Cadmium hydroxide
Chemical compound From Wikipedia, the free encyclopedia
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 nickel–cadmium battery.[5]
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| Names | |
|---|---|
| IUPAC name
Cadmium(II) hydroxide | |
| Identifiers | |
3D model (JSmol) |
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| ChemSpider | |
| ECHA InfoCard | 100.040.137 |
PubChem CID |
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| UNII | |
CompTox Dashboard (EPA) |
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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 product (Ksp) |
7.2×10−15 [1] |
| Solubility | soluble in dilute acids |
| Acidity (pKa) | 10[2] |
| −41.0·10−6 cm3/mol | |
| Structure | |
| hexagonal | |
| Thermochemistry | |
Std molar entropy (S⦵298) |
96 J·mol−1·K−1[3] |
Std enthalpy of formation (ΔfH⦵298) |
−561 kJ·mol−1[3] |
| Hazards | |
| NIOSH (US health exposure limits): | |
PEL (Permissible) |
[1910.1027] TWA 0.005 mg/m3 (as Cd)[4] |
REL (Recommended) |
Ca[4] |
IDLH (Immediate danger) |
Ca [9 mg/m3 (as Cd)][4] |
| 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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Structure
Cadmium hydroxide adopts the same structure as Mg(OH)2, consisting of slabs of metal centers, each bonded by six hydroxide ligands.[6] The Cd(OH)2 structure is a recurring motif in inorganic chemistry. For example it is adopted by vanadium ditelluride.[7]
Preparation, and reactions
Cadmium hydroxide is produced by treating an aqueous solution containing Cd2+ (say cadmium nitrate) with sodium hydroxide:[8][5]
- Cd(NO3)2 + 2 NaOH → Cd(OH)2 + 2 NaNO3
Cd(OH)2 and cadmium oxide exhibit similar reactions. Cadmium hydroxide is more basic than zinc hydroxide. It forms the anionic complex [Cd(OH)4]2− when treated with concentrated base. It forms complexes with cyanide, thiocyanate, and ammonia.
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) gives the corresponding cadmium salts (CdX2). With hydrochloric acid, sulfuric acid, and nitric acid, the products are cadmium chloride, cadmium sulfate, and cadmium nitrate, respectively.[8][5]
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 + 2 Ni(OH)2
References
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