Potassium bromide

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Potassium bromide
Potassium bromide.jpg
Names
IUPAC name
Potassium bromide
Properties
KBr
Molar mass 119.002 g/mol
Appearance White solid
Odor Odorless
Density 2.74 g/cm3
Melting point 734 °C (1,353 °F; 1,007 K)
Boiling point 1,435 °C (2,615 °F; 1,708 K)
53.5 g/100 ml (0 °C)
67.8 g/100 ml (25 °C)
102 g/100 ml (100 °C)
Solubility Very slightly soluble in diethyl ether, methanol
Insoluble in hydrocarbons
Solubility in ethanol 4.76 g/100 ml (80 °C)
Solubility in glycerol 21.7 g/100 ml
Vapor pressure ~ 0 mmHg
Hazards
Safety data sheet Sigma-Aldrich
Flash point Non-flammable
Lethal dose or concentration (LD, LC):
3,070 mg/kg (rat, oral)
Related compounds
Related compounds
Potassium chloride
Potassium iodide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Potassium bromide (KBr) is a very stable and common bromide salt. It is commonly used to produce elemental bromine.

Properties

Chemical

Potassium bromide's properties are very similar to potassium chloride. The reaction with sulfuric acid produces hydrobromic acid, in the same way the chloride analogue produces hydrochloric acid.

However, bromine is not as strong an oxidizer as chlorine, so chlorine will form bromine if reacted with a solution of bromide.

2 KBr + Cl2 → 2 KCl + Br2

Bromide ions can be oxidized to bromate, which is a powerful oxidizer.

Physical

A white, nondescript solid, its density is high, and often samples are much heavier than what one subconsciously expects the crystalline white powder to weigh.

It dissolves quite easily to form a clear solution. If even small amounts of bromine is made in a reaction, the color of the solution shifts to a vivid orange as some bromine is somewhat soluble in a solution of bromide ions, forming the tribromide ion.

Potassium bromide, unusually, has covalent properties in the gas phase. It does, however, have one of the highest known dipole moments.

Availability

Potassium bromide is sometimes found as brominating tablets at pool stores as an alternative to chlorine. Other than this it is rarely found in consumer outlets but can be found easily and cheaply online or at any chemical supply store.

Preparation

Reacting elemental bromine with potassium hydroxide or potassium iodide will produce the potassium bromide salt:

KOH + Br2 → KBr + HOBr
KI + Br2 → KBr + I2

Hydrobromic acid can also be used instead of elemental bromine for the first reaction:

KOH + HBr → KBr + H2O

Projects

Handling

Safety

Bromide ions are a cumulative poison, staying in the blood for over a week. The only feasible routes of exposure are through purposefully consuming the solid or drinking solutions, neither of which is likely to occur, so it can be regarded as safe, provided high direct exposures to the body are limited.

Storage

Potassium bromide should be stored in closed containers.

Disposal

Can be safely poured down the drain.

References

http://en.m.wikipedia.org/wiki/Potassium_bromide (for toxicity data. Contains much more information about how your body deals with bromide ions)

Relevant Sciencemadness threads