Copper(II) carbonate

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Copper(II) carbonate
Copper (II) carbonate
Identifiers
CAS number 1184-64-1 YesY
PubChem 14452
ChemSpider 13799 YesY
RTECS number FF950000
Jmol-3D images Image 1
Properties
Molecular formula 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
Solubility in water insoluble
Solubility soluble in acetic acid
Thermochemistry
Std molar
entropy
So298
88 J·mol−1·K−1
Std enthalpy of
formation
ΔfHo298
−595 kJ·mol−1
Hazards
MSDS Oxford MSDS
LD50 159 mg/kg (rat, oral)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
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Infobox references

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 heated, it thermally decomposes to form CO2 and CuO, cupric oxide, a black solid.

Basic copper(II) carbonate patina on roofs of Château Frontenac.

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[edit]

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[edit]

  1. ^ Masterson, W. L., & Hurley, C. N. (2004). Chemistry: Principles and Reactions, 5th Ed. Thomson Learning, Inc. (p 498).

External links[edit]