Sciencemadness Discussion Board - CuCl2.2H2O synthesis help

CuCl2.2H2O synthesis help

Chemguy5 - 8-8-2018 at 08:54

I need to make some CuCl2.2H2O and I was wondering if all I had to is add copper metal to HCL and add in some H2O2 then evaporate off the water to leave CuCl2. But wouldn't this leave me with anhydrous CuCl2? How do I make the dihydrate?

DraconicAcid - 8-8-2018 at 08:57

If you just let the water evaporate, you will get the dihydrate. You have to heat the dihydrate to get the anhydrous material.

Chemguy5 - 8-8-2018 at 10:09

Duuhhh! I should have known that ! Sorry silly question didn't really think it through

DraconicAcid - 8-8-2018 at 10:29

The only silly question is the one that isn't asked until it's too late.

Or at least, that's what my skydiving instructor used to say.

MrHomeScientist - 8-8-2018 at 11:00

You could also start with malachite and dissolve that in HCl. Evaporating the water yields the green/blue dehydrate and further strong(ish) heating gives the brown anhydrous compound. Copper chloride is neat because it is blue when dilute, but if you increase the chloride concentration (by evaporation or adding another chloride like NaCl) it turns green. Copper chemistry is beautiful.

Swinfi2 - 8-8-2018 at 12:04

Quote: Originally posted by MrHomeScientist

Copper chloride is neat because it is blue when dilute, but if you increase the chloride concentration (by evaporation or adding another chloride like NaCl) it turns green. Copper chemistry is beautiful.

I've been wondering for a two weeks now why my CuCl2 was the wrong colour *facepalm*.

I just used some fine copper wire and ~20%HCl took about a month though. I don't want to be on the governments peroxide list here in the UK.

DraconicAcid - 8-8-2018 at 12:04

Quote: Originally posted by MrHomeScientist

You could also start with malachite and dissolve that in HCl. Evaporating the water yields the green/blue dehydrate and further strong(ish) heating gives the brown anhydrous compound.

And if you don't have malachite, any soluble copper compound can be treated with sodium carbonate or sodium hydrogen carbonate to give basic copper carbonate. This will also react with hydrochloric acid to give the desired compound.

Foeskes - 8-8-2018 at 14:52

I wonder if there was a way to make the solid copper chloride blue.

DraconicAcid - 8-8-2018 at 15:12

Quote: Originally posted by Foeskes

I wonder if there was a way to make the solid copper chloride blue.

Only if you got rid of the chloride and replaced it with something else....so, no.

Foeskes - 9-8-2018 at 02:26

Quote: Originally posted by DraconicAcid

Quote: Originally posted by Foeskes

I wonder if there was a way to make the solid copper chloride blue.

Only if you got rid of the chloride and replaced it with something else....so, no.

Wikipedia seems to suggest that the dihydrate has a blue-green color.
Isn't it green due to the [CuCl4]-2 complex from excess chloride?

woelen - 9-8-2018 at 03:25

Pure copper(II) chloride dihydrate is bright cyan, the anhydrous salt is brown. The cyan color is quite different from the blue of hydrated copper sulfate or copper nitrate.

Foeskes - 9-8-2018 at 06:53

Quote: Originally posted by woelen

Pure copper(II) chloride dihydrate is bright cyan, the anhydrous salt is brown. The cyan color is quite different from the blue of hydrated copper sulfate or copper nitrate.

So how did you make it?
Even my local store sells green CuCl2.

DraconicAcid - 9-8-2018 at 07:33

Quote: Originally posted by Foeskes

Quote: Originally posted by DraconicAcid

Quote: Originally posted by Foeskes

I wonder if there was a way to make the solid copper chloride blue.

Only if you got rid of the chloride and replaced it with something else....so, no.

Wikipedia seems to suggest that the dihydrate has a blue-green color.
Isn't it green due to the [CuCl4]-2 complex from excess chloride?

No, it's far more likely to be tetrahedral [CuCl2(H2O)2]. The tetrachloro complex is yellow.

walruslover69 - 9-8-2018 at 08:27

Assuming your original source of chlorine is HCl, you could probably get rid of it by boiling it down, adding more water and boiling it down again as many times as needed to drive it off.

walruslover69 - 9-8-2018 at 16:42

alternatively, you could probably just rehydrate anhydrous cucl2 to have prepare a sample without CuCl4- contaminants

symboom - 9-8-2018 at 18:04

How about from copper oxychloride
Bleach and copper sulfate forms copper oxychloride add a little hydrochloric acid converting the oxychloride to copper chloride

AJKOER - 14-8-2018 at 07:02

Quote: Originally posted by Chemguy5

I need to make some CuCl2.2H2O and I was wondering if all I had to is add copper metal to HCL and add in some H2O2 then evaporate off the water to leave CuCl2. But wouldn't this leave me with anhydrous CuCl2? How do I make the dihydrate?

The process suggested may also produce a basic copper chloride. Some expected reaction, starting with the presence of copper metal and any created cupric:

Cu(ll)L + Cu = 2 Cu(l)L

The L (for ligand) relating to the formation of a soluble Cu(l) chloride.

Next two possible sources of H+, namely excess HCl, or from an equilibrium reaction between water and the aqua cupric complex:

[Cu(H2O)6]2+ (aq) + H2O (l) = [Cu(H2O)5(OH)]+ (aq) + H3O+ (aq)

Lastly, an electrochemical reaction, consuming the H+ created in the presence of oxygen (from heating in air) or added H2O2:

O2 (or H2O2) + 4 Cu(l) + 2 H+ → 4 Cu(ll) + 2 OH-

which leads to the basic salt.

Possible solution, periodic addition of fine copper powder well dispersed over hot HCl/H2O2. The goal being to limit the creation of cuprous by reducing available copper.

An alternate path, use excess copper and limit chloride presence to reduce the creation of a soluble Cu(l) chloride complex.

Nevertheless, I suspect, it is probably hard to avoid forming some basic salt.

Here is an interesting commentary (possibly dated) found on Atomistry discussing cuprous chloride at http://copper.atomistry.com/cuprous_chloride.html .

[Edited on 15-8-2018 by AJKOER]