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Techniques for CollectorsMalachite and HCL Reactoin

31st Jan 2006 15:17 UTCRayOfOz

I am doing an example in class in which we powder malachite and add to it 5% HCL, then add an iron object to extract the copper (field test for malachite). I was wondering if anyone could complete/correct this formula reaction for me. I'm not all that great at chemical equations.

Cu2(CO3)2(OH)2 + HCL → CO2 + H2O + Cu2CL ???

Any help would be greatly appreciated.

1st Feb 2006 09:15 UTCPeter Haas

Your malachite formula is wrong. The overall reaction is:

Cu2(CO3)(OH)2 + 4 HCl -> CO2 + 3 H2O + 2 CuCl2

2nd Feb 2006 14:29 UTCRayofoz

Thanks!

The formula for Malachite I took directly from Simon and Schuster's Guide to Rocks and Minerals. I was able to find a complete formula showing the reaction of iron with the cloride ions.

2Fe +Cu2CO3(OH)2 +4 HCL -→ CO2(g) + 3H2O(aq) + 2FeCl2(aq) + 2Cu(s)

8th Mar 2006 13:59 UTCAl Konyers

hi I'm not very good at chemistry and could need some help.

what is the structural formula of malachite?

Are the atoms all connected like in HCl or are they ionic, like NaCl?

8th Mar 2006 14:20 UTCDavid Von Bargen Manager

The carbonate and hydroxl anions will tend to stay together when malachite is dissolved (and are in that state in the solutions from which malachite grows).

http://pubs.acs.org/subscribe/journals/jpcbfk/suppinfo/jp052864i/jp052864isi20050720_015220.pdf?sessid=6006l3

8th Mar 2006 14:36 UTCAl Konyers

Thanks, so if I got you right, the structural formula of malachite would look like this?

http://i2.tinypic.com/qzes1y.jpg

http://i2.tinypic.com/qzes1y.jpg

8th Mar 2006 14:55 UTCDavid Von Bargen Manager

No, actually the structural formula is Cu₂(CO₃)(OH)₂.

A simplified formula would be Cu2CH2O5. The partitioning of the oxygen in the carbonate and hydroxl groups connotates the structural grouping of the anion elements. (the carbonate is actually the carbon surrounded by three oxygens, and doesn't have O-O bonding).

The exact positions of the atoms in the unit cell can be found by searching for malachite at:

http://rruff.geo.arizona.edu/AMS/amcsd.php

22nd Aug 2006 08:13 UTCManas Das

We came to know that considerable amount of dolomite in malachite consume more acid. Therefore, material is rejected for procesing. How do measure dolomitic Index that indicate the dolomite quantity ?

Pls. Help. I need your support

24th Aug 2006 03:40 UTCPaul L. Boyer

My copy of Simon & Schuster's has the formula, Cu2(CO3)(OH)2, given by the esteemed Dr. Haas. Since azurite, Cu3(CO3)2(OH)2 is listed right beside malachite, I wonder if your mind combined the two formulae. Heaven knows my mind has messed with me that way.

6th Mar 2013 12:07 UTCkurt li

But what are the observable reactions?

21st Mar 2013 01:05 UTCAlfredo Petrov Manager

First fizzing, as carbon dioxide is released as bubbles. Then the acid changes from colourless to green-blue as Cu ions go into solution.

21st Mar 2013 05:20 UTCDoug Daniels

Then, if you add a piece of iron, it changes from gray to copper colored, and (ideally) the solution color changes from blue to....greenish (depends on acidity, whether the Fe+2 oxidizes, whether you paid your taxes on time,.....)

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