[woelen]

ok great, as soon as im home ill try this. of course like everything else ive thoguht would work, nothing has. heres why I think this. I conducted a flame test on that compound. had it been a copper compound it sohuld have flamed green. It flamed orange/yellow, which is what sodium does. So.. unless yet again my logic is flawed here, this cant be a copper compound.

another thing that caught my attention is this. using a graphite anode in the reaction yeilded Cl₂. This is cuz the Cl₂ has nothing to reacti with so it bubbled up, possibly with O₂, but that is irrelevant. I knew what it was cuz I could smell it. When it is replaced by a copper anode, i do not smell Cl₂. It would be reasonable to say that the copper reacted with the chlorine then, correct? if so, that I HAVE to making a copper chloride-like compound. I guess it could be hypochlorite also, but

If you use copper as anode, then in the first place, you do not get chlorine at all. You do not first get chlorine, which in turn reacts with copper, you immediately get copper ions (either copper (I) or copper (II) or both, depending on precise reaction environment). As I explained to you with the magnesium/aluminium/HCl experiment, a similar effect works here.

When you perform electrolysis with a graphite anode, then the electrons, drawn from the anode by the voltage source (your 9V battery) can be taken from

Cl(-)
H2O
C

(in a leter stage also from OH(-))

The most facile electron donor in this case is Cl(-), so you get 2Cl(-)  --> Cl2 + 2e, with the electrons absorbed by the voltage source (and a same number of electrons emitted at the cathode).

If you have a copper anode, then the set of compounds, capable of delivering electrons looks as follows:

Cu
Cl(-)
H2O

Now the copper metal is the most facile source of electrons. So, the electrons are taken from the copper right away and no chlorine is formed.

Wilco

[Xeluc]

Ok I get it.. I for some reaon have this idea stuck in my head that the oposite charges "rip apart" the ionic compoundin the middle of the solution. I need to pound into my head that it happes ON the anode and Cathode... So thanks for that.

Now.. I boiled my CuCl2 today. Its awesome. My first ionic compound synthesized that i TRIED to do. Its green... awesome.. I played with its hyrdrating abilites for like 10 minutes.. heheh... anyhow that was a succsess (i used HCl, H₂)O₂, and copper wire.) So... cool

Now before this topic closes up, I have one more thing id like you guys to specify. I know that the H₂)O₂ Helps the Hcl disolve the Copper, i guess i coulda inferred that. It's very important that I know the exact process though. Could someone give me a balanced equation of what you start with and what you end up with. I dont know if the H₂)O₂ is a catalyst and isnt used up, or if its needed jsut as the Hcl. A balanced equation would help me make more of this without wasting acid. (I'm trying to fill up a little CuCl₂)-safe jar ).

Another thing I don't get is why single replacement reactois dont work in water. I mean I know of the thermite reactoion. but i guess that wouldnt happen in water.. SO what rol edoes it play?

THANKS SO MUCH GUYS. I really appreciate all the help in this forum, My chem teacher isnt exactly around and hed prolly be scared if i knocked on his door asking quesitons.. lol

EDIT: oh yeah, one last thing. I took some of the liquified CuCl₂ and put it in container filled with water. the solutuion was blue, no green. did i make a new compound or is that was diluted CuCl₂ looks like.. Also, i saw a sample of CuCl₂ and it was that same blue color. My solid is Green, altho I have seen it turn blue when some of the liquid splashed out and evaporated. I am thinking that the green color is because of residual HCl, is this the case?

[woelen]

Ok I get it.. I for some reaon have this idea stuck in my head that the oposite charges "rip apart" the ionic compoundin the middle of the solution. I need to pound into my head that it happes ON the anode and Cathode... So thanks for that.

Now.. I boiled my CuCl2 today. Its awesome. My first ionic compound synthesized that i TRIED to do. Its green... awesome.. I played with its hyrdrating abilites for like 10 minutes.. heheh... anyhow that was a succsess (i used HCl, H₂)O₂, and copper wire.) So... cool

Now before this topic closes up, I have one more thing id like you guys to specify. I know that the H₂)O₂ Helps the Hcl disolve the Copper, i guess i coulda inferred that. It's very important that I know the exact process though. Could someone give me a balanced equation of what you start with and what you end up with. I dont know if the H₂)O₂ is a catalyst and isnt used up, or if its needed jsut as the Hcl. A balanced equation would help me make more of this without wasting acid. (I'm trying to fill up a little CuCl₂)-safe jar ).

The net reaction is the following:
  Cu + H2O2 + 2HCl  -->  CuCl2 + 2H2O

So, the process uses HCl and H2O2.

What occurs in reality, however, is WAY more complex than the simple equation suggests. Copper chemistry is remarkably complex. Just to give you an idea, the chloride ions play an important role in this reaction. E.g. if you do the same with hydrogen peroxide and dilute sulphuric acid, then you'll  see that the reaction is much slower. The special thing is that Cu²⁺ forms a chloro-complex, which is very reactive and which is capable of oxidizing copper metal. The H2O2 in turn is capable of oxidizing the resulting copper (I) chloro-complex.

Just another demo of the reactiveness of the copper-chloro complex.

Take some household aluminium-foil and put this in a concentrated solution of sodium chloride (table salt). You'll see no reaction.
Put some Al-foil in a fairly concnetrated solution of copper sulfate: No reaction.
Put some Al-foil in a fairly concentrated solution of copper sulfate and sodium chloride: The foil quickly dissolves, giving hydrogen and copper metal. Quite a lot of heat is produced.

Put some Al-foil in a solution of copper chloride (now you can do this, because you just made some): The metal dissolves and quite some heat is produced.

Another thing I don't get is why single replacement reactois dont work in water. I mean I know of the thermite reactoion. but i guess that wouldnt happen in water.. SO what rol edoes it play?

The most important reason for this is that in many situations water (and certainly water with acid) is less 'noble' than the metal to be replaced. A replacement reaction can be done in water, when the metal to be released is more 'noble' than water. I.e. when you add a zinc nail to a solution of copper sulfate or silver nitrate, then you'll see the nail being covered by copper or silver.

THANKS SO MUCH GUYS. I really appreciate all the help in this forum, My chem teacher isnt exactly around and hed prolly be scared if i knocked on his door asking quesitons.. lol

EDIT: oh yeah, one last thing. I took some of the liquified CuCl₂ and put it in container filled with water. the solutuion was blue, no green. did i make a new compound or is that was diluted CuCl₂ looks like.. Also, i saw a sample of CuCl₂ and it was that same blue color. My solid is Green, altho I have seen it turn blue when some of the liquid splashed out and evaporated. I am thinking that the green color is because of residual HCl, is this the case?

Many metal ions form complexes in solution.

In water, copper ions form the complex ion Cu(H₂O)₆²⁺. This ion is light blue. You get such a light blue solution if you dissolve copper sulfate or copper nitrate in water.

When chloride is present, then however, chloride ions replace water molecules from the ion. At increasing concentration of chloride, more and more of the water molecules will be replaced by chloride ions. In very concentrated solutions of chloride, the copper ion is completely surrounded by chloride ions: CuCl₄^2-. The chloride ions really are bound to the copper and do not exist as independent ions. A new ion is made, the tetrachlorocuptrate (II) ion. On dilution, the reverse reaction occurs. Chloride ions are replaced by water molecules.

The tetrachlorocuprate ion is yellow/green, the species CuCl₂(H₂O)₂ is green/blue. So, when you dissolve some copper chloride in a small amount of water, you will have green solutions. Try dissolving sone of your CuCl2 in concentrated HCl, which has a lot of chloride in it. You'll see that the liquid becomes yellowish. Then you can see the real color of tetrachlorocuprate.

Your sample of CuCl2 is green instead of cyan-blue, because of the fact that quite some extra water still is in the sample and because of the fact that extra HCl is in the sample. It is hard to remove the last traces of HCl and extra water. Look at http://81.207.88.128/science/chem/compounds/cupric_chloride.html for a nice picture of a sample of pure reagent grade CuCl2.2H2O (do not bookmark this URL, because the IP-address in it is not fixed and may be invalid after some time). The compound is cyan blue. it is not really blue like copper sulfate.

The key to understanding the changes of colors you observe is "coordination complex".

Just another nice thing: Add some excess household ammonia to a small amount of CuCL2. You'll see a deep blue solution, now you get another complex ion Cu(NH₃)₄(H₂O)₂²⁺. Now ammonia molecules replace water molecules from the hexaqua copper ion.

Wilco

[jdurg]

HCl on its own is unable to dissolve copper metal because while HCl is a fairly strong acid, it is a very weak oxidizer.  Therefore, any metal which is below hydrogen on the 'activity series' won't react because the metal refuses to be oxidized by the hydrogen atom alone.  If you look at the relative strengths of acids, you'll see that nitric acid (HNO3) is actually 'weaker' than HCl is, however nitric acid will EASILY dissolve copper metal.  Why is this?  It's because the nitrate ion is a very good oxidizer, and in conjunction with the free hydrogen ions it is able to readily oxidize the copper metal and turn it into copper ions.  (All through a rather complex methods of interactions).  If you've done some chemistry work, you've probably also heard about aqua regia.  Gold metal is not very easy to oxidize, so even nitric acid is unable to oxidize the metal.  The combination of the nitrate and hydrogen ions just isn't enough to oxidize the pure metal into an ion.  However if you mix HCl and HNO3, gold is easily dissolved.  This is because the mixture of the hydrogen ions, the nitrate ions, and free chlorine gas caused by the mixing of the two acids provides the oxidizers needed to dissolve the gold.  (Chlorine gas is a very good oxidizer.  Having a combination of chlorine gas and nitrate ions will oxidize damn near anything).  

When looking at the situation with dissolving copper in HCl and H2O2, think of the HCl as a gun and the H2O2 as a bullet.  On their own, a bullet and a gun won't be able to do much of anything.  But if they are combined and work together, they can produce a heck of a lot of damage.

[Xeluc]

Actually, that is the very picture that made me realize it wasnt green..wouldnt jsut heating it alot or for long periods of time drive of HCl? It obvious drives off water because it dehydrates and turns brown. I figure it if keep disolving it in water and boiling it, your ognna get the HCl to escape, since its a gas...

[woelen]

Actually, that is the very picture that made me realize it wasnt green..wouldnt jsut heating it alot or for long periods of time drive of HCl? It obvious drives off water because it dehydrates and turns brown. I figure it if keep disolving it in water and boiling it, your ognna get the HCl to escape, since its a gas...

It might be that if you heat the solid for a longer time, that you can drive off the HCl, but it will be hard. In fact, HCl forms the tetrachloro complex with copper (II). So, you in reality do not have CuCl2 with some HCl, but you have CuCl2 with some yellow/brown H2CuCl4 incorporated in the solid. The latter is the acid of the tetrachloro complex I mentioned in the previous post.

I would not dissolve all of it in water and try to drive off the HCl, because that will not work. HCl and water form an azeotropic mixture. If the concentration of HCl is less than appr. 20%, then first mainly water will boil away and when the concentration in the remaining liquid has risen to 20%, then a mix, containing 20% HCl boils away. If you start with an acid with more than 20% HCl, then first a mixture, rich in HCl will boil off and when the concentration has dropped to 20%, then a mix, containing 20% HCl boils away.

Many compounds have the property that they form azeotropic mixtures with water (e.g. alcohol, 96% and nitric acid, 68%). Such compounds cannot be removed simply by boiling and the also cannot be concentrated above their azeotropic concentration by means of distillation.

Wilco

[woelen]

HCl on its own is unable to dissolve copper metal because while HCl is a fairly strong acid, it is a very weak oxidizer.  Therefore, any metal which is below hydrogen on the 'activity series' won't react because the metal refuses to be oxidized by the hydrogen atom alone.  If you look at the relative strengths of acids, you'll see that nitric acid (HNO3) is actually 'weaker' than HCl is, however nitric acid will EASILY dissolve copper metal.  Why is this?  It's because the nitrate ion is a very good oxidizer, and in conjunction with the free hydrogen ions it is able to readily oxidize the copper metal and turn it into copper ions.  (All through a rather complex methods of interactions).  If you've done some chemistry work, you've probably also heard about aqua regia.  Gold metal is not very easy to oxidize, so even nitric acid is unable to oxidize the metal.  The combination of the nitrate and hydrogen ions just isn't enough to oxidize the pure metal into an ion.  However if you mix HCl and HNO3, gold is easily dissolved.  This is because the mixture of the hydrogen ions, the nitrate ions, and free chlorine gas caused by the mixing of the two acids provides the oxidizers needed to dissolve the gold.  (Chlorine gas is a very good oxidizer.  Having a combination of chlorine gas and nitrate ions will oxidize damn near anything).  

When looking at the situation with dissolving copper in HCl and H2O2, think of the HCl as a gun and the H2O2 as a bullet.  On their own, a bullet and a gun won't be able to do much of anything.  But if they are combined and work together, they can produce a heck of a lot of damage.

I agree with you, but it does not explain why in particular the combination H2O2/HCl is such a powerful oxidizer. A mixture H2O2/H2SO4 at the same normality is not nearly as potent as H2O2/HCl. The reason for this is the very strong complexing properties of the chloride ion, even in acidic media. The presence of chloride affects the redox potential of many metals in a strong way:

Cu --> Cu(2+) + 2e
Cu + 4Cl(-) --> CuCl4(2-) + 2e

The latter redox reaction can be performed more easily. Another example is the easy oxidation of aluminium foil with a mix of Cu(2+) and Cl(-), as I mentioned in a previous post in response to Xeluc.

An even stronger example of this effect is the cyanide ion. Gold dissolves quickly in a solution of sodium cyanide, simply by picking up oxygen from the air.

The redox couple Au <--> Au(+)  + e  or Au <--> Au(3+) + 3e is very much to the left (the metal), but with cyanide present, the complex [Au(CN)2](-) is formed and for this, even oxygen from air, but also hydrogen peroxide, is capable of oxidizing gold easily. In fact, this phenomenon is used commercially for recovering gold from gold ores, which only contain very small amounts of metallic gold, mixed with a lot of rock/debris.

Wilco

[jdurg]

Perhaps there's also the fact that H2O2 will react directly with the H2SO4 forming a different species all together.  The formation of that different species (I think it's monoperoxysulfuric acid) may prevent the rapid oxidation of copper metal?

[woelen]

Perhaps there's also the fact that H2O2 will react directly with the H2SO4 forming a different species all together.  The formation of that different species (I think it's monoperoxysulfuric acid) may prevent the rapid oxidation of copper metal?

The acid you refer to also is called Caro's acid, H2SO5. This is not formed with dilute sulphuric acid (with dilute I also mean 30% acid, comparable in strength with 30% HCl). In a dilute solution of H2SO4 with H2O2, you simply have H(+), HSO4(-), SO4(2-) and H2O2.

If you mix 1 volume of 30% H2O2 and 4 volumes of 95+ % concentrated sulphuric acid, then you get so called 'piranha solution', but that is a whole different story. That solution does contain H2SO5. Never ever attempt to make that stuff in appreciable quantities, because it is very itchy and goes BOOM, apparently without reason. If a hair from your head is going into the liquid, then it may be set off already.

Wilco

[jdurg]

Yeah, I've heard that when the stuff comes in contact with any type of 'organic molecule' it causes a VERY rapid reaction to occur.

[Xeluc]

Hey guys,

I had some CuCl₂ in a solution and some spilled onto the hot metal and was Copper-Plated. I thought CuCl₂'s decomposition temp was like 1800 F... theres no way it was that hot.

[xiankai]

it may be due to a displacement reaction with a more reactive metal u mentioned, that displaced copper from its solution.

[Xeluc]

guess thats it,,, thanks!