Potassium bromate
| Names | |
|---|---|
| IUPAC name
Potassium bromate
| |
| Preferred IUPAC name
Potassium bromate | |
| Systematic IUPAC name
Potassium bromate | |
| Other names
E924
Potassium bromate(V) | |
| Properties | |
| KBrO3 | |
| Molar mass | 167.00 g/mol |
| Appearance | White solid |
| Odor | Odorless |
| Density | 3.27 g/cm3 |
| Melting point | 350 °C (662 °F; 623 K) |
| Boiling point | 370 °C (698 °F; 643 K) (decomposes) |
| 3.1 g/100 ml (0 °C) 6.91 g/100 ml (20 °C) 13.3 g/100 ml (40 °C) 49.7 g/100 ml (100 °C) | |
| Solubility | Insoluble in acetone, benzene, chloroform, diethyl ether |
| Vapor pressure | ~0 mmHg |
| Thermochemistry | |
| Std enthalpy of
formation (ΔfH |
-342.5 kJ/mol |
| Hazards | |
| Safety data sheet | Fisher Scientific |
| Flash point | Non-flammable |
| Lethal dose or concentration (LD, LC): | |
| LD50 (Median dose)
|
157 mg/kg (oral, rat) |
| Related compounds | |
| Related compounds
|
Sodium bromate |
| Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). | |
| Infobox references | |
Potassium bromate is an inorganic chemical compound with the formula KBrO3, the potassium salt of bromic acid.
Contents
Properties
Chemical
Addition of a strong acid, like conc. sulfuric acid to potassium bromate will yield bromic acid, which immediately decomposes to bromine, oxygen and water.
Potassium bromate decomposes when heated above 350 °C to potassium bromide and oxygen.
- KBrO3 → KBr + 3/2 O2
Addition of a mixture containing potassium bromate, cerium(IV) sulfate, malonic acid and citric acid, in dilute sulfuric acid, will cause the ratio of concentration of the cerium(IV) and cerium(III) ions to oscillate, causing the color of the solution to oscillate between a yellow solution and a colorless solution. This reaction is known as Belousov–Zhabotinsky reaction.
Physical
Potassium bromate is a white colorless solid, slightly soluble in water.
Availability
Potassium bromate is available as a flour improver (E number E924), and can be bought from industrial food suppliers. It is readily available in United States, as food grade.
Higher purity KBrO3 can be bought from chemical suppliers.
Preparation
Potassium bromate can be prepared by passing bromine through a hot solution of potassium hydroxide. This forms the unstable potassium hypobromite, which disproportionates into potassium bromide and potassium bromate.
- 2 KOH + Br2 → 2 KBrO + KBr + H2O
- 3 KBrO → KBrO3 + 2 KBr
Electrolysis of potassium bromide solutions will also give bromate. Both processes are analogous to those used in the production of chlorates.
Potassium bromate can be separated from the potassium bromide present in both methods very easy, owing to its much lower solubility: when a solution containing potassium bromate and bromide is cooled to 0 °C, nearly all bromate will precipitate, while nearly all of the bromide will stay in solution, due to KBr's high solubility at that temperature (53.5 g/100 ml).[1]
Projects
- Bake bread
- Belousov–Zhabotinsky reaction
- Oxidizing agent in some pyrotechnic mixtures
Handling
Safety
Potassium bromate is an oxidizer and should be handled with care.
Potassium bromate is classified as a category 2B carcinogen (possibly carcinogenic to humans) by the International Agency for Research on Cancer (IARC). Potassium bromate has been banned from use in food products in the European Union, Argentina, Brazil, Canada, Nigeria, South Korea, Peru, and some other countries, such as Sri Lanka, China and India.
Storage
In closed bottles, away from reducing agents.
Disposal
A reducing agent, such as sulfite or thiosulfate can be used to neutralize the compound to potassium bromide.
