Sciencemadness Discussion Board

Copper carbonates - Basic & Copper II - molar amounts

RogueRose - 19-4-2018 at 17:15

I was comparing some copper carbonates to CuO with regard to price at an online reseller, carbonate was $7.10/lb and CuO is $18.90/lb. It doesn't state the type of carbonate but I thought I would be able to tell by the molar mass, and found something odd in wiki.

Wiki listing
CuCO3 = 123.55g/mol
Cu2(OH)2CO3 (basic copper carbonate) = 123.55

Now this is obviously wrong as per the weights.

Cu = 63.5g/mole
O = 16g/mole
C = 12g/mole
H = 1g/mole

So I have calculated that basic copper carbonate = ~221g/mole while the CuCO3 amount is correct.

When i calculate the difference in molar mass for CuO and basic copper carbonate & the price, it seems that the amounts are equal for equivelant masses of copper in each compound, so that seems to mean my calculation is correct.

So, does anyone know how to submit a change to Wiki or have an account to do so?

j_sum1 - 19-4-2018 at 17:44

CuCO3 does not exist. It is not stable. (This has been discussed before with blogfast stating the definitive word.)

There are two common basic carbonates of copper (II). The most easily produced and the one you are likely to see is malachite, CuCO3Cu(OH)2.H2O. But the hydration can vary a bit. And you can get some azurite included in there as well.
Azurite is Cu3(CO3)2(OH)2.

So, the stiochiometry is not tidy.

RogueRose - 19-4-2018 at 18:44

Quote: Originally posted by j_sum1  
CuCO3 does not exist. It is not stable. (This has been discussed before with blogfast stating the definitive word.)

There are two common basic carbonates of copper (II). The most easily produced and the one you are likely to see is malachite, CuCO3Cu(OH)2.H2O. But the hydration can vary a bit. And you can get some azurite included in there as well.
Azurite is Cu3(CO3)2(OH)2.

So, the stiochiometry is not tidy.


Well then either way, the molar amounts are way off from the 123.5g listed. They have either 2 or 3 copper at 63.5g each, so the minimum would be 127g for Cu2 and 190.5g for Cu3 and then you have to add the hydroxide and carbonate to each of these. That was the point of saying the listing of the molar amounts is not correct.

Tsjerk - 19-4-2018 at 20:06

It's Wikipedia, why don't you change them?

Bert - 19-4-2018 at 21:29

One more time:

Free information on the internet is often worth exactly what you paid for it.

Be the change you want to see.

RogueRose - 19-4-2018 at 22:24

I was trying to find out how to change it, but I didn't see any place to make corrections. I'm still looking.

Fulmen - 20-4-2018 at 00:11

Top right of the page (desktop version): https://en.wikipedia.org/w/index.php?title=Copper(II)_carbonate&action=edit