Why doesn't $\ce{NO}$ (nitric oxide) react with water? I know it is a neutral oxide, but I'm really curious as to why that is. Why will $\ce{NO}$ not react with $\ce{H2O}$?
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6$\begingroup$ Why would it? Normally we explain why things happen, and not why they don't. $\endgroup$– Ivan NeretinMar 22, 2017 at 22:31
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$\begingroup$ Think about it, oxides dissolve in water to give their corresponding acids or bases. Here, what acid would you get, and how stable would its conjugate base ? i believe now you have your answer $\endgroup$– SubZeroMar 23, 2017 at 7:26
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3$\begingroup$ @IvanNeretin what is "normal"? $\endgroup$– ParaH2Mar 23, 2017 at 8:22
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2 Answers
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Although nitric oxide is thermodynamically unstable, it is kinetically stable as its decomposition rate is very slow[ref] and so it is considered stable and won't normally react to anything.
So, nitric oxide wouldn't normally hydrolyze easily. But in the presence of air, it forms nitrous acid $(\ce{HONO})$:
$$\ce{4NO + O2 + 2 H2O -> 4 HNO2}$$
However, nitrous acid is very unstable and quickly disproportionates:
$$ \begin{align} \ce{2 HNO2 &-> NO2 + NO + H2O &(cold dil. soln.)}\\ \ce{3 HNO2 &-> HNO3 + 2 NO + H2O &(warm conc. soln.)} \end{align}$$
Since $\ce{HNO2}$ is required to prepare diazonium salts (a versatile compound in organic chemistry), it is prepared in-situ by reaction of $\ce{NaNO2}$ and $\ce{HCl}$. Due to its instability, it is prepared for one-time use and is not stored for further preparations.
Reference: J. Phys. Chem., 1958, 62 (3), pp 360–361 https://doi.org/10.1021/j150561a030
answered Apr 8, 2017 at 6:59
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I have also heard about a disproportion reaction which happens with a productivity of around $0,01 \%$ as,
$$\ce{4NO + H2O -> N2O + 2HNO2}$$
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$\begingroup$ Hi thanks for your contribution. Though in such cases, it's much better to cite your source as well. A research paper or a famous textbook generally works. Thanks! $\endgroup$ Apr 24, 2018 at 9:16
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$\begingroup$ My chemistry teacher, a professor at my university told me about this reaction a long long time ago. Since then the only source where I could find this reaction was a Russian website which also contains a vast database of known chemical reactions. There is no original source, there's a mistake (HNO3 instead of HNO2) and the only note is "almost no reaction". Sorry, it's a really interesting reaction and I keep wondering about its mechanism but I just fail to find any papers or books, at least on the Internet. $\endgroup$ Apr 24, 2018 at 23:03
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$\begingroup$ No worries, and I appreciate your response. But in this case, I think it's rather better if you instead ask a new question, looking for proper citation for the reaction. We support reference-request as well, so it wouldn't be a problem :-) $\endgroup$ Apr 25, 2018 at 0:23