CHRIS25
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Colour Changes when NaOH added to CUCL2 and water
Questions come from this Basic reaction: Copper + HCL + AIR, and then 1 mil of this solution added to 30mils of water and then 1 mil of NAOH added to
this. NAOH is 1mole. Moles of cucl2 and cucl1 unknown as is the HCL amount (After three weeks).
When Copper chloride (1mil) is in balanced solution with 30mils water I see no colour change, when the copper chloride solution becomes more
concentrated with CL2 ions I see adding this to the same amount of water 30mils a pale blue colour is seen. Obviously the Cu2 ions. Adding more
cucl2 turns it more greenish, these would be the chloride ions.
Now When I add 1ml of Sodium Hydroxide to the unsaturated solution of 30 mils water and 1 mil copper chloride a pale creamy white precipitate is
formed (copper hydroxide) which quickly dissolves. However if 1mil of a saturated solution of copper chloride is in that same amount of water and
then 1mil of sodium hydroxide is added the copper hydroxide is a heavy green colour and immediately one sees a white precipitate of what can only be
sodium chloride settling at the bottom of the flask.
Is this heavy green colour an excess of CL2 or CL1 or still the copper hydroxide, and when the sodium chloride solids are precipitated to the bottom
of the flask is this a sign of excess chloride ions(1 or 2) in the original copper chloride solution.
I am still grappling and fighting to get a real understanding of what is going on with my etchant solution. Hence the basic questions still going on
in this area.
‘Calcination… is such a Separation of Bodies by Fire, as makes ‘em easily reducible into Powder; and for that reason ‘tis call’d by some
Chymical Pulverization.’ (John Friend, Chymical Lectures London, 1712)
Right is right, even if everyone is against it, and wrong is wrong, even if everyone is for it. (William Penn 1644-1718)
The very nature of Random, Chance development precludes the existence of Order - strange that our organic and inorganic world is so well defined by
precision and law. (me)
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woelen
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Could you please be more careful in the use of chemical symbols and notation?
Please use the correct case of letters. Do not write CUCL2 or cucl2, but CuCl2.
Furthermore, you are talking about CL2 ions, Cu2 ions and Cu1 ions. It is all very fuzzy and I have to guess what you mean. Write Cu(2+) and Cu(+), or
even better, if you want to use superscripts, use Cu<sup>2+</sup> and Cu<sup>+</sup>. What do you mean with CL2 and CL1??
If you are precise in formulating then it may even help you understand what you are doing. Good understanding starts with being precise! So,
reformulate what you write, be more precise and then I'm certainly willing to help you explain a few things. I have done a lot of experimenting and
have read a lot about copper chemistry and there is a good chance that I can help you understanding what is going on.
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CHRIS25
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Point taken Woelen, still having to adjust from switching between artistic mode and correct scientific nomenclature. My background is solidified in
Languages and Art so I will keep doing my best in the scientific language.
When I syringe in 1 ml of Copper chloride to a solution of 30mils water (at the beginning stages of etchant solution) I see no colour change, but when
the copper chloride solution becomes more concentrated (as a result of many etchings) with Cl(+2) ions I noticed that syringing this to the same
amount of water (30mils) that a pale blue colour appears. I assume this to be the high concentration of Cu(+2) ions? But...As I add more CuCl2 to
this same 30 mil of water it turns more greenish, these I assume this to be the excess Cl(+2) ions shifting the balance from copper concentrate to
chloride concentrate, In reverse so to speak I have understood that adding water to copper chloride it will be a green-blue, as you add water it
shifts to blue and as you add more chloride ions it shifts to green, (my personal observation).
Now When I add 1ml of Sodium Hydroxide to the Unsaturated solution of 30 mils water (the beginning etchant) and 1 mil copper chloride, a pale creamy
white precipitate is formed (copper hydroxide) which quickly dissolves. However if 1mil of a Saturated solution of copper chloride (after many
etchants) is in that same amount of water (30 ml) and then 1mil of sodium hydroxide is added, the copper hydroxide is a heavy green colour and
immediately one sees a white precipitate of what can only be sodium chloride settling at the bottom of the flask.
Is this heavy green colour an excess of Cl(+2) or Cl(+1) or still the copper hydroxide, and when the sodium chloride solids are precipitated to the
bottom of the flask is this a sign of excess chloride ions(+1 or +2) in the original copper chloride solution.
I apologise if this last sentence seems confusing, I think that reflects what I am really trying to understand. Please feel free to correct any
nomenclature mistakes I may have made - don't see any at the moment. Oh, have yet to learn how to do superscripts on my apple keyboard - so once I
find that out there should be more improvements. Thankyou.
‘Calcination… is such a Separation of Bodies by Fire, as makes ‘em easily reducible into Powder; and for that reason ‘tis call’d by some
Chymical Pulverization.’ (John Friend, Chymical Lectures London, 1712)
Right is right, even if everyone is against it, and wrong is wrong, even if everyone is for it. (William Penn 1644-1718)
The very nature of Random, Chance development precludes the existence of Order - strange that our organic and inorganic world is so well defined by
precision and law. (me)
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woelen
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You are writing about Cl(2+) and Cl(+) ions. These do not exist.
What you have in solution are Cl(-) ions and Cu(2+) ions.
The color changes can be understood quite well.
Copper(II) ions do not exist as "naked" ions, but they are coordinated to water molecules and/or chloride ions.
If no chloride ions are present at all, such as in a solution of copper sulfate, then the Cu(2+) ions are coordinated to water molecules. In fact, in
reality you have no Cu(2+) ions at all, but ions like Cu(H<sub>2</sub>O)<sub>6</sub><sup>2+</sup>. These ions have
a nice sky-blue color.
When the concentration of chloride ions, Cl(-), increases, then water molecules are exchanged with chloride ions. E.g. two water molecules may be
replaced by a single chloride ion, resulting in an ion which can be written as
[CuCl(H<sub>2</sub>O)<sub>4</sub>]<sup>+</sup>. The higher the concentration of chloride ions, the more water
molecules are replaced. This can go all the way up to CuCl<sub>4</sub><sup>2-</sup>. A maximum of 4 chloride ions can be
coordinated to a single copper(II) ion and then all water molecules are replaced. The more water molecules are replaced by chloride ions, the more the
color shifts from blue to yellow/brown. Intermediate colors are cyan, green, olivegreen. At extremely high concentration of chloride ions, such as in
concentrated hydrochloric acid the solution looks yellow or even brown/yellow.
A similar thing also occurs with precipitates of copper(II) salts. If no (or hardly no) chloride is present, then your precipitate contains a mix of
hydroxide ions and water molecules coordinated to the copper ions. Such a precipitate is pale blue. When more chloride is present, then the
precipitate contains a mix of hydroxide ions, chloride ions and water molecules and the color of such a precipitate is greenish and this can go to
fairly dark green. Such a dark green precipitate may have approximately as much chloride ions as hydroxide ions in its solid form. This is called
basic copper chloride and the dry powder is a nice green (this usually looses water on drying and forms a mixed chloride/oxide):
[Edited on 4-6-12 by woelen]
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CHRIS25
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Thankyou woelen, this makes things clearer, and brings together quite nicely all those jagged jigsaw pieces of reading that I have been doing. Now I
think I begin to see a much clearer picture of the whole reaction. And your explanation is very clear, thankyou.
However - just one thing, I have read so often, concerning etchant solutions, the expression: CuCl(+1) and CuCl(+2), or sometimes as CuCl1 and CuCl2.
Why is this then written so if Cl(+1) and Cl(+2) don't exist?
[Edited on 4-6-2012 by CHRIS25]
[Edited on 4-6-2012 by CHRIS25]
‘Calcination… is such a Separation of Bodies by Fire, as makes ‘em easily reducible into Powder; and for that reason ‘tis call’d by some
Chymical Pulverization.’ (John Friend, Chymical Lectures London, 1712)
Right is right, even if everyone is against it, and wrong is wrong, even if everyone is for it. (William Penn 1644-1718)
The very nature of Random, Chance development precludes the existence of Order - strange that our organic and inorganic world is so well defined by
precision and law. (me)
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Vargouille
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I believe it is to state the oxidation state of the copper ion. CuCl has copper lacking one electron, thus the single positive charge, while CuCl2 has
copper lacking two electrons. The (+1) and (+2) designations I believe are a modified version of the written name for the salts: copper (I) chloride
and copper (II) chloride, respectively.
As a comment, Cl+ and Cl+2 *may* exist for an incredibly short amount of time *if* an incredibly powerful oxidizer could be synthesized. It would be
amazing science and probably incredibly dangerous because of how much energy it would take to strip an electron from chlorine, and even more so to do
it twice. That's theoretical chemistry, though, and although very interesting, not incredibly relevant.
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barley81
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In an electrified tube filled with chlorine gas at low pressure, there are probably a few Cl<sup>+</sup> ions floating around. You have a
better chance of making tiny amounts of the transient species Cl<sup>+</sup> in this way than using chemicals.
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woelen
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CuCl(+1) and CuCl(+2) are no valid chemical notations and should not be used.
There are two types of copper chloride. There is copper(I) chloride and this has formula CuCl. There also is copper(II) chloride and this has formula
CuCl<sub>2</sub>. The first one can be considered a combination of Cu(+) ions and Cl(-) ions and the latter can be considered a
combination of Cu(2+) ions and Cl(-) ions (actually, the above is a simplification, but for the time being it should be sufficient for your
understanding).
I think you should buy a book on basic chemistry. Try to understand what elements there are, what their chemical symbols are. Then try to get an idea
of what a molecule is, how molecules can be represented by a formula and a structural drawing and then you can try to understand ionic species like
Cu(2+) and Cl(-). This will take some studying, but it will be really rewarding. The understanding it gives will make the subject much more
interesting.
[Edited on 5-6-12 by woelen]
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