Copper(II) hydroxide

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Copper(II) hydroxide
Image:Copper(II) hydroxide.jpg
Systematic name	Copper(II) hydroxide
Other names	Cupric hydroxide
Molecular formula	Cu(OH)₂
Molar mass	97.561 g/mol
CAS number	[20427-59-2]
Density	3.37 g/cm³
Solubility (water)	Insoluble
Melting point	xx.x °C
Boiling point	xx.x °C
Disclaimer and references

Copper(II) hydroxide (chemical formula Cu(OH)₂) is the hydroxide salt of the metal copper, with atomic mass approximately 97.561 atomic mass units. The typical color of copper hydroxide is blue. Some forms of Copper Hydroxide are sold as "stabilized" copper hydroxide, quite likely a mixture of copper carbonate / hydroxide. These are often greener in color.

It can be produced by adding a small amount of sodium hydroxide (NaOH) to a dilute solution of copper(II) sulphate (CuSO₄ · 5H₂O). Treat the experiment with great care; sodium hydroxide (lye) is very corrosive and should be handled using rubber gloves and protective gogles.

"Copper in moist air slowly acquires a dull green coating. The green material is a 1:1 mole mixture of Cu(OH)₂ and CuCO₃:^[1]"

2Cu(s) + H₂O(g) + CO₂ ---> Cu(OH)₂ + CuCO₃(s)

Alternatively, copper hydroxide is readily made by electrolysis of water with a copper anode (+). Scrap copper water piping is a good source of copper for this method. Use a low voltage DC supply (4.5 to 12V) capable of supplying 1A, hammer flat two short lengths of copper piping and connect them to the power supply, place the electrodes on opposite sides of a jar ensuring that they cannot touch and fill the jar with tap water. Switch on the power supply, bubbles should immediately start rising from the cathode (-), if not add a pinch of table salt to the water and stir. The salt allows the water to conduct electricity better. Turquoise copper hydroxide flakes should soon be visible in the water. The gas released by this electrolysis cell is hydrogen; it will readily disperse but if allowed to accumulate can form an explosive mixture.

Copper hydroxide has been used, as an alternative to Bordeaux mixture as a fungicide and nematacide - see [1]. Nowadays, copper hydroxide is disfavored because of environmental contamination problems.

[edit] Precautions

Copper(II) hydroxide is a skin, eye and respiratory irritant. Always wear safety glasses when handling copper hydroxide. In case of contact with eyes, rinse immediately with plenty of water and seek medical advice.