Basic copper carbonate
| |
| Names | |
|---|---|
| Other names
copper carbonate, cupric carbonate, basic copper carbonate
| |
| Identifiers | |
3D model (JSmol)
|
|
| ChemSpider | |
| ECHA InfoCard | 100.031.909 |
PubChem CID
|
|
| RTECS number |
|
CompTox Dashboard (EPA)
|
|
| |
| |
| Properties | |
| CuCO3 | |
| Molar mass | 123.555 g/mol |
| Appearance | green powder |
| Density | 3.9 g/cm3 |
| Melting point | 200 °C |
| Boiling point | decomposes at 290 °C |
| insoluble | |
| Solubility | soluble in ethanoic acid |
| Thermochemistry | |
Std molar
entropy (S⦵298) |
88 J·mol−1·K−1 |
Std enthalpy of
formation (ΔfH⦵298) |
−595 kJ·mol−1 |
| Hazards | |
| Lethal dose or concentration (LD, LC): | |
LD50 (median dose)
|
159 mg/kg (rat, oral) |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
| |
Copper(II) carbonate (often called copper carbonate or cupric carbonate) is a blue-green compound (chemical formula CuCO3) forming part of the verdigris patina that is found on weathered brass, bronze, and copper. The colour can vary from bright blue to green, because there may be a mixture of both copper carbonate and basic copper carbonate in various stages of hydration. It was formerly much used as a pigment, and is still in use for artist's colours. It has also been used in some types of make-up, like lipstick, although it can also be toxic to humans. It also has been used for many years as an effective algaecide in farm ponds and in aquaculture operations. Copper carbonate was the first compound to be broken down into several, separate elements (copper, carbon, and oxygen). It was broken down in 1794 by the French chemist Joseph Louis Proust (1754–1826). When burnt, it thermally decomposes to form CO2 and CuO, a black solid. It can be used to copper plate a metallic surface by adding sulfuric acid and heat it (to produce copper sulfate) then passing a charge through it with the metal in the liquid. This process is known as electroplating.
Copper in moist air slowly acquires a dull green coating because its top layer has oxidised with the air. Some architects use this material on rooftops for this interesting colour. The green material is a 1:1 mole mixture of Cu(OH)2 and CuCO3:[1]
- 2 Cu (s) + H2O (g) + CO2 + O2 → Cu(OH)2 + CuCO3 (s)
Copper carbonate decomposes at 290 °C, giving off carbon dioxide and leaving copper(II) oxide:
- CuCO3 (s) → CuO (s) + CO2 (g)
Basic copper(II) carbonate occurs naturally as malachite (Cu2(OH)2CO3) and azurite (Cu3(OH)2(CO3)2).
Preparation
Copper carbonate is prepared by combining aqueous solutions of copper sulfate and sodium carbonate. Copper basic carbonate precipitates from the solution:
- 2 CuSO4 + 2 Na2CO3 + H2O → Cu2(OH)2CO3 + 2 Na2SO4 + CO2
The formation of copper carbonate can be verified in the following steps: a) Centrifuge the above mentioned solution, 1 minute at 6000 g is sufficient b) Wash the precipitate with distilled water and centrifuge again c) The colour of the precipitate is blue, like that of several copper salts but none of the sodium salts d) If dilute (1M) hydrochloric acid is added, then bubbles of CO2 will emerge and the precipitate will be fully solubilised. These would not be formed if dilute hydrochloric acid was added to solid Na2SO4.
Pure copper carbonate is obtained from basic copper carbonate in the presence of carbon dioxide at 180 °C and 4.6 MPa (46 atm) pressure. [citation needed]
References
- ^ Masterson, W. L., & Hurley, C. N. (2004). Chemistry: Principals and Reactions, 5th Ed. Thomson Learning, Inc. (p 498).
External links
