What are the Lewis dot formulae for sulfuric and nitric acids?

1 Answer
Dec 28, 2015

Both sulfuric and nitric acids are NEUTRAL species. Lewis dot formulae should (and do) reflect this neutrality.


Typically, we would display the sulfur in sulfuric acid as a neutral species, with 2 #S=O# bonds. Thus, we would get the Lewis structure: #(HO)S(=O)_2(OH)#. Alternatively, we could represent charge separation: #(HO)S^(2+)(-O^(-))_2(OH)#, which is arguably a better representation.

On the other hand, nitric acid MUST display a quaternized nitrogen (i.e. formally positive), and a formally negative oxygen charge: #HO-N^+(=O)O^-#.

All of these Lewis structures are representations of actual NEUTRAL and ISOLABLE molecules. The Lewis structures that I have tried to represent are conceptual, and may or may not represent chemical reality.

Neither Lewis representation will indicate how or why sulfuric acid is a stronger acid than nitric acid. This is an experimental phenomenon, and is not dependent our Lewis representations. In fact, sulfuric acid is a stronger acid than nitric acid, and will protonate nitric acid to give the #NO_2^+# cation:

#H_2SO_4 + HNO_3 rarr NO_2^+ + HSO_4^(-) + H_2O#

I've forgotten what you call the #NO_2^+# cation! It might come to me presently. Ah, it's the nitronium ion.