Zinc bromide (
Zn Br2) is an
inorganic compound
In chemistry, an inorganic compound is typically a chemical compound that lacks carbon–hydrogen bonds, that is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as '' inorganic chemist ...
with the chemical formula
Zn Br2. It is a colourless salt that shares many properties with
zinc chloride
Zinc chloride is the name of inorganic chemical compounds with the formula ZnCl2 and its hydrates. Zinc chlorides, of which nine crystalline forms are known, are colorless or white, and are highly soluble in water. This salt is hygroscopic and ev ...
(ZnCl
2), namely a high solubility in water forming acidic solutions, and good solubility in organic solvents. It is
hygroscopic
Hygroscopy is the phenomenon of attracting and holding water molecules via either absorption or adsorption from the surrounding environment, which is usually at normal or room temperature. If water molecules become suspended among the substance ...
and forms a dihydrate ZnBr
2·2H
2O.
Production
ZnBr
2 · 2H
2O is prepared by treating zinc oxide or zinc metal with
hydrobromic acid
Hydrobromic acid is a strong acid formed by dissolving the diatomic molecule hydrogen bromide (HBr) in water. "Constant boiling" hydrobromic acid is an aqueous solution that distills at and contains 47.6% HBr by mass, which is 8.77 mol/L. H ...
.
: ZnO + 2HBr + H
2O → ZnBr
2·2H
2O
: Zn + 2HBr → ZnBr
2 + H
2
The anhydrous material can be produced by dehydration of the dihydrate with hot CO
2 or by reaction of zinc metal and bromine.
Sublimation in a stream of hydrogen bromide also gives the anhydrous derivative.
[
]
Structure
ZnBr2 crystallizes in the same structure as ZnI2: four tetrahedral Zn centers share three vertices to form “super-tetrahedra” of nominal composition 2−, which are linked by their vertices to form a three-dimensional structure. The dihydrate ZnBr2 · 2H2O can be described as ( n(H2O)6sup>2+)2( n2Br6sup>2-).
Gaseous ZnBr2 is linear in accordance with VSEPR
Valence shell electron pair repulsion (VSEPR) theory ( , ), is a model used in chemistry to predict the geometry of individual molecules from the number of electron pairs surrounding their central atoms. It is also named the Gillespie-Nyholm theo ..