Appearance white crystals Molar mass 146.43 g/mol Density 4.79 g/cm³ | Formula Cd(OH)2 Melting point 130 °C Boiling point 300 °C | |
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Cadmium hydroxide is an inorganic compound with the formula Cd(OH)2. It is a white crystalline ionic compound that is a key component of NiCd batteries.
Contents
Structure, preparation, and reactions
Cadmium hydroxide adopts the same structure as Mg(OH)2, consisting of slabs of octahedral metal centers surrounded by octahedral of hydroxide ligands.
It is produced by treating cadmium nitrate with sodium hydroxide:
Cd(NO3)2 + 2 NaOH → Cd(OH)2 + 2 NaNO3Attempted preparation from other cadmium salts is more complicated.
Cd(OH)2 and cadmium oxide react equivalently. Cadmium hydroxide is more basic than zinc hydroxide. It forms the anionic complex Cd(OH)42− when treated with concentrated caustic soda solution. It forms complexes with cyanide, thiocyanate and ammonium ions when added to the solutions of these ions. Cadmium hydroxide loses water on heating, producing cadmium oxide. Decomposition commences at 130 °C and is complete at 300 °C. Reactions with mineral acids (HX) produce the corresponding cadmium salts (CdX2). With hydrochloric acid, sulfuric acid and nitric acid, the products are cadmium chloride, cadmium sulfate and cadmium nitrate, respectively.
Uses
It is generated in storage battery anodes, in nickel-cadmium and silver-cadmium storage batteries in its discharge:
2 NiO(OH) + 2 H2O + Cd → Cd(OH)2 + Ni(OH)2