Formula ZnBr2 Melting point 394 °C Boiling point 697 °C | Molar mass 225.198 g/mol Density 4.2 g/cm³ | |
![]() | ||
Appearance white crystalline powder; hygroscopic Soluble in Alcohol, Acetone, Ether, Tetrahydrofuran |
Diy zinc bromide battery
Zinc bromide (ZnBr2) is an inorganic compound with the chemical formula ZnBr2. It is a colourless salt that shares many properties with zinc chloride (ZnCl2), namely a high solubility in water forming acidic solutions, and solubility in organic solvents. It is hygroscopic and forms a dihydrate ZnBr2 · 2H2O.
Contents
Calcium bromide and zinc bromide
Production
ZnBr2 · 2H2O is prepared by treating zinc oxide or zinc metal with hydrobromic acid.
ZnO + 2 HBr + H2O → ZnBr2 · 2H2OThe anhydrous material can be produced by dehydration of the dihydrate with hot CO2 or by reaction of zinc metal and bromine.
Structure
Crystalline ZnBr2 adopts the same structure as ZnI2: four tetrahedral Zn centers share three vertices to form “super-tetrahedra” of nominal composition {Zn4Br10}2−, which are linked by their vertices to form a three-dimensional structure. The dihydrate ZnBr2 · 2H2O also has a usual structure and should be described as Zn(H2O)6 Zn2Br6, where the Zn2Br62− ion has bromine bridges linking the two zinc atoms. A similar structure is found in the dimeric form of aluminium bromide (Al2Br6).
Gaseous ZnBr2 is linear in accordance with VSEPR theory with a Zn-Br bond length of 221 pm.
Uses
Zinc bromide is used in the following applications:
Safety
Safety considerations are similar to those for zinc chloride, for which the toxic dose for humans is 3–5 g.