Scientific [chemical] reaction of hydrochloric acid and copper

I'd like to explain, to a 6th grade class, what is going on when we rub hydrochloric acid over their copper rubbings. Thank you for your help.

I don't know quite what a "copper rubbing" is or what happens to it. In theory, though, hydrochloric acid does not dissolve copper but it does dissolve copper oxides.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

We have been doing descaling of copper shell and tube condensers with hydrochloric acid. what will be the reaction copper tubes? advise what precautions should be taken

Hi, Raj. The reaction is actually pretty simple: HCl acid dissolves copper II oxide --

CuO + 2 HCl => CuCl₂ + H₂O

But as for "what precautions should be taken", sorry, but there is no way to answer that loaded question in the abstract. Good luck.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

Our condenser tube material is Copper; it is choked by strong Ca and silica. Very hard scale.
We were trying to clean it by Hydrochloric Acid, but only 10% was removed. Can I use Hydrofluoric Acid (HF) to remove this strong silica scale?

Hi, Anwar. HF should be strong enough to dissolve silica scales BUT if you have to ask, you may not have had sufficient training. HF is horrendously dangerous. Don't even touch it if you have not had hands-on training in its application. It is deadly; it attacks bones so painfully that you may wish you were dead; and it can anesthetize early on so you are unaware that you have been exposed. Among other issues, dangerous amounts of CO2 gas may be produced, causing expulsion of the acid at unexpected time or in unexpected direction.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey