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

1 Answer
Dec 28, 2015

Answer:

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

Explanation:

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.