Cadmium hydroxide

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]

Cadmium hydroxide

Cadmium hydroxide structure
Names
IUPAC name Cadmium(II) hydroxide
Identifiers
CAS Number	21041-95-2 Y
3D model (JSmol)	Interactive image
ChemSpider	8488675 Y
ECHA InfoCard	100.040.137
PubChem CID	10313210
UNII	6Y413R87BT Y
CompTox Dashboard (EPA)	DTXSID9066671
InChI InChI=1S/Cd.2H2O/h;2*1H2/q+2;;/p-2 Y Key: PLLZRTNVEXYBNA-UHFFFAOYSA-L Y InChI=1/Cd.2H2O/h;2*1H2/q+2;;/p-2 Key: PLLZRTNVEXYBNA-NUQVWONBAA
SMILES [Cd+2].[OH-].[OH-]
Properties
Chemical formula	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)
Solubility in water	0.026 g/100 mL
Solubility product (Ksp)	7.2×10−15 [1]
Solubility	soluble in dilute acids
Acidity (pKa)	10[2]
Magnetic susceptibility (χ)	−41.0·10−6 cm3/mol
Structure
Crystal 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). Y verify (what is YN ?) Infobox references

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