HCl alone will not dissolve copper.
HCl + Cu --> no reaction
(copper cannot be oxidized, (or lose electrons) by the acid, to dissolve into solution, as copper is less a reactive than hydrogen in the reactivity series.
The copper needs to be oxidized first; we need H2O2, or a strong oxidizer to begin with, to oxidize some copper into solution, to convert the copper to an oxide in the acidic solution.
Then the copper oxide can be dissolved in the HCl acid forming copper chlorides.
Cu + H2O2 --> CuO + H2O
(For this to react to any extent the solution would need to be acidic)
Cu + H2O2 + 2HCl --> CuCl2 + 2H2O
And
CuO + HCl --> CuCl + H
But with more HCl
CuO + 2HCl --> CuCl2 + H2O
Now we do not need HCl in this acidic solution to dissolve more copper into solution.
Copper II chloride dissolves more copper into solution:
Cu +CuCl2 --> 2CuCl
(So we see our solution of CuCl can hold more copper here than it did as CuCl2)
This solution will contain both CuCl2 and CuCl as a very dark green, almost green brown solution before being saturated with CuCl and precipitating CuCl as a white powder, (temperature, acidity pH, concentration, can also play a big factor in how much copper is held in solution)
Once solution is saturated with copper I chloride it will form a white copper I chloride precipitant, we can add a little HCl and oxygen to rejuvenate the solution:
2CuCl + 2HCl + O --> 2CuCl2
Ready to dissolve more copper into solution
I do not think we can just calculate how much copper that can dissolve into solution with just using the formula 2HCl + Cu --> CuCl2 (actually this equation does not exist), or calculate how much copper is dissolved into solution just using the formula CuCl2 alone, as the solution could be a mix of CuCl and CuCl2, this solution can hold different amounts of copper depending on many factors pH, temperature, concentration and so on, we also see the HCl is not what dissolves copper into solution but actually the CuCl2 which dissolves more copper into solution, the other actions of water acid and oxidizers also come into play.
So with my very limited skills in figuring these chemical equations mathematically I feel it would be very hard to tell exactly how much HCl would dissolve or hold how much copper it would hold in this solution, and I would not even wish to try to figure it out, at least mathematically through chemical equations.
I have used my used copper chloride solution heated it strongly with copper metal and was very surprised at the pounds of copper this solution would dissolve and hold as it became syrupy (on cooling which would convert to copper I chloride salts) (or the amounts of other metals like iron it would dissolve).
I have used this to lower my waste solution volume, as a way of dealing with volumes of waste (if using copper powders previously cemented I can just dry these copper powders).
Or I can dissolve more copper for recovery process using the used solutions (but have to put the copper I powders back into solution if I allow them to form recovering values with this process, so I do not think it saves much acids or reagents, and then the waste solution is brought right back up in volume, so it has very limited gain or uses as a recovery method, (but can be used at times with manipulation of solution before letting solution cool or forming salts).
This can also be used to dissolve steel or iron based metals, by using the copper chloride waste to dissolve iron or steel from scrap forming iron chlorides (which actually helps to dissolve more copper, one thing with strong heating is you will also form insoluble iron hydroxides in mix as red rouge, dealing with these solutions, and recovery of values from the them would be hard to explain, but if you have a fairly good understanding of dealing with the troubles then it is not that hard figure out.
I would not try to calculate this out, but I love it when you guys try, it helps me learn more how it is done.
