# Acidic strength of oxides of nitrogen

Why do we compare acidic strength of oxides of nitrogen even though they don't have hydrogen?

• Welcome to chemistry.SE! If you had any questions about the policies of our community, please ‎visit the help center. || It would be helpful if you tell us what your background is. Have you studied Lewis or Bronsted theories of acids and bases? – It's Over Aug 29 '15 at 11:44
• I am a student, Yes I have studied about the acids you mentioned but don't understand them – ashwini abhishek Aug 29 '15 at 12:46

Compounds containing hydrogen are not only acidic but we have other concepts also. Like in your case it can be explained through Lewis acid-base concept.

Lewis concept: A base is defined as a substance which can furnish a pair of electrons to form a coordinate bond whereas an acid is a substance which can accept a pair of electron.

For example, $\ce{NH3}$ is a Lewis base since on nitrogen we have one electron pair which easily be donated to form a coordinate bond. As for acid, Take any two oxides of nitrogen for example $\ce{NO2}$ and $\ce{N2O5}$ . First check the oxidation state of nitrogen in two cases, here it is +4 and +5 . Since a substance which can accept a pair of electrons is an acid, so the nitrogen with more positive oxidation state will relatively accept pair of electrons with more easily, therefore $\ce{N2O5}$ is a better acid then $\ce{NO2}$.

• It would be helpful if you elaborate a bit about what Bronsted and Lewis definitions are, possibly with some references. – It's Over Oct 9 '15 at 0:33
• This answer is wrong you'd need Lux-Flood theory for oxides, not Lewis – Mithoron Dec 13 '15 at 13:54
• @Mithoron lux-flood theory is applicable only if both the reacting species are oxides right? – ShankRam Feb 12 '16 at 7:31
• Don't see why you need Lux-Flood as when an oxide ion is accepted it can also be seen as accepting an electron pair from the oxide ion. Isn't Lux-Flood just a subset of Lewis? – Ian Bush Apr 11 '16 at 15:43