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Potassium iodide

Chemical structure of potassium iodide

Potassium iodide is an inorganic compound with formula KI.

Table of contents
  1. 1Names
  2. 2Formulae and structures
  3. 3Properties
  4. 4Constituents
  5. 5Thermodynamic properties
  6. 6Solubility
  7. 7Hazards
  8. 8Preparations
  9. 9Chemical reactions
  10. 10References
  11. 11Related substances
  12. 12Related categories

Names

List of substance names

Nomenclature
Name
Typical name
Potassium iodide
Compositional nomenclature
Potassium iodide

Formulae and structures

List of formulae

Formula name
Formula
Typical formula
KI
Compositional formula
KI
Structural formula
Chemical structure of potassium iodide
Lewis structure
Lewis structure of potassium iodide
Colored Lewis structure
Colored Lewis structure of potassium iodide

Properties

List of substance properties

Item
Value
Name
Potassium iodide
Formula
KI
Appearance
Colorless solid
Odor
Odorless
Molar mass
166.00 g/mol
Density
3.12 g/cm3[1][2]
Solid
Melting point
681 °C[1][2]
Boiling point
1345 °C[1]
1323 °C[2]

Constituents

Constituent ions

IonNameCharge numberNumber
K+Potassium ion11
IIodide ion-11

Constituent atoms

AtomNameOxidation stateNumber
KPotassium+11
IIodine−11

Ratio of atoms

AtomAtomic weightNumberAtomic ratioWeight ratio
K39.0983150.00%23.55%
I126.90150.00%76.45%
KIAtomic ratio
KIWeight ratio

Thermodynamic properties

Phase transition properties

Item
Value
Enthalpy of fusion
24.0 kJ · mol−1[1][2]
at 681°C
Enthalpy of vaporization
190.9 kJ · mol−1[1]
at 1345°C
Enthalpy of vaporization at 25°C
202.4 kJ · mol−1[1]
Enthalpy of other transition

Standard thermodynamic properties

State
Standard enthalpy
of formation
ΔfH°
kJ · mol−1
Standard Gibbs
energy of
formation
ΔfG°
kJ · mol−1
Standard
molar entropy
S°
J · K−1 · mol−1
Standard molar
heat capacity at
constant pressure
Cp°
J · K−1 · mol−1
Crystalline solid−327.900[3]−324.892[3]106.32[3]52.93[3]
Gas−125.5[3]−166.1[3]258.3[3]37.11[3]
Ionized aqueous solution−307.57[3]−334.85[3]213.8[3]−120.5[3]

Solubility

Qualitative solubility

Reactive
Miscible
Very soluble
NH2OHHydroxylamine
C3H8O3Glycerol
Soluble
Slightly soluble
C5H5NPyridine
Very slightly soluble
Insoluble

Solubility in water (g/100 g)[4]

0°C10°C20°C30°C40°C60°C80°C90°C100°C
128136144153162176192198206

Solubility in water (g/100 g)[4]

-10°C-5°C-1°C0°C10°C20°C25°C30°C40°C50°C60°C70°C80°C90°C100°C110°C120°C
115.1119.8122.2127.5136144148152160168176184192200208215223

Solubility in hydroxylamine (g/100 g)[4]

17.5°C
110

Solubility in glycerol (g/100 g)[4]

15.5°C
40

Solubility in acetic acid (g/100 g, 95%)[4]

18.5°C
38.2

Solubility in methanol (g/100 g)[4]

11.4°C12.2°C13.5°C25°C
13.514.61618.04

Solubility in methanol (g/100 g)[4]

15°C30°C50°C80°C100°C120°C140°C160°C180°C200°C220°C240°C245°C247°C250°C252.5°C
14.516.218.922.52527.229.230.630.729.127.524.822.62113.87.6

Solubility in acetone (g/100 g)[4]

-2.5°C22°C25°C56°C
3.082.382.931.21

Solubility in ethanol (g/100 g)[4]

13.6°C25°C
1.632.16

Solubility in 1-propanol (g/100 g)[4]

12.2°C25°C
0.7310.43

Solubility in pyridine (g/100 g)[4]

10°C119°C
0.260.11

Solubility in 1-pentanol (g/100 g)[4]

25°C
0.098

Solubility in hydrazine (g/100 mL)[4]

20°C
175

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

20°C
144

Solubility in glycerol (g/100 mL)[1]

20°C
50

Solubility in ethanol (g/100 mL)[1]

20°C
4.5

Solubility curve (g/100 g)

0°C20°C40°C60°C80°C100°CTemperature (°C)050100150200250300Solubility (g/100 g)

Solubility curve (g/100 mL)

0°C20°C40°C60°C80°C100°CTemperature (°C)050100150200Solubility (g/100 mL)

Hazards

GHS label[5]

Physical hazards[5]

Health hazards[5]

Environmental hazards[5]

Preparations

Reaction of metal and nonmetal

The reaction of potassium and iodine yields potassium iodide.

Reaction of potassium and iodine
ΔrG−649.784 kJ/mol
K6.87 × 10113
pK−113.84

Reaction of acid and base

The reaction of hydrogen iodide and potassium hydroxide yields potassium iodide and water.

Reaction of basic oxide and acid

The reaction of potassium oxide and hydrogen iodide yields potassium iodide and water.

Reaction of salt of weak acid and strong acid

The reaction of salt of weak acid and strong acid can yield potassium iodide.

Reaction of salt of weak base and strong base

The reaction of salt of weak base and strong base can yield potassium iodide.

Reaction of active metal and acid

The reaction of potassium and hydrogen iodide yields potassium iodide and hydrogen.

Reaction of potassium and hydrogen iodide
ΔrG−653.18 kJ/mol
K2.71 × 10114
pK−114.43

Reaction of nonmetal and hydroxide base

The reaction of iodine and potassium hydroxide yields potassium iodate, potassium iodide, and water.

Decomposition

Decomposition of thermally decomposable substance can yield potassium iodide.

Decomposition of potassium iodate
ΔrG186.92 kJ/mol
K0.18 × 10−32
pK32.75
Decomposition of potassium iodate
ΔrG256.7 kJ/mol
K0.11 × 10−44
pK44.97

Chemical reactions

Electrolytic dissociation

Electrolytic dissociation of potassium iodide yields potassium ion and iodide ion.

Electrolytic dissociation of potassium iodide
ΔrG−9.95 kJ/mol
K5.54 × 101
pK−1.74
KIPotassium iodide
K+Potassium ion + IIodide ion

Reaction with nonvolatile acid

The reaction of potassium iodide and nonvolatile acid yields salt of non volatile acid and hydrogen iodide.

Reaction with oxidizing species

The reaction of potassium iodide and oxidizing species yields a variety of products.

Reaction of potassium iodide and oxygen
ΔrG−186.92 kJ/mol
K5.58 × 1032
pK−32.75
Reaction of potassium iodide and fluorine
ΔrG−425.72 kJ/mol
K3.83 × 1074
pK−74.58
Reaction of potassium iodide and bromine
ΔrG−111.54 kJ/mol
K3.48 × 1019
pK−19.54

Reaction with oxidizing species under acidic condition

The reaction of potassium iodide, oxidizing species, and hydrogen ion yields a variety of products.

Reaction of potassium iodide and oxygen under acidic condition
ΔrG−251.5 kJ/mol
K1.15 × 1044
pK−44.06
4KIPotassium iodide + O2Oxygen + 4H+Hydrogen ion
4K+Potassium ion + 2I2Iodine + 2H2OWater
Reaction of potassium iodide and iodic acid under acidic condition
ΔrG−271.7 kJ/mol
K3.98 × 1047
pK−47.60
5KIPotassium iodide + HIO3Iodic acid + 5H+Hydrogen ion
5K+Potassium ion + 3I2Iodine + 3H2OWater
Reaction of potassium iodide and potassium iodate under acidic condition
ΔrG−276.4 kJ/mol
K2.65 × 1048
pK−48.42
5KIPotassium iodide + KIO3Potassium iodate + 6H+Hydrogen ion
6K+Potassium ion + 3I2Iodine + 3H2OWater
Reaction of potassium iodide and sodium iodate under acidic condition
ΔrG−276.3 kJ/mol
K2.54 × 1048
pK−48.41
5KIPotassium iodide + NaIO3Sodium iodate + 6H+Hydrogen ion
5K+Potassium ion + 3I2Iodine + Na+Sodium ion + 3H2OWater
Reaction of potassium iodide and manganese(IV) oxide under acidic condition
ΔrG−117.7 kJ/mol
K4.17 × 1020
pK−20.62
2KIPotassium iodide + MnO2Manganese(IV) oxide + 4H+Hydrogen ion
2K+Potassium ion + I2Iodine + Mn2+Manganese(II) ion + 2H2OWater

Reaction with oxidizing species under neutral condition

The reaction of potassium iodide, oxidizing species, and water yields a variety of products.

Reaction of potassium iodide and fluorine under neutral condition
ΔrG−1021.3 kJ/mol
K8.39 × 10178
pK−178.92
Reaction of potassium iodide and sodium bromate under neutral condition
ΔrG−577.15 kJ/mol
K1.30 × 10101
pK−101.11

Reaction with reducible species

The reaction of potassium iodide and reducible species yields a variety of products.

Reaction with reducing species

The reaction of sodium and potassium iodide yields sodium iodide and potassium.

Reaction of sodium and potassium iodide
ΔrG38.83 kJ/mol
K0.16 × 10−6
pK6.80

Precipitation reaction

When a certain chemical species is present in aqueous solution, it reacts with potassium iodide to form a precipitate.

Electrolysis of aqueous solution

Electrolysis of aqueous potassium iodide yields a variety of products.

Electrolysis of aqueous potassium iodide with water as oxidizing agent
ΔrG365.88 kJ/mol
K0.80 × 10−64
pK64.10
Electrolysis of aqueous potassium iodide with water as oxidizing agent
ΔrG617.93 kJ/mol
K0.55 × 10−108
pK108.26
Electrolysis of water
ΔrG474.258 kJ/mol
K0.82 × 10−83
pK83.09

Molten salt electrolysis

Molten salt electrolysis of potassium iodide yields potassium and iodine.

Molten salt electrolysis of potassium iodide
ΔrG649.784 kJ/mol
K0.15 × 10−113
pK113.84

References

List of references

  1. 1
  2. 2
    John R. Rumble Jr, David R. Lide, Thomas J. Bruno (2019)
    CRC Handbook of Chemistry and Physics 100th Edition
    CRC Press

  3. 3
  4. 4
  5. 5