# Stoichiometric reaction of hydrochloric acid, potassium nitrate, and copper

I have the following reaction involving these elements:

• $\ce{HCl}$ (hydrochloric acid)
• $\ce{KNO3}$ (potassium nitrate, a nitrate salt)
• $\ce{Cu}$ (copper)

The reaction should produce nitrogen dioxide ($\ce{NO2}$).

The chemical equation should look like this:

$$\ce{HCl + KNO3 + Cu -> NO2}$$

But I'm clearly missing something. Can anybody help me equalize and complete this equation?

• What kind of reaction is this? Are you putting acid into solution? I assume you don't know the other products and that is what you are looking for?
– Mike
Feb 18, 2017 at 21:51
• I don't really know what is the reaction type. No I'm not putting acid into solution, I'm producing nitric acid using a nitrate salt, copper and hydrochloric acid, I don't know the products yeah that's it Feb 18, 2017 at 21:57
• Looks right to me. It is strongly encouraged on Chemistry.SE to answer your own question in a formal answer rather than an edit. This will help others to find the right answer if they have a similar question. You could also possibly earn the Self-Lerner badge! Just show any work that you did to get the right equation. Also you should use the proper formatting, which you can read more about here. It's really not that difficult. I will also edit your question so you have another example. Feb 19, 2017 at 1:58
• Thank you sir for helping me with the formatting ! I didn't know that I can answer my own question, I'll try this Feb 19, 2017 at 7:31

My apologizes, I found the answer. The full equation is :
$$\ce{Cu + 4KNO3 + 4HCl -> Cu(NO3)2 + 2NO2 + 4KCl + 2H2O}$$
(I'll detail this later)

• Why not CuCl2 and KNO3, more likely because chloride is a better complexant than nitrate. Write out the ionic equation. Aug 11, 2023 at 22:34
• What happens if all the nitrate is reacted? balance the equation then. The equation is bogus. Aug 12, 2023 at 8:04

Copper reacts in more concentrated nitric acid to give NO2 and possibly some NO depending on concentration. What happens in the above scenario depends on the concentrations of H+, equal at first to Cl-, Cl-, and NO3-; K+ balances the charge. If the amount of hydrochloric acid is enough, the process makes a mild aqua regia. Such solutions use the complexing ability of chloride to facilitate oxidation by nitrate. [with also the possible formation of Cl2]

In nitric acid: Cu + 2NO3- + 4H+ = Cu++ + 2NO2 + 2H2O

With sufficient chloride ion: Cu + 2NO3- +4H+ + Cl- = CuCl+ + 2NO2 + 2H2O

An ultraviolet-visible spectrum should define what is going on. [Possibly just observing the solution would be sufficient.]