The balanced equation for making copper acetate in solution (not anhydrous form):
2Cu + 2CH3(CO2H) +H2O2 = 2Cu(CH3CO2) + 2H2O
I checked this out on a equation balancer site and it was confirmed.
But the problem is that the g/Mole weights do not equalize.
I get the following (allowing for a 5 g/mol discrepency in each molecular weight):
126 + 120 + 32 = 334 + 36
Guess I am not knowledgeable enough to begin to see where the flaw is obviously in something I have done wrong...Tch....
(I forgot to add that I am aware that there are other ways to make copper acetate but since I now have 40% acetic acid this is the easiest method for
me, in the past I mixed 30ml of 5% acetic acid and 15ml of 6% H2O2 and threw in some clean copper, but I want a precise solution and this last method
does not add up 'stoichemetry wise')
[Edited on 13-7-2012 by CHRIS25]cAMP - 12-7-2012 at 17:51
I believe that it's a two-step reaction.
In the first step,
Cu + H2O2 ----> CuO + H2O
Next, the CuO immediately reacts with the acid forming the acetate.
CuO + 2CH3COOH -----> Cu(CH3COO)2 + H2O
Then the equation balances.woelen - 12-7-2012 at 22:39
Your equation is not correct, because you have copper(I) acetate in your result. The correct one is
Cu + 2CH3COOH + H2O2 ---> Cu(CH3COO)2 + 2H2O
Molar weights:
63.5 + 120.1 + 34.0 --> 181.6 + 36.0 (left and right are matching)CHRIS25 - 13-7-2012 at 00:06
cAMP, thanks I should have remembered that copper oxide. That break down was helpful actually for other things that I am just beginning to grasp.
Woelen, as usual I bewray my ignorance. Thankyou, I did not realise that you could get copper1 and 2 acetates. Will look this up to understand more
about their respective differences. Will have to be more careful with the other acetates that I will be making.
Thankyou both, much appreciated.woelen - 13-7-2012 at 01:14
Making copper(I) acetate most likely is very difficult. I searched about this chemical on internet and found only one significant property and that is
its melting point which is said to be 250 C. Not even the color of the solid is mentioned, so it must be a very rare thing.
In practice you only have to consider copper(II) acetate, which is a dark green compound, with a little bit bluish hue.
bbartlog - 13-7-2012 at 11:29
Quote:
Not even the color of the solid is mentioned
Soft, loose, white flakes, according to Gmelin (volume 6 of the Hand-book of Chemistry). It isn't stable in moist air or water (if any oxygen is
present). I've never seen any method of preparation other than dry distillation of cupric acetate. Peach saw some of what I am prety sure was cuprous
acetate when he performed such a distillation: http://www.sciencemadness.org/talk/viewthread.php?tid=10948#...CHRIS25 - 14-7-2012 at 03:35
Woelen, Thanks.
Not sure about the outcome of my presently ongoing reaction, (in the past with the simple 5% vinegar and 6% peroxide and a random piece of copper,
there was a clean piece bubbling away to a blue solution of copper acetate by the morning) and a shiny piece of copper; Now I have parts of the
copper discoloured with black, the oxide obviously, a nice thick blue solution and left wondering what the hell was the point of so much copper and
truly a smelly acidic solution that surely is completely un-useable? Is it my calculations or another case of where mathematics and stoichemetry
destroy intuitiveness? Just took a magnifying glass, the reaction is still ongoing, too small to see even with the naked eye, my eye I mean! I
think, even though I scrubbed the copper with Bicarbonate, placed it into my 3m solution of Sulphuric acid to destroy hidden oxidation layers and then
scrubbed again and then placed into 100% concentrated citric acid, Prisoners escaped!! and that is the black areas on my copper now.
I have a reaction taking place according to the above stoichemetry just discussed. But have had to adjust due to my having only 40% Ethanoic acid
and 6% H2O2.
-- I first calculated the ratios to be 1.86:3.53:1
-- then for my chemicals I had to work out ratios as: 1.86:5.6:1.94
--then (ignoring the density of the acid 1.049g/cm3 as being to small a difference for my purposes)
I calculated by using: 18.6g copper:56ml acid:19.4ml peroxide
Can you suggest something wrong as per my usual story, please?
I forgot to say that I added an extra 20ml peroxide to the solution this morning and the black parts turned to blue then black again, this is not
important anymore, what is important is that the bubbling from the reaction ceased rather quickly. IAfter thinking about all this I am assuming that
I would need to keep on adding peroxide until my hearts content and see what happens, but this means I will be wasting costly peroxide and destroying
my faith in using maths to get consistent results...
Finally why so much copper needed this seems to be a complete nonsense? Yeh, I'm a bit frustrated, and honestly I really don't want to rely on you
tube and unscientific estimates to perform a successful reaction, that is why, ironically, I am now having more problems - probably my maths, don't
know. Thanks.
[Edited on 14-7-2012 by CHRIS25]
[Edited on 14-7-2012 by CHRIS25]
[Edited on 14-7-2012 by CHRIS25]cAMP - 14-7-2012 at 16:44
If I am understanding you correctly, it may be that you need to simply add more acetic acid. The peroxide is doing its job, oxidizing the copper
metal to CuO, but the acetic acid may not be reacting with it fast enough.
You want the acetic acid in excess. You can filter away the acid after collecting the precipitate, and then evaporate off the acid from what's left,
and wash it several times with very cold distilled water to collect the rest of the CuAc2. Or is that not what you're trying to do?CHRIS25 - 15-7-2012 at 00:00
Hallo cAMP, No there is something wrong here. Firstly last night about 30% surface area of the copper pieces were covered with a turquoise layer, I
added another 40mls of H2O2 and the reaction kick started again. This morning there was very very small signs of activity plus those same copper
pieces are very dark green.
Actually to be honest I don't know what I'm looking for anymore. When is the reaction finished? I think I will go back to the U-Tube 60ml 5% vinegar
and 30ml 5% H202. Even they are inconsistent, most sites and home chemistry 'tutorials' I have read say use equal amounts of both reagents. Well who
is right, the maths of stoichemetry or the U-Tubers?
Anyway, a 2:1 ratio seems best and I will use vinegar as per the last three successful productions. Not wasting anymore of precious 40% that I have.
Would have been nice to produce the crytalised form though - probably better fro my purposes.
