxic to aquatic life with long lasting effects
Hazardous to the ozone layer	Classification not possible

Preparations

Chemical reactions

Electrolytic dissociation

Electrolytic dissociation of sodium selenate yields sodium ion and selenate ion.

Electrolytic dissociation of sodium selenate: Na₂SeO₄Sodium selenate
⟶
2Na⁺Sodium ion + SeO₄²⁻Selenate ion

Reaction with dehydrating acid

The reaction of sodium selenate and dehydrating acid yields salt, selenium trioxide, and water.

Reaction of sodium selenate and sulfuric acid: Na₂SeO₄Sodium selenate + H₂SO₄Sulfuric acid
⟶
Na₂SO₄Sodium sulfate + SeO₃Selenium trioxide + H₂OWater

Reaction of sodium selenate and phosphoric acid: 3Na₂SeO₄Sodium selenate + 2H₃PO₄Phosphoric acid
⟶
2Na₃PO₄Sodium phosphate + 3SeO₃Selenium trioxide + 3H₂OWater

Reaction of sodium selenate and sulfuric acid: Na₂SeO₄Sodium selenate + 2H₂SO₄Sulfuric acid
⟶
2NaHSO₄Sodium hydrogensulfate + SeO₃Selenium trioxide + H₂OWater

Reaction of sodium selenate and phosphoric acid: Na₂SeO₄Sodium selenate + H₃PO₄Phosphoric acid
⟶
Na₂HPO₄Sodium hydrogenphosphate + SeO₃Selenium trioxide + H₂OWater

Reaction with reducing species

The reaction of reducing species and sodium selenate yields a variety of products.

Reaction of sodium and sodium selenate ◆ Δ_rG −536.6 kJ/mol K 1.02 × 10⁹⁴ pK −94.01: 6NaSodium + Na₂SeO₄Sodium selenate
⟶
4Na₂OSodium oxide + SeSelenium

Reaction of hydrogen and sodium selenate ◆ Δ_rG −448.3 kJ/mol K 3.46 × 10⁷⁸ pK −78.54: 4H₂Hydrogen + Na₂SeO₄Sodium selenate
⟶
Na₂SeSodium selenide + 4H₂OWater

Reaction of sodium and sodium selenate ◆ Δ_rG −931.2 kJ/mol K 1.38 × 10¹⁶³ pK −163.14: 8NaSodium + Na₂SeO₄Sodium selenate
⟶
Na₂SeSodium selenide + 4Na₂OSodium oxide

Reaction of hydrogen sulfide and sodium selenate ◆ Δ_rG −266.6 kJ/mol K 5.09 × 10⁴⁶ pK −46.71: 4H₂SHydrogen sulfide + Na₂SeO₄Sodium selenate
⟶
4SSulfur + Na₂SeSodium selenide + 4H₂OWater

Reaction of hydrogen sulfide and sodium selenate ◆ Δ_rG −328.1 kJ/mol K 3.02 × 10⁵⁷ pK −57.48: 4H₂SHydrogen sulfide + 3Na₂SeO₄Sodium selenate
⟶
4H₂SO₃Sulfurous acid + 3Na₂SeSodium selenide

Reaction with oxidizable species under acidic condition

The reaction of oxidizable species, sodium selenate, and hydrogen ion yields a variety of products.

Reaction of copper and sodium selenate under acidic condition ◆ Δ_rG −116.0 kJ/mol K 2.10 × 10²⁰ pK −20.32: 4CuCopper + Na₂SeO₄Sodium selenate + 8H⁺Hydrogen ion
⟶
4Cu²⁺Copper(II) ion + Na₂SeSodium selenide + 4H₂OWater

Reaction of copper and sodium selenate under acidic condition ◆ Δ_rG −310.7 kJ/mol K 2.71 × 10⁵⁴ pK −54.43: 3CuCopper + Na₂SeO₄Sodium selenate + 8H⁺Hydrogen ion
⟶
3Cu²⁺Copper(II) ion + SeSelenium + 2Na⁺Sodium ion + 4H₂OWater

Reaction of potassium iodide and sodium selenate under acidic condition ◆ Δ_rG −148.4 kJ/mol K 9.97 × 10²⁵ pK −26.00: 6KIPotassium iodide + Na₂SeO₄Sodium selenate + 8H⁺Hydrogen ion
⟶
6K⁺Potassium ion + 3I₂Iodine + SeSelenium + 2Na⁺Sodium ion + 4H₂OWater

Reaction of potassium iodide and sodium selenate under acidic condition ◆ Δ_rG −148.4 kJ/mol K 9.97 × 10²⁵ pK −26.00: 8KIPotassium iodide + Na₂SeO₄Sodium selenate + 8H⁺Hydrogen ion
⟶
8K⁺Potassium ion + 3I₂Iodine + SeSelenium + 2NaISodium iodide + 4H₂OWater

Reaction with oxidizable species

The reaction of oxidizable species and sodium selenate yields a variety of products.

Reaction of copper and sodium selenate ◆ Δ_rG −13.4 kJ/mol K 2.23 × 10² pK −2.35: 8CuCopper + Na₂SeO₄Sodium selenate
🔥
⟶
4Cu₂OCopper(I) oxide + Na₂SeSodium selenide

Reaction of copper and sodium selenate ◆ Δ_rG −58.2 kJ/mol K 1.57 × 10¹⁰ pK −10.20: CuCopper + Na₂SeO₄Sodium selenate
🔥
⟶
CuOCopper(II) oxide + Na₂SeO₃Sodium selenite

Reaction of iron(II) oxide and sodium selenate: 12FeOIron(II) oxide + Na₂SeO₄Sodium selenate
🔥
⟶
4Fe₃O₄Iron(II,III) oxide + Na₂SeSodium selenide

Reaction of iron(II) oxide and sodium selenate: 8FeOIron(II) oxide + Na₂SeO₄Sodium selenate
🔥
⟶
4Fe₂O₃Iron(III) oxide + Na₂SeSodium selenide

Reaction of potassium iodide and sodium selenate ◆ Δ_rG 2026.6 kJ/mol K 0.90 × 10⁻³⁵⁵ pK 355.04: 8KIPotassium iodide + Na₂SeO₄Sodium selenate
🔥
⟶
4K₂OPotassium oxide + 4I₂Iodine + Na₂SeSodium selenide

Reaction with hardly oxidizable species under acidic condition

The reaction of hardly oxidizable species, sodium selenate, and hydrogen ion yields a variety of products.

Reaction of hydrogen chloride and sodium selenate under acidic condition ◆ Δ_rG 280.2 kJ/mol K 0.81 × 10⁻⁴⁹ pK 49.09: 6HClHydrogen chloride + Na₂SeO₄Sodium selenate + 2H⁺Hydrogen ion
🔥
⟶
3Cl₂Chlorine + SeSelenium + 2Na⁺Sodium ion + 4H₂OWater

Reaction of sodium chloride and sodium selenate under acidic condition ◆ Δ_rG 280.2 kJ/mol K 0.81 × 10⁻⁴⁹ pK 49.09: 6NaClSodium chloride + Na₂SeO₄Sodium selenate + 8H⁺Hydrogen ion
🔥
⟶
8Na⁺Sodium ion + 3Cl₂↑Chlorine + SeSelenium + 4H₂OWater

Reaction of gold and sodium selenate under acidic condition: 2AuGold + Na₂SeO₄Sodium selenate + 8H⁺Hydrogen ion
🔥
⟶
2Au³⁺Gold(III) ion + SeSelenium + 2Na⁺Sodium ion + 4H₂OWater

Reaction of hydrogen chloride and sodium selenate under acidic condition: 2HClHydrogen chloride + Na₂SeO₄Sodium selenate + 2H⁺Hydrogen ion
⟶
Cl₂Chlorine + SeO₂Selenium dioxide + 2Na⁺Sodium ion + 2H₂OWater

Reaction of sodium chloride and sodium selenate under acidic condition: 2NaClSodium chloride + Na₂SeO₄Sodium selenate + 4H⁺Hydrogen ion
⟶
4Na⁺Sodium ion + Cl₂↑Chlorine + SeO₂Selenium dioxide + 2H₂OWater

Decomposition

Decomposition of sodium selenate yields sodium oxide and selenium trioxide.

Decomposition of sodium selenate ◆ Δ_rG 570.6 kJ/mol K 0.11 × 10⁻⁹⁹ pK 99.96: Na₂SeO₄Sodium selenate
🔥
⟶
Na₂SeSodium selenide + 2O₂↑Oxygen

Decomposition of sodium selenate ◆ Δ_rG 143.0 kJ/mol K 0.89 × 10⁻²⁵ pK 25.05: 2Na₂SeO₄Sodium selenate
🔥
⟶
2Na₂SeO₃Sodium selenite + O₂↑Oxygen

Decomposition of sodium selenate: Na₂SeO₄Sodium selenate
🔥
⟶
Na₂OSodium oxide + SeO₃Selenium trioxide

Electrolysis of aqueous solution

Electrolysis of aqueous sodium selenate yields a variety of products.

Electrolysis of water ◆ Δ_rG 474.258 kJ/mol K 0.82 × 10⁻⁸³ pK 83.09: 2H₂OWater
⚡
⟶
2H₂↑Hydrogen + O₂↑Oxygen

Electrolysis of aqueous sodium selenate without water as reactant ◆ Δ_rG 570.6 kJ/mol K 0.11 × 10⁻⁹⁹ pK 99.96: Na₂SeO₄Sodium selenate
💧⚡
⟶
Na₂SeSodium selenide + 2O₂↑Oxygen

Electrolysis of aqueous sodium selenate without water as reactant ◆ Δ_rG 143.0 kJ/mol K 0.89 × 10⁻²⁵ pK 25.05: 2Na₂SeO₄Sodium selenate
💧⚡
⟶
2Na₂SeO₃Sodium selenite + O₂↑Oxygen

Electrolysis of aqueous sodium selenate with water as non-redox agent ◆ Δ_rG 728.1 kJ/mol K 0.28 × 10⁻¹²⁷ pK 127.56: 2Na₂SeO₄Sodium selenate + 2H₂OWater
💧⚡
⟶
4NaOHSodium hydroxide + 2SeSelenium + 3O₂↑Oxygen

Electrolysis of aqueous sodium selenate with water as non-redox agent ◆ Δ_rG 174.6 kJ/mol K 0.26 × 10⁻³⁰ pK 30.59: Na₂SeO₄Sodium selenate + H₂OWater
💧⚡
⟶
Na₂SeO₃Sodium selenite + H₂O₂Hydrogen peroxide

References

List of references

1
James G. Speight (2017)
Lange's Handbook of Chemistry, 17th edition
https://www.accessengineeringlibrary.com/content/book/9781259586095
McGraw Hill Education
- Amazon
Citation list
- ^ Density, 3.098 g/cm³ - p.65
- ^ Solubility in Water (g/100 g), See the table - p.343
2
Janiel J. Reed (1989)
The NBS Tables of Chemical Thermodynamic Properties: Selected Values for Inorganic and C1 and C2 Organic Substances in SI Units
https://doi.org/10.18434/M32124
National Institute of Standards and Technology (NIST)
Citation list
3
Atherton Seidell (1919)
Solubilities of Inorganic and Organic Compounds: A Compilation of Quantitative Solubility Data From the Periodical Literature
D. Van Nostrand Company
- Amazon
Citation list
- ^ Solubility in Water (g/100 g solution), See the table - p.665
4
Chemical Management Center
GHS Classification Results
https://www.nite.go.jp/chem/english/ghs/all_fy_e.html
National Institute of Technology and Evaluation
Citation list

Δ_rG	255.7 kJ/mol
K	0.16 × 10⁻⁴⁴
pK	44.80

Δ_rG	284.6 kJ/mol
K	0.14 × 10⁻⁴⁹
pK	49.86

Δ_rG	375.2 kJ/mol
K	0.19 × 10⁻⁶⁵
pK	65.73

Δ_rG	−536.6 kJ/mol
K	1.02 × 10⁹⁴
pK	−94.01

Sodium selenate

Names

List of substance names

Formulae and structures

List of formulae

Properties

List of substance properties

Constituents

Constituent ions

Constituent atoms

Ratio of atoms

Thermodynamic properties

Phase transition properties

Standard thermodynamic properties

Solubility

Qualitative solubility

Solubility in water (g/100 g)[1]

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

Solubility curve (g/100 g)

Solubility curve (g/100 g solution)

Hazards

GHS label[4]

Physical hazards[4]

Health hazards[4]

Environmental hazards[4]

Preparations

Reaction of acid and base

Reaction of base and acidic oxide

Reaction of basic oxide and acid

Reaction of basic oxide and acidic oxide

Reaction of salt of weak acid and strong acid

Reaction of active metal and acid

Reaction of nonmetal and hydroxide base

Decomposition

Chemical reactions

Electrolytic dissociation

Reaction with dehydrating acid

Reaction with reducing species

Reaction with oxidizable species under acidic condition

Reaction with oxidizable species

Reaction with hardly oxidizable species under acidic condition

Decomposition

Electrolysis of aqueous solution

References

List of references

Related substances

Selenate of alkali metal

Selenium oxoacid salt of sodium

Acid and acidic oxide

Base and basic oxide

Related categories

Classification by constituent

Type of substance

State of substance

Property of substance

Solubility of substance

Color of substance

Odor of substance

Solubility in water (g/100 g)^[1]

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

GHS label^[4]

Physical hazards^[4]

Health hazards^[4]

Environmental hazards^[4]