Chemistry:Copper(II) carbonate

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Short description: Chemical compound
Copper(II) carbonate
Copper(II)-carbonate-xtal-3x3x3-3D-sf.png
Names
IUPAC name
Copper(II) carbonate
Other names
Cupric carbonate, neutral copper carbonate
Identifiers
3D model (JSmol)
ChemSpider
EC Number
  • 214-671-4
UNII
Properties
CuCO3
Molar mass 123.5549
Appearance gray powder[1]
reacts with water at normal conditions
Structure
Pa-C2s (7) [1]
a = 6.092 Å, b = 4.493 Å, c = 7.030 Å
α = 90°, β = 101,34°°, γ = 90°
5 [1]
Hazards
Flash point Non-flammable
Related compounds
Other anions
Copper(II) sulfate
Other cations
Nickel(II) carbonate
Zinc carbonate
Except where otherwise noted, 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 or cupric carbonate is a chemical compound with formula CuCO3. At ambient temperatures, it is an ionic solid (a salt) consisting of copper(II) cations Cu2+ and carbonate anions CO2−3.

This compound is rarely encountered because it is difficult to prepare[2] and readily reacts with water moisture from the air. The terms "copper carbonate", "copper(II) carbonate", and "cupric carbonate" almost always refer (even in chemistry texts) to a basic copper carbonate (or copper(II) carbonate hydroxide), such as Cu2(OH)2CO3 (which occurs naturally as the mineral malachite) or Cu3(OH)2(CO3)2 (azurite). For this reason, the qualifier neutral may be used instead of "basic" to refer specifically to CuCO3.

Preparation

Reactions that may be expected to yield CuCO3, such as mixing solutions of copper(II) sulfate CuSO4 and sodium carbonate Na2CO3 in ambient conditions, yield instead a basic carbonate and CO2, due to the great affinity of the Cu2+ ion for the hydroxide anion HO.[3]

Thermal decomposition of the basic carbonate at atmospheric pressure yields copper(II) oxide CuO rather than the carbonate.

In 1960, C. W. F. T. Pistorius claimed synthesis by heating basic copper carbonate at 180 °C in an atmosphere of carbon dioxide CO2 (450 atm) and water (50 atm) for 36 hours. The bulk of the products was well-crystallized malachite Cu2CO3(OH)2, but a small yield of a rhombohedral substance was also obtained, claimed to be CuCO3.[4] However, this synthesis was apparently not reproduced.[2]

Reliable synthesis of true copper(II) carbonate was reported for the first time in 1973 by Hartmut Ehrhardt and others. The compound was obtained as a gray powder, by heating basic copper carbonate in an atmosphere of carbon dioxide (produced by the decomposition of silver oxalate Ag2C2O4) at 500 °C and 2 GPa (20,000 atm). The compound was determined to have a monoclinic structure.[5]

Chemical and physical properties

The stability of dry CuCO3 depends critically on the partial pressure of carbon dioxide (pCO2). It is stable for months in dry air, but decomposes slowly into CuO and CO2 if pCO2 is less than 0.11 atm.[6]

In the presence of water or moist air at 25 °C, CuCO3 is stable only for pCO2 above 4.57 atmospheres and pH between about 4 and 8.[7] Below that partial pressure, it reacts with water to form a basic carbonate (azurite, Cu3(CO3)2(OH)2).[6]

3 CuCO3 + H2OCu3(CO3)2(OH)2 + CO2

In highly basic solutions, the complex anion Cu(CO3)22− is formed instead.[6]

The solubility product of the true copper(II) carbonate was measured by Reiterer and others as pKso = 11.45 ± 0.10 at 25 °C.[2][6][8]

Structure

In the crystal structure of CuCO3, copper adopts a distorted square pyramidal coordination environment with coordination number 5. Each carbonate ion bonds to 5 copper centres.[1]

References

  1. 1.0 1.1 1.2 1.3 H. Seidel, H. Ehrhardt, K. Viswanathan, W. Johannes (1974): "Darstellung, Struktur und Eigenschaften von Kupfer(II)-Carbonat". Z. anorg. allg. Chem., volume 410, pages 138-148. doi:10.1002/zaac.19744100207
  2. 2.0 2.1 2.2 Rolf Grauer (1999) "Solubility Products of M(II) Carbonates". Technical Report NTB-99-03, NAGRA - National Cooperative for the Disposal of Radioactive Waste; pages 8, 14, and 17. Translated by U. Berner.
  3. Ahmad, Zaki (2006). Principles of Corrosion Engineering and Corrosion Control. Oxford: Butterworth-Heinemann. pp. 120–270. ISBN 9780750659246. 
  4. C. W. F. T. Pistorius (1960): "Synthesis at High Pressure and Lattice Constants of Normal Cupric Carbonate". Experientia, volume XVI, page 447-448. doi:10.1007/BF02171142
  5. Hartmut Erhardt, Wilhelm Johannes, and Hinrich Seidel (1973): "Hochdrucksynthese von Kupfer(II)-Carbonat", Z. Naturforsch., volume 28b, issue 9-10, page 682. doi:10.1515/znb-1973-9-1021
  6. 6.0 6.1 6.2 6.3 F. Reiterer, W. Johannes, H. Gamsjäger (1981): "Semimicro Determination of Solubility Constants: Copper(II) Carbonate and Iron(II) Carbonate". Mikrochim. Acta, volume 1981, page 63. doi:10.1007/BF01198705
  7. H. Gamsjäger and W. Preis (1999): "Copper Content in Synthetic Copper Carbonate." Letter to J. Chem. Educ., volume 76, issue 10, page 1339. doi:10.1021/ed076p1339.1
  8. F. Reiterer (1980): "Löslichkeitskonstanten und Freie Bildungsenthalpien neutraler Übergangsmetallcarbonate". Thesis, Montanuniversität Leoben.


Carbonates
H2CO3 He
Li2CO3,
LiHCO3
BeCO3 B C (NH4)2CO3,
NH4HCO3
O F Ne
Na2CO3,
NaHCO3,
Na3H(CO3)2
MgCO3,
Mg(HCO3)2
Al2(CO3)3 Si P S Cl Ar
K2CO3,
KHCO3
CaCO3,
Ca(HCO3)2
Sc Ti V Cr MnCO3 FeCO3 CoCO3 NiCO3 CuCO3 ZnCO3 Ga Ge As Se Br Kr
Rb2CO3 SrCO3 Y Zr Nb Mo Tc Ru Rh Pd Ag2CO3 CdCO3 In Sn Sb Te I Xe
Cs2CO3,
CsHCO3
BaCO3   Hf Ta W Re Os Ir Pt Au Hg Tl2CO3 PbCO3 (BiO)2CO3 Po At Rn
Fr Ra   Rf Db Sg Bh Hs Mt Ds Rg Cn Nh Fl Mc Lv Ts Og
La2(CO3)3 Ce2(CO3)3 Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu
Ac Th Pa UO2CO3 Np Pu Am Cm Bk Cf Es Fm Md No Lr