Cadmium hydroxide
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| Names | |
|---|---|
| IUPAC name
Cadmium(II) hydroxide | |
| Identifiers | |
21041-95-2  | |
| 3D model (Jmol) | Interactive image |
| ChemSpider | 8488675 |
| ECHA InfoCard | 100.040.137 |
| PubChem | 10313210 |
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| Properties | |
| Cd(OH)2 | |
| Molar mass | 146.43 g/mol |
| Appearance | white crystals |
| Density | 4.79 g/cm3 |
| Melting point | 130 °C (266 °F; 403 K) |
| Boiling point | 300 °C (572 °F; 573 K) (decomposes) |
| 0.026 g/100 mL | |
| Solubility | soluble in dilute acids |
| Structure | |
| hexagonal | |
| Thermochemistry | |
| Std molar entropy (S |
96 J·mol−1·K−1[1] |
| Std enthalpy of formation (ΔfH |
−561 kJ·mol−1[1] |
| Hazards | |
| US health exposure limits (NIOSH): | |
| PEL (Permissible) |
[1910.1027] TWA 0.005 mg/m3 (as Cd)[2] |
| REL (Recommended) |
Ca[2] |
| IDLH (Immediate danger) |
Ca [9 mg/m3 (as Cd)][2] |
| Related compounds | |
| Other anions |
Cadmium chloride, Cadmium iodide |
| Other cations |
Zinc hydroxide, Calcium hydroxide, Magnesium hydroxide |
| Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). | |
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| Infobox references | |
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.[3]
Preparation and reactions
Cadmium hydroxide is produced by treating cadmium nitrate with sodium hydroxide:
- Cd(NO3)2 + 2 NaOH → Cd(OH)2 + 2 NaNO3
Attempted preparation from other cadmium salts is more complicated.[3] 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:
- 2NiO(OH) + 2H2O + Cd → Cd(OH)2 + Ni(OH)2
The hydroxide is used in place of cadmium oxide for variety of operations.
References
- 1 2 Zumdahl, Steven S. (2009). Chemical Principles 6th Ed. Houghton Mifflin Company. p. A21. ISBN 0-618-94690-X.
- 1 2 3 "NIOSH Pocket Guide to Chemical Hazards #0087". National Institute for Occupational Safety and Health (NIOSH).
- 1 2 Karl-Heinz Schulte-Schrepping, Magnus Piscator "Cadmium and Cadmium Compounds" in Ullmann's Encyclopedia of Industrial Chemistry, 2007 Wiley-VCH, Weinheim. doi:10.1002/14356007.a04_499.