Sciencemadness Discussion Board - Copper(II) Hydroxide !

Copper(II) Hydroxide !

Waffles SS - 17-4-2011 at 02:46

Today i decided to make Copper (II) hydoxide but i got amazing result.
First i put some copper wire into plastic baker and then add nitric acid(55%)(i used fuming hood) brow somke start to envolved(No2) and i got blue solution(Copper nitate solution)
after that i add sodium hydroxide solution to baker and i got dark precipitate!! i think i should get blue precipitate not dark!

Cu + 4HNO3 = Cu(NO3)2 +2 NO2 +2 H2O

Cu(NO3)2 +2 NaOH = Cu(OH)2 + 2NaNO3

trb456 - 17-4-2011 at 03:11

Perhaps too much HNO3? I have a textbook copy of this very experiment that warns to NOT use an excess of HNO3. Either that or your solution is hot, because it sounds like you got copper oxide (brown/black precipitate):

Cu(OH)2 + Δ ─› CuO + H2O

Mixell - 17-4-2011 at 03:26

Copper hydroxide decomposes to copper oxide (CuO) at 80C.
So I assume you added the hydroxide solution to the copper solution while it was still hot, or you dissolved the sodium hydroxide in water and added it immediately to the copper solution.
Excess of nitric acid will just react with the sodium hydroxide and dissolve any copper hydroxide that will form, you will end up with a solution of sodium and copper nitrate (and nitric acid if the amounts weren't stoichiometric with excess of HNO3).

bbartlog - 17-4-2011 at 05:35

I think decomposition begins at even lower temperatures, at least in aqueous solution. Keep everything cold.

Waffles SS - 17-4-2011 at 07:12

Yes, i think most of my copper hydroxide decompose to copper oxide(because the temperature increased to 90c !)
The biggest problem is Nitrogen dioxide. it is highly toxic and lot of it produce in this reaction,next time i want to lead it to concentrated sodium hydroxide solution(sodium nitrite and nitrate will produce)
In other hand copper(II) oxide reacts with concentrated alkali to form the cuprate salts:

2 NaOH + CuO + H2O → Na2[Cu(OH)4]

This mean more sodium hydroxide convert copper oxide
I am looking for better method for make copper hydroxide but unfortunately cooper react very well just with nitric acid.

Anyone has better idea?

[Edited on 17-4-2011 by Waffles SS]

trb456 - 17-4-2011 at 11:00

Got any copper sulfate?

CuSO4 + 2NaOH -> Cu(OH)2 + Na2SO4

If you have sulfuric acid, react with copper (requires electrolysis--forgot this the first time):

Cu + H2SO4 -> CuSO4 + H2

Or, use your copper oxide (no electrolysis)!

CuO + H2SO4 -> CuSO4 + H2O

[Edited on 17-4-2011 by trb456]

woelen - 17-4-2011 at 11:38

You also can work with the copper nitrate, even when excess acid is present.

You need to dilute the solutions and keep them cold. The reaction between excess acid and NaOH is very exothermic and the heat produced in that reaction is enough to decompose Cu(OH)2 to CuO and water. So, dilute your solution to 1/10 of its original volume with cold water and do the same with the NaOH. When you do that, then you'll obtain a blue precipitate. Stir the solution to assure that all of the copper ions react. Add so much NaOH, such that a sample of the liquid after stirring is just slightly basic (e.g. just red to phenolphtalein). Allow the precipitate to settle and decant the solution above it. This should be colorless. The colorless solution may be flushed down the drain, it contains very little copper.

Arthur Dent - 17-4-2011 at 11:50

Quote: Originally posted by trb456

If you have sulfuric acid, react with copper (requires electrolysis--forgot this the first time):

Not necessarily. As per our fellow member Nurdrage's video, you can also use a dilute solution of sulfuric acid with a bit of nitric acid as oxidizer and you'll end up with a good yield of Copper Sulphate solution. His recipe is 30 ml of water, 5ml of H2SO4 and 3 ml of HNO3 and an excess of metallic copper.

I've literally made 100 g of Copper Sulphate with plain telephone wire (adjust the ratio according to your requirements). it's a quick reaction too, after an hour or so when the copper no longer fizzes and the solution is intensely blue, heat the solution a bit and when it has reduced by about half, cool it down and watch the beautiful crystals forming!

Robert

Mixell - 17-4-2011 at 12:57

Hydrogen peroxide and any mineral acid will do the trick, although using nitric acid is a lot cheaper.

Waffles SS - 17-4-2011 at 21:40

I think H2O2 as oxidizer is safer that Nitric acid because it wont make Deadly,nasty,... NO2(my friend damaged by NO2)

Cu + H2O2 + H2SO4 = CuSO4 +2H2O

(Cu + H2O2 = CuO + H2O
CuO + H2SO4= CuSO4 + H2O)

and then:
CuSO4 + NaOH = Cu(OH)2 + NaSO4

I want to try this method and i want to test reaction of copper with sodium hypochlorite

[Edited on 18-4-2011 by Waffles SS]

Mixell - 18-4-2011 at 03:07

Just one thing, H2O2 is very prone to decomposition, and most of it decomposes in the process.
I made CuCl2 using hydrochloric acid and hydrogen peroxide, I ended up using a nice amount of my 33% hydrogen peroxide (about 2-4 times more than the stoichiometric amount needed for the reaction).

woelen - 18-4-2011 at 05:06

H2O2 as oxidizer is not fine if you want to make Cu(OH)2, unless you can be sure that no excess H2O2 is present anymore when the NaOH is added to precipitate the copper(II). Even a slight excess of H2O2 leads to formation of a brown precipitate, which is a mix of copper(II)hydroxide and some peroxo complex of copper(II).

Just as a test, try this:

Dissolve some CuSO4.5H2O in water.
Add some solution of NaOH.

Repeat the same experiment, but now add some H2O2 to the solution of CuSO4.5H2O and then add the solution of NaOH. You'll see a brown/black precipitate.

A nice thing is to add some H2O2 to the blue precipitate of Cu(OH)2. You then see that the precipitate turns dark.

MrHomeScientist - 18-4-2011 at 08:44

I've noticed copper(II) hydroxide's instability myself, too. I tried to make some using the CuSO4 + NaOH method, and I got a very thick, turquoise blue precipitate which looked great. I don't have a vacuum filter, so I used gravity filtration and let it dry. This was a mistake because the precipitate was so thick it stayed wet, and it all decomposed into black CuO.

Sounds like next time I should chill everything down and buy a vacuum filtration setup for best results.

Waffles SS - 18-4-2011 at 08:46

I tried another method today but result wasnt great
First i add some copper metal to solution of 95%sulfuric acid and 50%H2O2(1:1) after 2-3 minutes vigorous reacton start and i lost all of my H2O2 and then i add more H2O2.(this method need lot of hydrogen peroxide)
When i ensured that all of my H2O2 is decoposed then i add cold sodium hydroxide solution and got blue precipitate(Cu(OH)2)
Next time I decide to use aquarium pump replacement for hydrogen peroxide. I think aqurium pump can provide enough oxygen for oxidize copper to copper oxide

2Cu + O2 = 2CuO

CuO + H2SO4 = CuSO4 + H2O

copper oxide Rage

Poppy - 10-1-2013 at 10:40

That was caused because your copper hydroxide was still wet so bearing the formula CuO.H2O or perhaps Cu(OH)2.H2O which makes it prone to dehydrating. If you stand the hydroxide decanting for a long period of time it will vanish its water of hydration and will be considered "dry" even dumped into water.
This was particularly frustating for me since I could no longer produce the oxide even at 95° C elsius high.
:mad:

violet sin - 11-1-2013 at 01:50

electro chem? EASY

epsom salt solution + copper electrodes (one electrode at top + one at bottom of solution with a plastic sleeve) + electricity = Cu(OH2) blue gel ppt.

really easy to set up and monitor regularly. not so easy to gravity filter Cu(OH)2, much like Ni(OH)2 texture, but blue. even harder to rinse unless you wanted to decant a bunch of times or have a vac. saw it a few times on you tube, mine was contaminated with Mg(OH)2. came out as a fine whit powder mixed with the black copper oxide after heating.

White Yeti - 11-1-2013 at 13:37

My experience with copper hydroxide is that it's a royal pain to gravity-filter, in fact I strongly recommend against it. I finally resorted to using paper towels to siphon off the entrapped liquids because it was taking so long. It was a big mess and a big waste. Even at room temperature copper hydroxide will dehydrate to copper oxide, so unless you have a good use for it, it's not worth making it in large quantities.

Manifest - 11-1-2013 at 14:02

How would this work out?

I would of thought the copper wouldn't displace the sodium.
I'm probably wrong...

violet sin - 11-1-2013 at 17:04

it doesn't turn to the oxide unless you heat it. I have had like 1/3 of a gallon milk jug full of pretty blue paste for well over 11 months and not a single black speck in it. only when I put it on the stove did it change. I have been decanting and changing the water in an attempt to "wash" it. don't need it right now so not a prob for me. easy peasy.

from what I remember the electrolysis of the MgSO4 solution sends the Mg+2 over and tries to reduce it, but because of its activity it just oxidizes the copper electrode and stays in solution as Mg+2. starts churning out lots of blue flocculant ppt. that eventually settles.

and YES IT IS A FREAKING PAIN to filter. and I also tried to wick the moisture out with a draping towel but the epsom salt dried on the paper and it stopped leaching out. though I did find that if you got it settled and decanted, put the blue paste in a few paper towels inside a regular dish towel, that you could squeeze out the water by twisting it. don't try it with just the paper though cause it will pop through and go all over your stove and on you running burner... oh wait that was just me lol. learning curve. also I imagine you could easily pour it into a water bottle and cut/drill 1 or more holes in the lid, then put paper towel or cloth inside the cap. screw the cap back on, hold it upside down and squeeze... water will go out like it was under pressure cause it is.

there is more than enough to go on floating around youtube. and shoot your power supply could easily be an appropriate DC transformer from what ever. ya know the black box with a cord like thing that plugs into the wall and then into some printers, walk man, stereo, what ever. a thrift store here has a few baskets of em for 50cents each. I did all my experiments with a hacked ATX computer power supply( upgraded my PC) but any way I ran on 12V rail. so any of the lill transformers around 12V and I don't know maybe 1 amp or so if you can source one. 500mv would still work just slower, but SOOOO easy. just don't use one that you want b/c they don't like the load of a Cu(OH)2 cell as much as the device they were made for and some crap out quick.

White Yeti - 12-1-2013 at 09:01

I've done electrolysis before, but I've always been limited by the capacity of my power supply. Sodium carbonate is a good electrolyte as far as I have seen. The important thing to remember is to use an electrolyte whose anion will not get oxidized at the anode, carbonate is very stable all things considered, so is sulphate. Chloride, for example is not, it will oxidize to free chlorine and hypochlorite, and an electrolysis will produce a motley of products.

I'm not the only one who has seen this decomposition:
http://www.youtube.com/watch?v=nDP3ShdbC5k

My goal is to make copper oxide anyway, so this is actually doesn't matter too much.

ElectroWin - 12-1-2013 at 11:09

I seem to recall slowly adding sodium bicarbonate into copper sulfate solution and getting lovely blue copper hydroxide (and lots of bubbles!)

White Yeti - 12-1-2013 at 15:05

No, the precipitate would be copper carbonate. Same colour, different texture, much more stable, and easier to filter than copper hydroxide. Decomposition of copper carbonate takes place at around 150C.

violet sin - 12-1-2013 at 15:28

ya I was going for CuO also. wanted to play with flame color and try some fast thermite

but leaching out all the epsom was a problem.. less than desired speed w/ thermite. still had fun, though I wasn't able to get the sodium carbonate to do much. I also had read that it was a decent alternative to epsom and easier to deal with, but my cell/PSU said NO! prob should have acid etched my older electrodes first. but any way it didn't conduct. I didn't wanna spend 20$ on a pound of Cu Sulfate to make the oxide when I collect copper metal from my jobsites.. piles of copper everywhere. soo electrolysis was easiest route for me. only cost was time and a lill electricity

White Yeti - 13-1-2013 at 11:44

I think it's easier to turn copper sulphate to oxide. I find that making copper oxide by electrolysis is a real hassle, and I would much rather take a pound of copper sulphate, mix with an equivalent amount of sodium carbonate and filter off the carbonate. There is no better or best way, there's just what you're willing to do to make it work. I can't obtain copper sulphate, so I have to make the acetate myself instead. That in and of itself is a hassle.

violet sin - 13-1-2013 at 20:33

ya I hear ya, thats what I like about this forum. people all trying to get to the same point, but many circumstances and starting materials are different for each. it helps round out the knowledge base coming at it from all sides if you ask me. good stuff. hope my input helped a bit.

AJKOER - 25-1-2013 at 08:51

Quote: Originally posted by Mixell

Just one thing, H2O2 is very prone to decomposition, and most of it decomposes in the process.
I made CuCl2 using hydrochloric acid and hydrogen peroxide, I ended up using a nice amount of my 33% hydrogen peroxide (about 2-4 times more than the stoichiometric amount needed for the reaction).

I would not recommend a HCl/H2O2 route as this could result in the formation of some Copper oxychloride. If HCl reacts with even dilute H2O2, some HOCl is formed which could create the unstable Copper hypochlorite. The latter decomposes into Cupric chloride and Copper oxychloride.

Here is my prior post comment on this topic:

Source: http://www.sciencemadness.org/talk/post.php?action=reply&...

Quote: Originally posted by AJKOER

First, a limited hydrolysis of CuCl2 in water:

CuCl2 + 2 H2O <----> Cu(OH)2 + 2 HCl

But, with the addition of Hydrogen peroxide:

H2O2 + 2 HCl (dilute only) --> 2 HOCl

This reaction is cited by Watt's as one of several preparations for Hypochlorous acid. To quote from "Watts' Dictionary of chemistry", page 16. "—6. Addition of H2O2 Aq (containing 2.45 p.c. H2O2) to a large excess of Cl Aq produces HClOAq, according to Fairley (B. A. 1874, 57); if much H202 is added, the HClO Aq is decomposed forming HCl Aq, H20, and evolving O." Link: http://books.google.com/books?pg=PA13&dq=Watt+preparatio...

Next, the reaction of dilute HOCl and Cu(OH)2, forming Copper Oxygen Chloride, a greenish crystalline double salt, CuCl2.Cu(OH)2, which is insoluble in water.

2 Cu(OH)2 + 4 HOCl --> 2 CuCl2.Cu(OH)2 + 2 H2O + O2

You should also see some oxygen bubbles. The reaction is actual more complex with the intermediate formation of Copper hypochlorite, which decomposes forming the oxychloride and, per the reference below, actually leaves some CuCl2 in solution.

Reference: "A comprehensive treatise on inorganic and theoretical chemistry", Volume 2, by Joseph William Mellor, page 271. To quote:

"R. Chenevix notes the ready solubility of cupric oxide in chlorine water, and P. Grouvelle found that the soln. obtained by passing chlorine into water with cupric oxide in suspension possessed bleaching properties, and these were retained even after the soln. had been boiled for a quarter of an hour. A. J. Balard found that the distillation of P. Grouvelle's liquor furnished some hypochlorous acid and a green oxychloride, 3CuO.CuCl2.4H20, was formed in the retort. A. J. Balard prepared a soln. of cupric hypochlorite by dissolving cupric hydroxide in hypochlorous acid. It is also made by the action of cupric sulphate on calcium hypochlorite. A. J. Balard found that copper filings are partially dissolved by hypochlorous acid, the soln. after standing some time contains cupric chloride, and deposits a green pulverulent cupric oxychloride."

Link:
http://books.google.com/books?pg=PA269&lpg=PA274&dq=...

[Edited on 9-4-2012 by AJKOER]

[Edited on 25-1-2013 by AJKOER]