What will be the products of the reaction between a metal (i.e. zinc) and a solution containing two dilute acids i.e. HNO3 and H2SO4? [closed]








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The metal is dipped into a beaker that has the two acids, sulphuric (VI) acid and nitric (V) acid in equal concentrations.
In my preliminary research, I found that there might be several possibilities. I disregarded the case of the nitrating mixture since in this case the acids are dilute. There might be formation of a double salt, zinc sulphate nitrate, or formation of the individual salts, zinc sulphate and zinc nitrate with preference to zinc sulphate, the stronger acid. I would like to ask which of these, if any, describe the fate of the reaction.




**The reaction of zinc with dilute sulphuric acid**


Adding zinc plate to dilute sulphuric acid results in metal dissolution with the formation of colourless solution and the release of gas bubbles according to the following reaction: $$\ce{Zn(s) + H2SO4(aq) -> ZnSO4(aq) + H2(g)}$$
**The reaction of zinc with dilute nitric acid**


Products of the reaction between zinc and nitric acid directly depends on the concentration of the latter. Being very dilute nitric acid dissolves zinc without releasing gas: $$\ce{4Zn(s) + 10HNO3(aq) -> 4Zn(NO3)2(aq) + NH4NO3(aq) + 3H2O(l)}$$
A slight increase in the concentration of nitric acid may lead to the liberation of a gas: $$\ce{4Zn(s) + 10HNO3(aq) -> 4Zn(NO3)2(aq) + N2O(g) + 5H2O(l)}$$
**References**


1. Ronald L. Rich. *Inorganic Reaction in Water (1st ed.)*: "Oxidized nitrogen", p. 290.
2. C.E. Housecroft, A.G. Sharpe. *Inorganic Chemistry*: "21.13 Group 12: zinc", p. 771.
3. [Demonstration #1 of the reaction between zinc and dilute sulphuric acid](https://www.youtube.com/watch?v=WGx55g0YYm4).
4. [Demonstration #2 of the reaction between zinc and dilute sulphuric acid](https://www.youtube.com/watch?v=1tn6Q6rxs-w).
5. [Demonstration #3 of the reaction between zinc and dilute nitric acid](https://www.youtube.com/watch?v=8cj0n6b8ItA).


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I find this question merits discussing as there is some difference in the usual simple academic provided answer and actually what occurs in reality.


This likely high school test level question is based on the usual ascribed simplistic renditions of the underlying chemistry. Namely, these dilute acids do not interact with each other, the action of sulphuric with zinc metal results in sulfate and just molecular hydrogen (not exactly accurate) and the nitric acid renders nitrate and somehow (not generally discussed) creates also Laughing Gas. However, this likely suffice as an acceptable answer at this level.


The more accurate advanced answer involves surface chemistry (obviously not likely appropriate at this academic level) where the hydrogen is chemisorbed onto the zinc metal surface as an active hydrogen atom or so-called the $\ce{.H}$ radical, where radical-based chemistry is also an advanced topic. The latter $\ce{.H}$ continues via surface interaction beginning with the aqueous nitrate ion leading to nitric oxides ($\ce{.NO2}$ and $\ce{.NO}$) formation in dilute solutions, and finally the $\ce{.HNO}$ radical. The latter can self react creating hyponitrous acid ($\ce{H2N2O2}$), which being unstable, further breaks down liberating the generally only final cited gaseous product (for simplicity) namely, just Laughing Gas ($\ce{N2O}$).


Interestingly, the interaction of hydrogen and zinc metal is also of concern in [corrosion studies](https://www.corrosionpedia.com/a-failure-analysis-of-hydrogen-embrittlement-in-bridge-fasteners/2/6877), to quote: "Corrosion of the zinc generated the hydrogen causing the embrittlement". Also, $\ce{.H}$ radical functionally behaves, per its seemingly reversible formation reaction: $\ce{e- + H+ = .H}$ as apparently a $\ce{(e-,H+)}$ pair acting on ions. For example, per ['Hydrometallurgy 2008: Proceedings of the Sixth International Symposium'](https://books.google.com/books?id=1etfSdk55SYC&pg=PA818&lpg=PA818&dq=what+metals+react+with+hcl+to+form+nascent+hydrogen&source=bl&ots=yEBZaIFL_T&sig=9383ZW7NCXAoSNmmny2sdrxXIF0&hl=en&sa=X&ved=0ahUKEwjEjpnWjejaAhVP4VMKHe1gBZE4FBDoAQg6MAU#v=onepage&q=what%20metals%20react%20with%20hcl%20to%20form%20nascent%20hydrogen&f=false), from Page 818, to quote:



> 
> $\ce{ PbS + 2 •H = Pb + H2S (5) }$
> 
> 
> 


as a proposed commercial reductive leaching reaction and, in the case of zinc with acid acting on aqueous nitrate, one of the reactions:



> 
> $\ce{ NO3- + •H = OH- + •NO2 }$
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> 
> 


in accord with Maurice's comment.


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